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</div> <div class="control"> <button class="button is-small is-link">Go</button> </div> </div> </form> </div> </div> <nav class="pagination is-small is-centered breathe-horizontal" role="navigation" aria-label="pagination"> <a href="" class="pagination-previous is-invisible">Previous </a> <a href="/search/?searchtype=author&query=Matarrese%2C+S&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Matarrese%2C+S&start=0" class="pagination-link is-current" aria-label="Goto page 1">1 </a> </li> <li> <a href="/search/?searchtype=author&query=Matarrese%2C+S&start=50" class="pagination-link " aria-label="Page 2" aria-current="page">2 </a> </li> <li> <a href="/search/?searchtype=author&query=Matarrese%2C+S&start=100" class="pagination-link " aria-label="Page 3" aria-current="page">3 </a> </li> </ul> </nav> <ol class="breathe-horizontal" start="1"> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2502.20137">arXiv:2502.20137</a> <span> [<a href="https://arxiv.org/pdf/2502.20137">pdf</a>, <a href="https://arxiv.org/format/2502.20137">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> </div> </div> <p class="title is-5 mathjax"> Scalar-Induced Gravitational Waves in Modified Gravity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Kugarajh%2C+A+A">Anjali Abirami Kugarajh</a>, <a href="/search/gr-qc?searchtype=author&query=Traforetti%2C+M">Marisol Traforetti</a>, <a href="/search/gr-qc?searchtype=author&query=Maselli%2C+A">Andrea Maselli</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Ricciardone%2C+A">Angelo Ricciardone</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2502.20137v1-abstract-short" style="display: inline;"> Scalar-Induced Gravitational Waves (SIGWs), second-order tensor modes sourced by first-order scalar fluctuations in General Relativity (GR), are expected to contribute to the Stochastic Gravitational Wave Background (SGWB) potentially detectable by current and future gravitational wave interferometers. In the framework of GR, this SGWB represents an unavoidable contribution to the gravitational wa… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2502.20137v1-abstract-full').style.display = 'inline'; document.getElementById('2502.20137v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2502.20137v1-abstract-full" style="display: none;"> Scalar-Induced Gravitational Waves (SIGWs), second-order tensor modes sourced by first-order scalar fluctuations in General Relativity (GR), are expected to contribute to the Stochastic Gravitational Wave Background (SGWB) potentially detectable by current and future gravitational wave interferometers. In the framework of GR, this SGWB represents an unavoidable contribution to the gravitational wave spectrum. In this paper, we go beyond GR and we investigate the behavior of SIGWs in f(R) gravity. We explore how the SIGW spectrum is influenced across a broad range of frequencies, from the nano-Hz regime, where the Pulsar Timing Array (PTA) operates, through the milli-Hz band probed by the space-based LISA detector, up to the kilo-Hz frequency range, where the ground-based LIGO/Virgo/KAGRA network is currently operational. Our results indicate that the beyond-GR correction leaves an observational imprint, mainly in the low-frequency part of the spectrum, giving the possibility to use SIGW to constrain GR on scales on which we have limited information. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2502.20137v1-abstract-full').style.display = 'none'; document.getElementById('2502.20137v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 27 February, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2025. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2501.13678">arXiv:2501.13678</a> <span> [<a href="https://arxiv.org/pdf/2501.13678">pdf</a>, <a href="https://arxiv.org/format/2501.13678">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> Exploring gravitational impulse via quantum Boltzmann equation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Sharifian%2C+M">Mohammad Sharifian</a>, <a href="/search/gr-qc?searchtype=author&query=Zarei%2C+M">Moslem Zarei</a>, <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">Nicola Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2501.13678v1-abstract-short" style="display: inline;"> We investigate the gravitational impulse by using the generalized formulation of the quantum Boltzmann equation (QBE), wherein the initial states are taken as wave packets rather than plane waves. The QBE equation operates within an open quantum system framework. Using this approach, we can analyze the two-body gravitational scattering by considering one body as part of the environment and the oth… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2501.13678v1-abstract-full').style.display = 'inline'; document.getElementById('2501.13678v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2501.13678v1-abstract-full" style="display: none;"> We investigate the gravitational impulse by using the generalized formulation of the quantum Boltzmann equation (QBE), wherein the initial states are taken as wave packets rather than plane waves. The QBE equation operates within an open quantum system framework. Using this approach, we can analyze the two-body gravitational scattering by considering one body as part of the environment and the other as the system. Similarly, we apply this approach to the gravitational impulse of a photon due to a massive object, during which we consider the photon as the system and the massive object as the environment. In this methodology, we use the forward scattering term of the extended QBE to compute the time evolution of the momentum operator associated with the system. While this term vanishes when considering point particles, we demonstrate its persistence when using wave packets to describe both massive particles and the photon field. Through this procedure, we obtain the leading order of the system's impulse. The results reported here are entirely consistent with the previous approaches. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2501.13678v1-abstract-full').style.display = 'none'; document.getElementById('2501.13678v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 January, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2025. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">27 pages, 2 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2412.15654">arXiv:2412.15654</a> <span> [<a href="https://arxiv.org/pdf/2412.15654">pdf</a>, <a href="https://arxiv.org/format/2412.15654">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> </div> <p class="title is-5 mathjax"> Non-linear effects on the Cosmological Gravitational Wave Background anisotropies </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Mierna%2C+A">Alina Mierna</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">Nicola Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Ricciardone%2C+A">Angelo Ricciardone</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2412.15654v1-abstract-short" style="display: inline;"> The Cosmological Gravitational Wave Background (CGWB) anisotropies contain valuable information about the physics of the early universe. Given that General Relativity is intrinsically nonlinear, it is important to look beyond first-order contributions in cosmological perturbations. In this work, we present a non-perturbative approach for the computation of CGWB anisotropies at large scales, provid… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2412.15654v1-abstract-full').style.display = 'inline'; document.getElementById('2412.15654v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2412.15654v1-abstract-full" style="display: none;"> The Cosmological Gravitational Wave Background (CGWB) anisotropies contain valuable information about the physics of the early universe. Given that General Relativity is intrinsically nonlinear, it is important to look beyond first-order contributions in cosmological perturbations. In this work, we present a non-perturbative approach for the computation of CGWB anisotropies at large scales, providing the extension of the initial conditions and the Sachs-Wolfe effect for the CGWB, which encodes the full non-linearity of the scalar metric perturbations. We also derive the non-perturbative expression for three-point correlation of the gravitational wave energy density perturbation in the case of an inflationary CGWB with a scale-invariant power spectrum and negligible primordial non-Gaussianity. We show that, under such conditions, the gravitational wave energy density perturbations are lognormally distributed, leading to an interesting effect such as intermittency. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2412.15654v1-abstract-full').style.display = 'none'; document.getElementById('2412.15654v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 20 December, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2412.06764">arXiv:2412.06764</a> <span> [<a href="https://arxiv.org/pdf/2412.06764">pdf</a>, <a href="https://arxiv.org/format/2412.06764">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Phenomenology">hep-ph</span> </div> </div> <p class="title is-5 mathjax"> How Well Do We Know the Scalar-Induced Gravitational Waves? </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Iovino%2C+A+J">A. J. Iovino</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">S. Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Perna%2C+G">G. Perna</a>, <a href="/search/gr-qc?searchtype=author&query=Ricciardone%2C+A">A. Ricciardone</a>, <a href="/search/gr-qc?searchtype=author&query=Riotto%2C+A">A. Riotto</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2412.06764v1-abstract-short" style="display: inline;"> Gravitational waves sourced by amplified scalar perturbations are a common prediction across a wide range of cosmological models. These scalar curvature fluctuations are inherently nonlinear and typically non-Gaussian. We argue that the effects of non-Gaussianity may not always be adequately captured by an expansion around a Gaussian field, expressed through nonlinear parameters such as… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2412.06764v1-abstract-full').style.display = 'inline'; document.getElementById('2412.06764v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2412.06764v1-abstract-full" style="display: none;"> Gravitational waves sourced by amplified scalar perturbations are a common prediction across a wide range of cosmological models. These scalar curvature fluctuations are inherently nonlinear and typically non-Gaussian. We argue that the effects of non-Gaussianity may not always be adequately captured by an expansion around a Gaussian field, expressed through nonlinear parameters such as $f_{\rm{NL}}$. As a consequence, the resulting amplitude of the stochastic gravitational wave background may differ significantly from predictions based on the standard quadratic source model routinely used in the literature. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2412.06764v1-abstract-full').style.display = 'none'; document.getElementById('2412.06764v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 9 December, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">4 pages, 2 Figures + Supplementary Material</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2407.09405">arXiv:2407.09405</a> <span> [<a href="https://arxiv.org/pdf/2407.09405">pdf</a>, <a href="https://arxiv.org/format/2407.09405">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> </div> <p class="title is-5 mathjax"> Inflationary Initial Conditions for the Cosmological Gravitational Wave Background </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Dall%27Armi%2C+L+V">Lorenzo Valbusa Dall'Armi</a>, <a href="/search/gr-qc?searchtype=author&query=Mierna%2C+A">Alina Mierna</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Ricciardone%2C+A">Angelo Ricciardone</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2407.09405v1-abstract-short" style="display: inline;"> The initial conditions on the anisotropies of the stochastic gravitational-wave background of cosmological origin (CGWB) largely depend on the mechanism that generates the gravitational waves. Since the CGWB is expected to be non-thermal, the computation of the initial conditions could be more challenging w.r.t. the Cosmic Microwave Background (CMB), whose interactions with other particles in the… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.09405v1-abstract-full').style.display = 'inline'; document.getElementById('2407.09405v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2407.09405v1-abstract-full" style="display: none;"> The initial conditions on the anisotropies of the stochastic gravitational-wave background of cosmological origin (CGWB) largely depend on the mechanism that generates the gravitational waves. Since the CGWB is expected to be non-thermal, the computation of the initial conditions could be more challenging w.r.t. the Cosmic Microwave Background (CMB), whose interactions with other particles in the early Universe lead to a blackbody spectrum. In this paper, we show that the initial conditions for the cosmological background generated by quantum fluctuations of the metric during inflation deviate from adiabaticity. These primordial gravitational waves are indeed generated by quantum fluctuations of two independent degrees of freedom (the two polarization states of the gravitons). Furthermore, the CGWB plays a negligible role in the Einstein's equations, because its energy density is subdominant w.r.t. ordinary matter. Therefore, the only possible way to compute the initial conditions for inflationary gravitons is to perturb the energy-momentum tensor of the gravitational field defined in terms of the small-scale tensor perturbation of the metric. This new and self-consistent approach shows that a large, non-adiabatic initial condition is present even during the single-field inflation. Such a contribution enhances the total angular power spectrum of the CGWB compared to the standard adiabatic case, increasing also the sensitivity of the anisotropies to the presence of relativistic and decoupled particles in the early Universe. In this work we have also proved that our findings are quite general and apply to both single-field inflation and other scenarios in which the CGWB is generated by the quantum fluctuations of the metric, like the curvaton. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.09405v1-abstract-full').style.display = 'none'; document.getElementById('2407.09405v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 July, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication on JCAP. arXiv admin note: text overlap with arXiv:2307.11043</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2405.20208">arXiv:2405.20208</a> <span> [<a href="https://arxiv.org/pdf/2405.20208">pdf</a>, <a href="https://arxiv.org/format/2405.20208">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> </div> <p class="title is-5 mathjax"> Proper time path integrals for gravitational waves: an improved wave optics framework </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Braga%2C+G">Ginevra Braga</a>, <a href="/search/gr-qc?searchtype=author&query=Garoffolo%2C+A">Alice Garoffolo</a>, <a href="/search/gr-qc?searchtype=author&query=Ricciardone%2C+A">Angelo Ricciardone</a>, <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">Nicola Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2405.20208v1-abstract-short" style="display: inline;"> When gravitational waves travel from their source to an observer, they interact with matter structures along their path, causing distinct deformations in their waveforms. In this study we introduce a novel theoretical framework for wave optics effects in gravitational lensing, addressing the limitations of existing approaches. We achieve this by incorporating the proper time technique, typically u… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.20208v1-abstract-full').style.display = 'inline'; document.getElementById('2405.20208v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2405.20208v1-abstract-full" style="display: none;"> When gravitational waves travel from their source to an observer, they interact with matter structures along their path, causing distinct deformations in their waveforms. In this study we introduce a novel theoretical framework for wave optics effects in gravitational lensing, addressing the limitations of existing approaches. We achieve this by incorporating the proper time technique, typically used in field theory studies, into gravitational lensing. This approach allows us to extend the standard formalism beyond the eikonal and paraxial approximations, which are traditionally assumed, and to account for polarization effects, which are typically neglected in the literature. We demonstrate that our method provides a robust generalization of conventional approaches, including them as special cases. Our findings enhance our understanding of gravitational wave propagation, which is crucial for accurately interpreting gravitational wave observations and extracting unbiased information about the lenses from the gravitational wave waveforms. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.20208v1-abstract-full').style.display = 'none'; document.getElementById('2405.20208v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 30 May, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">31 pages plus technical appendices, 4 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2403.06962">arXiv:2403.06962</a> <span> [<a href="https://arxiv.org/pdf/2403.06962">pdf</a>, <a href="https://arxiv.org/format/2403.06962">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> </div> <p class="title is-5 mathjax"> Fully non-Gaussian Scalar-Induced Gravitational Waves </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Perna%2C+G">Gabriele Perna</a>, <a href="/search/gr-qc?searchtype=author&query=Testini%2C+C">Chiara Testini</a>, <a href="/search/gr-qc?searchtype=author&query=Ricciardone%2C+A">Angelo Ricciardone</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2403.06962v1-abstract-short" style="display: inline;"> Scalar-induced Gravitational Waves (SIGWs) represent a particular class of primordial signals which are sourced at second-order in perturbation theory whenever a scalar fluctuation of the metric is present. They form a guaranteed Stochastic Gravitational Wave Background (SGWB) that, depending on the amplification of primordial scalar fluctuations, can be detected by GW detectors. The amplitude and… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2403.06962v1-abstract-full').style.display = 'inline'; document.getElementById('2403.06962v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2403.06962v1-abstract-full" style="display: none;"> Scalar-induced Gravitational Waves (SIGWs) represent a particular class of primordial signals which are sourced at second-order in perturbation theory whenever a scalar fluctuation of the metric is present. They form a guaranteed Stochastic Gravitational Wave Background (SGWB) that, depending on the amplification of primordial scalar fluctuations, can be detected by GW detectors. The amplitude and the frequency shape of the scalar-induced SGWB can be influenced by the statistical properties of the scalar density perturbations. In this work we study the intuitive physics behind SIGWs and we analyze the imprints of local non-Gaussianity of the primordial curvature perturbation on the GW spectrum. We consider all the relevant non-Gaussian contributions up to fifth-order in the scalar seeds without any hierarchy, and we derive the related GW energy density $惟_{\rm GW}(f)$. We perform a Fisher matrix analysis to understand to which accuracy non-Gaussianity can be constrained with the LISA detector, which will be sensitive in the milli-Hertz frequency band. We find that LISA, neglecting the impact of astrophysical foregrounds, will be able to measure the amplitude, the width and the peak of the spectrum with an accuracy up to $\mathcal{O}(10^{-4})$, while non-Gaussianity can be measured up to $\mathcal{O}(10^{-3})$. Finally, we discuss the implications of our non-Gaussianity expansion on the fraction of Primordial Black Holes. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2403.06962v1-abstract-full').style.display = 'none'; document.getElementById('2403.06962v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 11 March, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">39 pages, 23 figures + Appendices</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2312.00717">arXiv:2312.00717</a> <span> [<a href="https://arxiv.org/pdf/2312.00717">pdf</a>, <a href="https://arxiv.org/format/2312.00717">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2024/06/008">10.1088/1475-7516/2024/06/008 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> LiteBIRD Science Goals and Forecasts. A Case Study of the Origin of Primordial Gravitational Waves using Large-Scale CMB Polarization </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Campeti%2C+P">P. Campeti</a>, <a href="/search/gr-qc?searchtype=author&query=Komatsu%2C+E">E. Komatsu</a>, <a href="/search/gr-qc?searchtype=author&query=Baccigalupi%2C+C">C. Baccigalupi</a>, <a href="/search/gr-qc?searchtype=author&query=Ballardini%2C+M">M. Ballardini</a>, <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">N. Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Carones%2C+A">A. Carones</a>, <a href="/search/gr-qc?searchtype=author&query=Errard%2C+J">J. Errard</a>, <a href="/search/gr-qc?searchtype=author&query=Finelli%2C+F">F. Finelli</a>, <a href="/search/gr-qc?searchtype=author&query=Flauger%2C+R">R. Flauger</a>, <a href="/search/gr-qc?searchtype=author&query=Galli%2C+S">S. Galli</a>, <a href="/search/gr-qc?searchtype=author&query=Galloni%2C+G">G. Galloni</a>, <a href="/search/gr-qc?searchtype=author&query=Giardiello%2C+S">S. Giardiello</a>, <a href="/search/gr-qc?searchtype=author&query=Hazumi%2C+M">M. Hazumi</a>, <a href="/search/gr-qc?searchtype=author&query=Henrot-Versill%C3%A9%2C+S">S. Henrot-Versill茅</a>, <a href="/search/gr-qc?searchtype=author&query=Hergt%2C+L+T">L. T. Hergt</a>, <a href="/search/gr-qc?searchtype=author&query=Kohri%2C+K">K. Kohri</a>, <a href="/search/gr-qc?searchtype=author&query=Leloup%2C+C">C. Leloup</a>, <a href="/search/gr-qc?searchtype=author&query=Lesgourgues%2C+J">J. Lesgourgues</a>, <a href="/search/gr-qc?searchtype=author&query=Macias-Perez%2C+J">J. Macias-Perez</a>, <a href="/search/gr-qc?searchtype=author&query=Mart%C3%ADnez-Gonz%C3%A1lez%2C+E">E. Mart铆nez-Gonz谩lez</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">S. Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Matsumura%2C+T">T. Matsumura</a>, <a href="/search/gr-qc?searchtype=author&query=Montier%2C+L">L. Montier</a>, <a href="/search/gr-qc?searchtype=author&query=Namikawa%2C+T">T. Namikawa</a>, <a href="/search/gr-qc?searchtype=author&query=Paoletti%2C+D">D. Paoletti</a> , et al. (85 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2312.00717v2-abstract-short" style="display: inline;"> We study the possibility of using the $LiteBIRD$ satellite $B$-mode survey to constrain models of inflation producing specific features in CMB angular power spectra. We explore a particular model example, i.e. spectator axion-SU(2) gauge field inflation. This model can source parity-violating gravitational waves from the amplification of gauge field fluctuations driven by a pseudoscalar "axionlike… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.00717v2-abstract-full').style.display = 'inline'; document.getElementById('2312.00717v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2312.00717v2-abstract-full" style="display: none;"> We study the possibility of using the $LiteBIRD$ satellite $B$-mode survey to constrain models of inflation producing specific features in CMB angular power spectra. We explore a particular model example, i.e. spectator axion-SU(2) gauge field inflation. This model can source parity-violating gravitational waves from the amplification of gauge field fluctuations driven by a pseudoscalar "axionlike" field, rolling for a few e-folds during inflation. The sourced gravitational waves can exceed the vacuum contribution at reionization bump scales by about an order of magnitude and can be comparable to the vacuum contribution at recombination bump scales. We argue that a satellite mission with full sky coverage and access to the reionization bump scales is necessary to understand the origin of the primordial gravitational wave signal and distinguish among two production mechanisms: quantum vacuum fluctuations of spacetime and matter sources during inflation. We present the expected constraints on model parameters from $LiteBIRD$ satellite simulations, which complement and expand previous studies in the literature. We find that $LiteBIRD$ will be able to exclude with high significance standard single-field slow-roll models, such as the Starobinsky model, if the true model is the axion-SU(2) model with a feature at CMB scales. We further investigate the possibility of using the parity-violating signature of the model, such as the $TB$ and $EB$ angular power spectra, to disentangle it from the standard single-field slow-roll scenario. We find that most of the discriminating power of $LiteBIRD$ will reside in $BB$ angular power spectra rather than in $TB$ and $EB$ correlations. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.00717v2-abstract-full').style.display = 'none'; document.getElementById('2312.00717v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 March, 2025; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 1 December, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">22 pages, 13 figures. Published in JCAP 06 (2024) 008. Added comments at end of Sec. 6 reframing conclusions in more general way. Updated references</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> JCAP 06 (2024), 008 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2311.01445">arXiv:2311.01445</a> <span> [<a href="https://arxiv.org/pdf/2311.01445">pdf</a>, <a href="https://arxiv.org/format/2311.01445">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Phenomenology">hep-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2024/04/069">10.1088/1475-7516/2024/04/069 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Induced Circular Polarization on Photons Due to Interaction with Axion-Like Particles in Rotating Magnetic Field of Neutron Stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Sharifian%2C+M">Mohammad Sharifian</a>, <a href="/search/gr-qc?searchtype=author&query=Zarei%2C+M">Moslem Zarei</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Turolla%2C+R">Roberto Turolla</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2311.01445v2-abstract-short" style="display: inline;"> We investigate how the photon polarization is affected by the interaction with axion-like particles (ALPs) in the rotating magnetic field of a neutron star (NS). Using quantum Boltzmann equations the study demonstrates that the periodic magnetic field of millisecond NSs enhances the interaction of photons with ALPs and creates a circular polarization on them. A binary system including an NS and a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.01445v2-abstract-full').style.display = 'inline'; document.getElementById('2311.01445v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2311.01445v2-abstract-full" style="display: none;"> We investigate how the photon polarization is affected by the interaction with axion-like particles (ALPs) in the rotating magnetic field of a neutron star (NS). Using quantum Boltzmann equations the study demonstrates that the periodic magnetic field of millisecond NSs enhances the interaction of photons with ALPs and creates a circular polarization on them. A binary system including an NS and a companion star could serve as a probe. When the NS is in front of the companion star with respect to the earth observer, there is a circular polarization on the previously linearly polarized photons as a result of the interaction with ALPs there. After a half-binary period, the companion star passes in front of the NS, and the circular polarization of photons disappears and changes to linear. The excluded parameter space for a millisecond NS with 300~Hz rotating frequency, highlights the coupling constant of $1.7\times10^{-11}~\text{GeV}^{-1}\leq g_{a纬纬}\leq1.6\times10^{-3}~\text{GeV}^{-1}$ for the ALP masses in the range of $7\times10^{-12}~\text{eV}\leq m_a\leq1.5\times 10^{3}~\text{eV}$. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.01445v2-abstract-full').style.display = 'none'; document.getElementById('2311.01445v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 April, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 2 November, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">33 pages, 5 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> JCAP04(2024)069 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2309.13112">arXiv:2309.13112</a> <span> [<a href="https://arxiv.org/pdf/2309.13112">pdf</a>, <a href="https://arxiv.org/format/2309.13112">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Phenomenology">hep-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2024/04/058">10.1088/1475-7516/2024/04/058 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Anharmonic Effects on the Squeezing of Axion Perturbations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Danieli%2C+V">Valentina Danieli</a>, <a href="/search/gr-qc?searchtype=author&query=Kobayashi%2C+T">Takeshi Kobayashi</a>, <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">Nicola Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Viel%2C+M">Matteo Viel</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2309.13112v2-abstract-short" style="display: inline;"> It is assumed in standard cosmology that the Universe underwent a period of inflation in its earliest phase, providing the seeds for structure formation through vacuum fluctuations of the inflaton scalar field. These fluctuations get stretched by the quasi-exponential expansion of the Universe and become squeezed. The aim of this paper is to deepen the understanding of the squeezing process, consi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.13112v2-abstract-full').style.display = 'inline'; document.getElementById('2309.13112v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2309.13112v2-abstract-full" style="display: none;"> It is assumed in standard cosmology that the Universe underwent a period of inflation in its earliest phase, providing the seeds for structure formation through vacuum fluctuations of the inflaton scalar field. These fluctuations get stretched by the quasi-exponential expansion of the Universe and become squeezed. The aim of this paper is to deepen the understanding of the squeezing process, considering the effect of self-interactions. Axion-like particles can provide a useful setup to study this effect. Specifically we focus on the consequences that a non-trivial evolution of the background axion field has on the squeezing of the perturbations. We follow the evolution of the axion's fluctuation modes from the horizon exit during inflation to the radiation-dominated epoch. We compute Bogoliubov coefficients and squeezing parameters, which are linked to the axion particle number and isocurvature perturbation. We find that the quantum mechanical particle production and the squeezing of the perturbations are enhanced, if one accounts for anharmonic effects, i.e., the effect of higher order terms in the potential. This effect becomes particularly strong towards the hilltop of the potential. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.13112v2-abstract-full').style.display = 'none'; document.getElementById('2309.13112v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 18 April, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 22 September, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">22 pages + appendices, 10 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> JCAP04(2024)058 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2309.07236">arXiv:2309.07236</a> <span> [<a href="https://arxiv.org/pdf/2309.07236">pdf</a>, <a href="https://arxiv.org/format/2309.07236">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.109.043510">10.1103/PhysRevD.109.043510 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Open Quantum System Approach to the Gravitational Decoherence of Spin-1/2 Particles </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Sharifian%2C+M">Mohammad Sharifian</a>, <a href="/search/gr-qc?searchtype=author&query=Zarei%2C+M">Moslem Zarei</a>, <a href="/search/gr-qc?searchtype=author&query=Abdi%2C+M">Mehdi Abdi</a>, <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">Nicola Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2309.07236v2-abstract-short" style="display: inline;"> This paper investigates the decoherence effect resulting from the interaction of squeezed gravitational waves with a system of massive particles in spatial superposition. This paper investigates the decoherence effect resulting from the interaction of squeezed gravitational waves with a system of massive particles in spatial superposition. We first employ the open quantum system approach to obtain… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.07236v2-abstract-full').style.display = 'inline'; document.getElementById('2309.07236v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2309.07236v2-abstract-full" style="display: none;"> This paper investigates the decoherence effect resulting from the interaction of squeezed gravitational waves with a system of massive particles in spatial superposition. This paper investigates the decoherence effect resulting from the interaction of squeezed gravitational waves with a system of massive particles in spatial superposition. We first employ the open quantum system approach to obtain the established decoherence in a spatial superposition of massive objects induced by squeezed gravitational waves. Subsequently, we focus on the spin-1/2 particle system, and our analysis reveals that the decoherence rate depends on both the squeezing strength and the squeezing angle of the gravitational waves. Our results demonstrate that squeezed gravitational waves with squeezing strengths of $r_p\geq1.2$ and a squeezing angle of $\varphi_p=蟺/2$ can induce a 1 % decoherence within 1 s free falling of a cloud of spin-1/2 particles. This investigation sheds light on the relationship between squeezed gravitational waves and the coherence of spatial superposition states in systems of massive particles and their spin. The dependence of decoherence on squeezing strength and, in the case of spin-$1/2$ particles, on the squeezing angle paves the way for further exploration and understanding of the quantum-gravity connection. We suggest that such an experimental setup could also be employed to eventually investigate the level of squeezing effect (and hence quantum-related properties) of gravitational waves produced in the early universe from inflation. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.07236v2-abstract-full').style.display = 'none'; document.getElementById('2309.07236v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 February, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 12 September, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">44 pages, 8 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 109, 043510 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2307.11043">arXiv:2307.11043</a> <span> [<a href="https://arxiv.org/pdf/2307.11043">pdf</a>, <a href="https://arxiv.org/format/2307.11043">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> </div> <p class="title is-5 mathjax"> Adiabatic or Non-Adiabatic? Unraveling the Nature of Initial Conditions in the Cosmological Gravitational Wave Background </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Dall%27Armi%2C+L+V">Lorenzo Valbusa Dall'Armi</a>, <a href="/search/gr-qc?searchtype=author&query=Mierna%2C+A">Alina Mierna</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Ricciardone%2C+A">Angelo Ricciardone</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2307.11043v1-abstract-short" style="display: inline;"> The non-thermal nature of the stochastic gravitational-wave background of cosmological origin (CGWB) poses a challenge in defining the initial conditions for the graviton overdensity. Specifically, the adiabatic initial condition, which holds for Cosmic Microwave Background (CMB) photons, is not guaranteed a priori for the primordial GWs. In this letter, we compute the initial conditions for the c… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2307.11043v1-abstract-full').style.display = 'inline'; document.getElementById('2307.11043v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2307.11043v1-abstract-full" style="display: none;"> The non-thermal nature of the stochastic gravitational-wave background of cosmological origin (CGWB) poses a challenge in defining the initial conditions for the graviton overdensity. Specifically, the adiabatic initial condition, which holds for Cosmic Microwave Background (CMB) photons, is not guaranteed a priori for the primordial GWs. In this letter, we compute the initial conditions for the cosmological background generated by quantum fluctuations of the metric during inflation. Our analysis reveals that adiabatic initial conditions are no longer valid. The violation of adiabaticity arises from the presence of independent tensor perturbations during inflation, which behave as two extra fields that affect the standard single-clock argument. Since the energy density of the CGWB is subdominant compared to ordinary matter, gravitational radiation plays a negligible role in Einstein's equations. Therefore, the only way to compute the initial conditions is to perturb the energy-momentum tensor defined in terms of the gravitational strain. A direct consequence of our finding is that the initial conditions from inflation enhance the total CGWB angular power-spectrum by an order of magnitude compared to the standard adiabatic case. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2307.11043v1-abstract-full').style.display = 'none'; document.getElementById('2307.11043v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 20 July, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">7 pages, 1 figure</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2307.05404">arXiv:2307.05404</a> <span> [<a href="https://arxiv.org/pdf/2307.05404">pdf</a>, <a href="https://arxiv.org/format/2307.05404">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.109.023509">10.1103/PhysRevD.109.023509 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Gravitational waves induced by scalar-tensor mixing </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Bari%2C+P">Pritha Bari</a>, <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">Nicola Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Dom%C3%A8nech%2C+G">Guillem Dom猫nech</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2307.05404v2-abstract-short" style="display: inline;"> This paper explores the physics of second-order gravitational waves (GWs) induced by scalar-tensor perturbation interactions in the radiation-dominated Universe. We investigate the distinctive signatures of these GWs and their detectability compared to scalar-induced GWs. Unlike scalar-scalar induced GWs, scalar-tensor induced GWs do not present resonances or a logarithmic running in the low frequ… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2307.05404v2-abstract-full').style.display = 'inline'; document.getElementById('2307.05404v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2307.05404v2-abstract-full" style="display: none;"> This paper explores the physics of second-order gravitational waves (GWs) induced by scalar-tensor perturbation interactions in the radiation-dominated Universe. We investigate the distinctive signatures of these GWs and their detectability compared to scalar-induced GWs. Unlike scalar-scalar induced GWs, scalar-tensor induced GWs do not present resonances or a logarithmic running in the low frequency tail in the case of peaked primordial spectra. But, interestingly, they partly inherit any primordial parity violation of tensor modes. We find that chirality in primordial GWs can lead to distinguishing effects in scalar-tensor induced GWs in the ultraviolet (UV) region. We also address a potential divergence in our GWs and explore possible solutions. This study contributes to our understanding of GWs in the early Universe and their implications for cosmology and GWs detection. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2307.05404v2-abstract-full').style.display = 'none'; document.getElementById('2307.05404v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 1 June, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 11 July, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">35 pages, 7 figures, Published in Physical Review D</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2305.01602">arXiv:2305.01602</a> <span> [<a href="https://arxiv.org/pdf/2305.01602">pdf</a>, <a href="https://arxiv.org/format/2305.01602">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> </div> </div> <p class="title is-5 mathjax"> GW_CLASS: Cosmological Gravitational Wave Background in the Cosmic Linear Anisotropy Solving System </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Schulze%2C+F">Florian Schulze</a>, <a href="/search/gr-qc?searchtype=author&query=Dall%27Armi%2C+L+V">Lorenzo Valbusa Dall'Armi</a>, <a href="/search/gr-qc?searchtype=author&query=Lesgourgues%2C+J">Julien Lesgourgues</a>, <a href="/search/gr-qc?searchtype=author&query=Ricciardone%2C+A">Angelo Ricciardone</a>, <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">Nicola Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Bertacca%2C+D">Daniele Bertacca</a>, <a href="/search/gr-qc?searchtype=author&query=Fidler%2C+C">Christian Fidler</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2305.01602v2-abstract-short" style="display: inline;"> The anisotropies of the Cosmological Gravitational Wave Background (CGWB) retain information about the primordial mechanisms that source the gravitational waves and about the geometry and the particle content of the universe at early times. In this work, we discuss in detail the computation of the angular power spectra of CGWB anisotropies and of their cross correlation with Cosmic Microwave Backg… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2305.01602v2-abstract-full').style.display = 'inline'; document.getElementById('2305.01602v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2305.01602v2-abstract-full" style="display: none;"> The anisotropies of the Cosmological Gravitational Wave Background (CGWB) retain information about the primordial mechanisms that source the gravitational waves and about the geometry and the particle content of the universe at early times. In this work, we discuss in detail the computation of the angular power spectra of CGWB anisotropies and of their cross correlation with Cosmic Microwave Background (CMB) anisotropies, assuming different processes for the generation of these primordial signals. We present an efficient implementation of our results in a modified version of CLASS which will be publicly available. By combining our new code GW_CLASS with MontePython, we forecast the combined sensitivity of future gravitational wave interferometers and CMB experiments to the cosmological parameters that characterize the cosmological gravitational wave background. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2305.01602v2-abstract-full').style.display = 'none'; document.getElementById('2305.01602v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 11 September, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 2 May, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">64 pages, 16 figures. V2 matches the version published by JCAP. GW_CLASS is publicly available on the class_public git repository as a branch GW_CLASS, https://github.com/lesgourg/class_public/tree/GW_CLASS (For details on installation and usage, follow the instructions in the README.)</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> ET-0151A-23, TTK-23-30 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2301.08205">arXiv:2301.08205</a> <span> [<a href="https://arxiv.org/pdf/2301.08205">pdf</a>, <a href="https://arxiv.org/format/2301.08205">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevLett.131.041401">10.1103/PhysRevLett.131.041401 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Circular Polarization of the Astrophysical Gravitational Wave Background </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Dall%27Armi%2C+L+V">Lorenzo Valbusa Dall'Armi</a>, <a href="/search/gr-qc?searchtype=author&query=Nishizawa%2C+A">Atsushi Nishizawa</a>, <a href="/search/gr-qc?searchtype=author&query=Ricciardone%2C+A">Angelo Ricciardone</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2301.08205v2-abstract-short" style="display: inline;"> The circular polarization of gravitational waves is a powerful observable to test parity violation in gravity and to distinguish between the primordial or the astrophysical origin of the stochastic background. This property comes from the expected unpolarized nature of the homogeneous and isotropic astrophysical background, contrary to some specific cosmological sources that can produce a polarize… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.08205v2-abstract-full').style.display = 'inline'; document.getElementById('2301.08205v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2301.08205v2-abstract-full" style="display: none;"> The circular polarization of gravitational waves is a powerful observable to test parity violation in gravity and to distinguish between the primordial or the astrophysical origin of the stochastic background. This property comes from the expected unpolarized nature of the homogeneous and isotropic astrophysical background, contrary to some specific cosmological sources that can produce a polarized background. However, in this work we show that there is a non-negligible amount of circular polarization also in the astrophysical background, generated by Poisson fluctuations in the number of unresolved sources, which can be detected by the third-generation interferometers with signal-to-noise ratio larger than one. We also explain in which cases the gravitational wave maps can be cleaned from this extra source of noise, exploiting the frequency and the angular dependence, in order to search for signals from the early Universe. Future studies about the detection of polarized cosmological backgrounds with ground- and space-based interferometers should account for the presence of such a foreground contribution. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.08205v2-abstract-full').style.display = 'none'; document.getElementById('2301.08205v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 10 July, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 19 January, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">10 pages, 1 figure. V2 matches the version accepted by PRL for publication</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2210.14934">arXiv:2210.14934</a> <span> [<a href="https://arxiv.org/pdf/2210.14934">pdf</a>, <a href="https://arxiv.org/format/2210.14934">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2022/12/016">10.1088/1475-7516/2022/12/016 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The effect of outflows on CMB bounds from Primordial Black Hole accretion </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Piga%2C+L">Lorenzo Piga</a>, <a href="/search/gr-qc?searchtype=author&query=Lucca%2C+M">Matteo Lucca</a>, <a href="/search/gr-qc?searchtype=author&query=Bellomo%2C+N">Nicola Bellomo</a>, <a href="/search/gr-qc?searchtype=author&query=Bosch-Ramon%2C+V">Valent矛 Bosch-Ramon</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Raccanelli%2C+A">Alvise Raccanelli</a>, <a href="/search/gr-qc?searchtype=author&query=Verde%2C+L">Licia Verde</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2210.14934v1-abstract-short" style="display: inline;"> Should Primordial Black Holes (PBHs) exist in nature, they would inevitably accrete baryonic matter in their vicinity. In turn, the consequent emission of high-energy radiation could affect the thermal history of the universe to an extent that can be probed with a number of cosmological observables such as the Cosmic Microwave Background (CMB) anisotropies. However, our understanding of the accret… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.14934v1-abstract-full').style.display = 'inline'; document.getElementById('2210.14934v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2210.14934v1-abstract-full" style="display: none;"> Should Primordial Black Holes (PBHs) exist in nature, they would inevitably accrete baryonic matter in their vicinity. In turn, the consequent emission of high-energy radiation could affect the thermal history of the universe to an extent that can be probed with a number of cosmological observables such as the Cosmic Microwave Background (CMB) anisotropies. However, our understanding of the accretion and radiation emission processes in the context of PBHs is still in its infancy, and very large theoretical uncertainties affect the resulting constraints on the PBH abundance. Building on state-of-the-art literature, in this work we take a step towards the development of a more realistic picture of PBH accretion by accounting for the contribution of outflows. Specifically, we derive CMB-driven constraints on the PBH abundance for various accretion geometries, ionization models and mass distributions in absence and in presence of mechanical feedback and non-thermal emissions due to the outflows. As a result, we show that the presence of such outflows introduces an additional layer of uncertainty that needs to be taken into account when quoting cosmological constraints on the PBH abundance, with important consequences in particular in the LIGO-Virgo-KAGRA observational window. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.14934v1-abstract-full').style.display = 'none'; document.getElementById('2210.14934v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 October, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">34 pages, 8 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> ULB-TH/22-14, UTWI-11-2022 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2210.10102">arXiv:2210.10102</a> <span> [<a href="https://arxiv.org/pdf/2210.10102">pdf</a>, <a href="https://arxiv.org/ps/2210.10102">ps</a>, <a href="https://arxiv.org/format/2210.10102">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> </div> <p class="title is-5 mathjax"> Why is zero spatial curvature special? </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Jimenez%2C+R">Raul Jimenez</a>, <a href="/search/gr-qc?searchtype=author&query=Khalife%2C+A+R">Ali Rida Khalife</a>, <a href="/search/gr-qc?searchtype=author&query=Litim%2C+D+F">Daniel F. Litim</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Wandelt%2C+B+D">Benjamin D. Wandelt</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2210.10102v2-abstract-short" style="display: inline;"> Evidence for almost spatial flatness of the Universe has been provided from several observational probes, including the Cosmic Microwave Background (CMB) and Baryon Acoustic Oscillations (BAO) from galaxy clustering data. However, other than inflation, and in this case only in the limit of infinite time, there is no strong a priori motivation for a spatially flat Universe. Using the renormalizatio… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.10102v2-abstract-full').style.display = 'inline'; document.getElementById('2210.10102v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2210.10102v2-abstract-full" style="display: none;"> Evidence for almost spatial flatness of the Universe has been provided from several observational probes, including the Cosmic Microwave Background (CMB) and Baryon Acoustic Oscillations (BAO) from galaxy clustering data. However, other than inflation, and in this case only in the limit of infinite time, there is no strong a priori motivation for a spatially flat Universe. Using the renormalization group (RG) technique in curved spacetime, we present in this work a theoretical motivation for spatial flatness. Starting from a general spacetime, the first step of the RG, coarse-graining, gives a Friedmann-Lema卯tre-Robertson-Walker (FLRW) metric with a set of parameters. Then, we study the rescaling properties of the curvature parameter, and find that zero spatial curvature of the FLRW metric is singled out as the unique scale-free, non-singular background for cosmological perturbations. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.10102v2-abstract-full').style.display = 'none'; document.getElementById('2210.10102v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 September, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 18 October, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Matches accepted version to JCAP; minor changes; conclusions unchanged</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> JCAP09(2023)007 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2209.05329">arXiv:2209.05329</a> <span> [<a href="https://arxiv.org/pdf/2209.05329">pdf</a>, <a href="https://arxiv.org/format/2209.05329">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2023/07/034">10.1088/1475-7516/2023/07/034 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> An Analytical Study of the Primordial Gravitational-Wave-Induced Contribution to the Large-Scale Structure of the Universe </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Bari%2C+P">Pritha Bari</a>, <a href="/search/gr-qc?searchtype=author&query=Bertacca%2C+D">Daniele Bertacca</a>, <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">Nicola Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Ricciardone%2C+A">Angelo Ricciardone</a>, <a href="/search/gr-qc?searchtype=author&query=Giardiello%2C+S">Serena Giardiello</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2209.05329v2-abstract-short" style="display: inline;"> The imprint of gravitational waves (GWs) on large-scale structures (LSS) is a useful and promising way to detect or to constrain them. Tensor fossils have been largely studied in the literature as an indirect way to detect primordial GWs. In this paper we analyze a new effect induced by primordial GWs: a correction to the density contrast of the underlying matter distribution of LSS, as well as it… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.05329v2-abstract-full').style.display = 'inline'; document.getElementById('2209.05329v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2209.05329v2-abstract-full" style="display: none;"> The imprint of gravitational waves (GWs) on large-scale structures (LSS) is a useful and promising way to detect or to constrain them. Tensor fossils have been largely studied in the literature as an indirect way to detect primordial GWs. In this paper we analyze a new effect induced by primordial GWs: a correction to the density contrast of the underlying matter distribution of LSS, as well as its radiation counterpart, induced by the energy density fluctuation of the gravitational radiation. We perform our derivation of the full analytical solution of the density contrast for waves entering the horizon during radiation dominance. We account for two phases in the radiation era, depending on the main contributor to the perturbed energy density of the Universe. By comparing the density contrast of cold dark matter and radiation -- sourced by linear gravitational waves only -- we conclude that the former overcomes the latter at some time in the radiation era, a behaviour analogous to their linear counterpart. Then we conclude by discussing the case of density perturbations produced by GWs entering the Hubble radius during the matter era as well as their evolution in the late dark-energy dominated phase. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.05329v2-abstract-full').style.display = 'none'; document.getElementById('2209.05329v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 3 July, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 12 September, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">50 pages, 1 figure, version accepted for publication in JCAP</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2208.00075">arXiv:2208.00075</a> <span> [<a href="https://arxiv.org/pdf/2208.00075">pdf</a>, <a href="https://arxiv.org/format/2208.00075">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2022/11/034">10.1088/1475-7516/2022/11/034 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Physical Content of Long Tensor Modes in Cosmology </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">Nicola Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Carollo%2C+G+B">Giovanni Battista Carollo</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Pilo%2C+L">Luigi Pilo</a>, <a href="/search/gr-qc?searchtype=author&query=Rollo%2C+R">Rocco Rollo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2208.00075v1-abstract-short" style="display: inline;"> We analyze the physical content of squeezed bispectra involving long-wavelength tensor perturbations, showing that these modes cannot be gauged away, except for the exact (unphysical) limit of infinite wavelength, $k = 0$. This result has a direct implication on the validity of the Maldacena consistency relation, respected by a subclass of inflationary models. Consequently, in the squeezed limit,… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2208.00075v1-abstract-full').style.display = 'inline'; document.getElementById('2208.00075v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2208.00075v1-abstract-full" style="display: none;"> We analyze the physical content of squeezed bispectra involving long-wavelength tensor perturbations, showing that these modes cannot be gauged away, except for the exact (unphysical) limit of infinite wavelength, $k = 0$. This result has a direct implication on the validity of the Maldacena consistency relation, respected by a subclass of inflationary models. Consequently, in the squeezed limit, as in the case of the scalar-scalar-scalar bispectrum, squeezed mixed correlators could be observed by future experiments, remaining a key channel to study Early Universe physics and discriminate among different models of inflation. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2208.00075v1-abstract-full').style.display = 'none'; document.getElementById('2208.00075v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 29 July, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">13 pages</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> JCAP11(2022)034 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2205.01597">arXiv:2205.01597</a> <span> [<a href="https://arxiv.org/pdf/2205.01597">pdf</a>, <a href="https://arxiv.org/format/2205.01597">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1007/s41114-022-00036-9">10.1007/s41114-022-00036-9 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> New Horizons for Fundamental Physics with LISA </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Arun%2C+K+G">K. G. Arun</a>, <a href="/search/gr-qc?searchtype=author&query=Belgacem%2C+E">Enis Belgacem</a>, <a href="/search/gr-qc?searchtype=author&query=Benkel%2C+R">Robert Benkel</a>, <a href="/search/gr-qc?searchtype=author&query=Bernard%2C+L">Laura Bernard</a>, <a href="/search/gr-qc?searchtype=author&query=Berti%2C+E">Emanuele Berti</a>, <a href="/search/gr-qc?searchtype=author&query=Bertone%2C+G">Gianfranco Bertone</a>, <a href="/search/gr-qc?searchtype=author&query=Besancon%2C+M">Marc Besancon</a>, <a href="/search/gr-qc?searchtype=author&query=Blas%2C+D">Diego Blas</a>, <a href="/search/gr-qc?searchtype=author&query=B%C3%B6hmer%2C+C+G">Christian G. B枚hmer</a>, <a href="/search/gr-qc?searchtype=author&query=Brito%2C+R">Richard Brito</a>, <a href="/search/gr-qc?searchtype=author&query=Calcagni%2C+G">Gianluca Calcagni</a>, <a href="/search/gr-qc?searchtype=author&query=Cardenas-Avenda%C3%B1o%2C+A">Alejandro Cardenas-Avenda帽o</a>, <a href="/search/gr-qc?searchtype=author&query=Clough%2C+K">Katy Clough</a>, <a href="/search/gr-qc?searchtype=author&query=Crisostomi%2C+M">Marco Crisostomi</a>, <a href="/search/gr-qc?searchtype=author&query=De+Luca%2C+V">Valerio De Luca</a>, <a href="/search/gr-qc?searchtype=author&query=Doneva%2C+D">Daniela Doneva</a>, <a href="/search/gr-qc?searchtype=author&query=Escoffier%2C+S">Stephanie Escoffier</a>, <a href="/search/gr-qc?searchtype=author&query=Ezquiaga%2C+J+M">Jose Maria Ezquiaga</a>, <a href="/search/gr-qc?searchtype=author&query=Ferreira%2C+P+G">Pedro G. Ferreira</a>, <a href="/search/gr-qc?searchtype=author&query=Fleury%2C+P">Pierre Fleury</a>, <a href="/search/gr-qc?searchtype=author&query=Foffa%2C+S">Stefano Foffa</a>, <a href="/search/gr-qc?searchtype=author&query=Franciolini%2C+G">Gabriele Franciolini</a>, <a href="/search/gr-qc?searchtype=author&query=Frusciante%2C+N">Noemi Frusciante</a>, <a href="/search/gr-qc?searchtype=author&query=Garc%C3%ADa-Bellido%2C+J">Juan Garc铆a-Bellido</a>, <a href="/search/gr-qc?searchtype=author&query=Herdeiro%2C+C">Carlos Herdeiro</a> , et al. (116 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2205.01597v1-abstract-short" style="display: inline;"> The Laser Interferometer Space Antenna (LISA) has the potential to reveal wonders about the fundamental theory of nature at play in the extreme gravity regime, where the gravitational interaction is both strong and dynamical. In this white paper, the Fundamental Physics Working Group of the LISA Consortium summarizes the current topics in fundamental physics where LISA observations of GWs can be e… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.01597v1-abstract-full').style.display = 'inline'; document.getElementById('2205.01597v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2205.01597v1-abstract-full" style="display: none;"> The Laser Interferometer Space Antenna (LISA) has the potential to reveal wonders about the fundamental theory of nature at play in the extreme gravity regime, where the gravitational interaction is both strong and dynamical. In this white paper, the Fundamental Physics Working Group of the LISA Consortium summarizes the current topics in fundamental physics where LISA observations of GWs can be expected to provide key input. We provide the briefest of reviews to then delineate avenues for future research directions and to discuss connections between this working group, other working groups and the consortium work package teams. These connections must be developed for LISA to live up to its science potential in these areas. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.01597v1-abstract-full').style.display = 'none'; document.getElementById('2205.01597v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 3 May, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted in: Living Reviews in Relativity</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">MSC Class:</span> 83CXX </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2202.12858">arXiv:2202.12858</a> <span> [<a href="https://arxiv.org/pdf/2202.12858">pdf</a>, <a href="https://arxiv.org/format/2202.12858">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2022/09/046">10.1088/1475-7516/2022/09/046 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Test of the Statistical Isotropy of the Universe using Gravitational Waves </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Galloni%2C+G">Giacomo Galloni</a>, <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">Nicola Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Migliaccio%2C+M">Marina Migliaccio</a>, <a href="/search/gr-qc?searchtype=author&query=Ricciardone%2C+A">Angelo Ricciardone</a>, <a href="/search/gr-qc?searchtype=author&query=Vittorio%2C+N">Nicola Vittorio</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2202.12858v3-abstract-short" style="display: inline;"> Since WMAP and Planck some anomalous features appeared in the Cosmic Microwave Background (CMB) large-angle anisotropy, the so-called anomalies. One of these is the hemispherical power asymmetry, i.e. a difference in the average power on the two hemispheres centered around (l, b) = (221, -20), which shows a relatively high level of significance. Such an anomaly could be the signature of a departur… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2202.12858v3-abstract-full').style.display = 'inline'; document.getElementById('2202.12858v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2202.12858v3-abstract-full" style="display: none;"> Since WMAP and Planck some anomalous features appeared in the Cosmic Microwave Background (CMB) large-angle anisotropy, the so-called anomalies. One of these is the hemispherical power asymmetry, i.e. a difference in the average power on the two hemispheres centered around (l, b) = (221, -20), which shows a relatively high level of significance. Such an anomaly could be the signature of a departure from statistical isotropy on large scales. Here we investigate the physical origin of this anomaly using the Cosmological Gravitational Wave Background (CGWB) detectable by future GW detectors. Indeed, the CGWB offers a unique window to explore the early universe and we show that it can be used in combination with CMB data to shed light on the statistical isotropy of our universe. Specifically, we study the evolution of gravitons in the presence of a modulating field in the scalar gravitational potentials accounting for the hemispherical power asymmetry and we infer the amplitude of this modulating field through a minimal variance estimator exploiting both constrained and unconstrained realizations of the CGWB. We show that the addition of the CGWB will allow an improvement in the assessment of the physical origin of the CMB power asymmetry. Accounting for the expected performances of LISA and BBO, we also show that the latter is expected to be signal-dominated on large-scales, proving that the CGWB could be the keystone to assess the significance of this anomaly. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2202.12858v3-abstract-full').style.display = 'none'; document.getElementById('2202.12858v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 5 October, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 February, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Added discussions, corrected typos. Matches published version</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> JCAP09(2022)046 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2111.06794">arXiv:2111.06794</a> <span> [<a href="https://arxiv.org/pdf/2111.06794">pdf</a>, <a href="https://arxiv.org/format/2111.06794">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2022/05/008">10.1088/1475-7516/2022/05/008 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Cuscuton Inflation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">Nicola Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Ganz%2C+A">Alexander Ganz</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2111.06794v2-abstract-short" style="display: inline;"> We study the impact of (generalized) cuscuton models on standard single scalar field inflation. Generalized cuscuton models are characterized by spatial covariant gravity where a scalar degree of freedom is made non dynamical, and there are just two tensor degrees of freedom. The presence of the non-dynamical scalar field does not spoil inflation but instead the modifications are, in general, slow… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2111.06794v2-abstract-full').style.display = 'inline'; document.getElementById('2111.06794v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2111.06794v2-abstract-full" style="display: none;"> We study the impact of (generalized) cuscuton models on standard single scalar field inflation. Generalized cuscuton models are characterized by spatial covariant gravity where a scalar degree of freedom is made non dynamical, and there are just two tensor degrees of freedom. The presence of the non-dynamical scalar field does not spoil inflation but instead the modifications are, in general, slow-roll suppressed leading to almost scale-invariant power spectra. However, the extra free parameters, which can be tuned relatively independently, lead to a larger parameter range for observable quantities, such as the tensor-to-scalar ratio. For the (generalized) cuscuton model the non-Gaussianties of the curvature bispectrum are suppressed by the slow-roll parameters, and, therefore, outside the reach of current experiments. However, generalized cuscuton models can lead to a different shape for the bispectrum which might be constrained by future experiments. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2111.06794v2-abstract-full').style.display = 'none'; document.getElementById('2111.06794v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 9 May, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 12 November, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Revised argumentation for the horizon crossing. This is the accepted version of an article accepted for publication in Journal of Cosmology and Astroparticle Physics. Neither SISSA Medialab Srl nor IOP Publishing Ltd is responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at the DOI link below</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2110.15059">arXiv:2110.15059</a> <span> [<a href="https://arxiv.org/pdf/2110.15059">pdf</a>, <a href="https://arxiv.org/format/2110.15059">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2022/06/030">10.1088/1475-7516/2022/06/030 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> CLASS_GWB: robust modeling of the astrophysical gravitational wave background anisotropies </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Bellomo%2C+N">Nicola Bellomo</a>, <a href="/search/gr-qc?searchtype=author&query=Bertacca%2C+D">Daniele Bertacca</a>, <a href="/search/gr-qc?searchtype=author&query=Jenkins%2C+A+C">Alexander C. Jenkins</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Raccanelli%2C+A">Alvise Raccanelli</a>, <a href="/search/gr-qc?searchtype=author&query=Regimbau%2C+T">Tania Regimbau</a>, <a href="/search/gr-qc?searchtype=author&query=Ricciardone%2C+A">Angelo Ricciardone</a>, <a href="/search/gr-qc?searchtype=author&query=Sakellariadou%2C+M">Mairi Sakellariadou</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2110.15059v1-abstract-short" style="display: inline;"> Gravitational radiation offers a unique possibility to study the large-scale structure of the Universe, gravitational wave sources and propagation in a completely novel way. Given that gravitational wave maps contain a wealth of astrophysical and cosmological information, interpreting this signal requires a non-trivial multidisciplinary approach. In this work we present the complete computation of… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2110.15059v1-abstract-full').style.display = 'inline'; document.getElementById('2110.15059v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2110.15059v1-abstract-full" style="display: none;"> Gravitational radiation offers a unique possibility to study the large-scale structure of the Universe, gravitational wave sources and propagation in a completely novel way. Given that gravitational wave maps contain a wealth of astrophysical and cosmological information, interpreting this signal requires a non-trivial multidisciplinary approach. In this work we present the complete computation of the signal produced by compact object mergers accounting for a detailed modelling of the astrophysical sources and for cosmological perturbations. We develop the CLASS_GWB code, which allows for the computation of the anisotropies of the astrophysical gravitational wave background, accounting for source and detector properties, as well as effects of gravitational wave propagation. We apply our numerical tools to robustly compute the angular power spectrum of the anisotropies of the gravitational wave background generated by astrophysical sources in the LIGO-Virgo frequency band. The end-to-end theoretical framework we present can be easily applied to different sources and detectors in other frequency bands. Moreover, the same numerical tools can be used to compute the anisotropies of gravitational wave maps of the sky made using resolved events. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2110.15059v1-abstract-full').style.display = 'none'; document.getElementById('2110.15059v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 October, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">58 pages, 11 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> KCL-PH-TH-2021-70 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2110.09549">arXiv:2110.09549</a> <span> [<a href="https://arxiv.org/pdf/2110.09549">pdf</a>, <a href="https://arxiv.org/ps/2110.09549">ps</a>, <a href="https://arxiv.org/format/2110.09549">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.105.043503">10.1103/PhysRevD.105.043503 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Breaking the Single Clock Symmetry: measuring single-field inflation non-Gaussian features </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Bertacca%2C+D">Daniele Bertacca</a>, <a href="/search/gr-qc?searchtype=author&query=Jimenez%2C+R">Raul Jimenez</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Verde%2C+L">Licia Verde</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2110.09549v1-abstract-short" style="display: inline;"> The Universe is not just cold dark matter and dark energy, it also contains baryons, radiation and neutrinos. The presence of these components, beyond the pressure-less cold dark matter and the quasi-uniform dark energy ones, imply that the single clock assumption from inflation is no longer preserved. Here we quantify this effect and show that the single-clock symmetry is ensured only on scales w… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2110.09549v1-abstract-full').style.display = 'inline'; document.getElementById('2110.09549v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2110.09549v1-abstract-full" style="display: none;"> The Universe is not just cold dark matter and dark energy, it also contains baryons, radiation and neutrinos. The presence of these components, beyond the pressure-less cold dark matter and the quasi-uniform dark energy ones, imply that the single clock assumption from inflation is no longer preserved. Here we quantify this effect and show that the single-clock symmetry is ensured only on scales where baryonic effects, neutrinos effects, or sound speed are zero. These scales depend on the cosmic epoch and the Universe composition. Hence for all use and purposes of interpreting state-of-the-art and possibly forthcoming surveys, in the accessible scales, single clock symmetry cannot be said to be satisfied. Breaking the single-clock symmetry has key consequences for the study of non-Gaussian features generated by pure single-field inflation which arise from non-linearities in the metric yielding non-Gaussianities of the local type: the $n_{s}-1$ and the relativistic $-5/3$ term. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2110.09549v1-abstract-full').style.display = 'none'; document.getElementById('2110.09549v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 18 October, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2021. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2106.02591">arXiv:2106.02591</a> <span> [<a href="https://arxiv.org/pdf/2106.02591">pdf</a>, <a href="https://arxiv.org/format/2106.02591">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevLett.127.271301">10.1103/PhysRevLett.127.271301 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Cross-correlating Astrophysical and Cosmological Gravitational Wave Backgrounds with the Cosmic Microwave Background </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Ricciardone%2C+A">Angelo Ricciardone</a>, <a href="/search/gr-qc?searchtype=author&query=Dall%27Armi%2C+L+V">Lorenzo Valbusa Dall'Armi</a>, <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">Nicola Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Bertacca%2C+D">Daniele Bertacca</a>, <a href="/search/gr-qc?searchtype=author&query=Liguori%2C+M">Michele Liguori</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2106.02591v2-abstract-short" style="display: inline;"> General Relativity provides us with an extremely powerful tool to extract at the same time astrophysical and cosmological information from the Stochastic Gravitational Wave Backgrounds (SGWBs): the cross-correlation with other cosmological tracers, since their anisotropies share a common origin and the same perturbed geodesics. In this letter we explore the cross-correlation of the cosmological an… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.02591v2-abstract-full').style.display = 'inline'; document.getElementById('2106.02591v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2106.02591v2-abstract-full" style="display: none;"> General Relativity provides us with an extremely powerful tool to extract at the same time astrophysical and cosmological information from the Stochastic Gravitational Wave Backgrounds (SGWBs): the cross-correlation with other cosmological tracers, since their anisotropies share a common origin and the same perturbed geodesics. In this letter we explore the cross-correlation of the cosmological and astrophysical SGWBs with Cosmic Microwave Background (CMB) anisotropies, showing that future GW detectors, such as LISA or BBO, have the ability to measure such cross-correlation signals. We also present, as a new tool in this context, constrained realization maps of the SGWBs extracted from the high-resolution CMB {\it Planck} maps. This technique allows, in the low-noise regime, to faithfully reconstruct the expected SGWB map by starting from CMB measurements. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.02591v2-abstract-full').style.display = 'none'; document.getElementById('2106.02591v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 30 December, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 4 June, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">6 pages, 6 figures, 3 appendices. Minor changes to match the published Physical Review Letter version</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2105.04552">arXiv:2105.04552</a> <span> [<a href="https://arxiv.org/pdf/2105.04552">pdf</a>, <a href="https://arxiv.org/format/2105.04552">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.104.043508">10.1103/PhysRevD.104.043508 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Isolating non-linearities of light propagation in inhomogeneous cosmologies </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Grasso%2C+M">Michele Grasso</a>, <a href="/search/gr-qc?searchtype=author&query=Villa%2C+E">Eleonora Villa</a>, <a href="/search/gr-qc?searchtype=author&query=Korzy%C5%84ski%2C+M">Miko艂aj Korzy艅ski</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2105.04552v1-abstract-short" style="display: inline;"> A new formulation for light propagation in geometric optics by means of the Bi-local Geodesic Operators is considered. We develop the BiGONLight Mathematica package, uniquely designed to apply this framework to compute optical observables in Numerical Relativity. Our package can be used for light propagation on a wide range of scales and redshifts and accepts numerical as well as analytical input… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2105.04552v1-abstract-full').style.display = 'inline'; document.getElementById('2105.04552v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2105.04552v1-abstract-full" style="display: none;"> A new formulation for light propagation in geometric optics by means of the Bi-local Geodesic Operators is considered. We develop the BiGONLight Mathematica package, uniquely designed to apply this framework to compute optical observables in Numerical Relativity. Our package can be used for light propagation on a wide range of scales and redshifts and accepts numerical as well as analytical input for the spacetime metric. In this paper we focus on two cosmological observables, the redshift and the angular diameter distance, specializing our analysis to a wall universe modeled within the post-Newtonian approximation. With this choice and the input metric in analytical form, we are able to estimate non-linearities of light propagation by comparing and isolating the contributions coming from Newtonian and post-Newtonian approximations as opposed to linear perturbation theory. We also clarify the role of the dominant post-Newtonian contribution represented by the linear initial seed which, strictly speaking, is absent in the Newtonian treatment. We found that post-Newtonian non-linear corrections are below $1\%$, in agreement with previous results in the literature. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2105.04552v1-abstract-full').style.display = 'none'; document.getElementById('2105.04552v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 10 May, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">21 pages, 16 figures. For the BiGONLight package, see https://github.com/MicGrasso/bigonlight1.0</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 104, 043508 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2104.04836">arXiv:2104.04836</a> <span> [<a href="https://arxiv.org/pdf/2104.04836">pdf</a>, <a href="https://arxiv.org/ps/2104.04836">ps</a>, <a href="https://arxiv.org/format/2104.04836">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Phenomenology">hep-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.104.083508">10.1103/PhysRevD.104.083508 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Non-Markovian open quantum system approach to the early universe: I. Damping of gravitational waves by matter </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Zarei%2C+M">Moslem Zarei</a>, <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">Nicola Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Bertacca%2C+D">Daniele Bertacca</a>, <a href="/search/gr-qc?searchtype=author&query=Ricciardone%2C+A">Angelo Ricciardone</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2104.04836v2-abstract-short" style="display: inline;"> By revising the application of the open quantum system approach to the early universe and extending it to the conditions beyond the Markovian approximation, we obtain a new non-Markovian quantum Boltzmann equation. Throughout the paper, we also develop an extension of the quantum Boltzmann equation to describe the processes that are irreversible at the macroscopic level. This new kinetic equation… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2104.04836v2-abstract-full').style.display = 'inline'; document.getElementById('2104.04836v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2104.04836v2-abstract-full" style="display: none;"> By revising the application of the open quantum system approach to the early universe and extending it to the conditions beyond the Markovian approximation, we obtain a new non-Markovian quantum Boltzmann equation. Throughout the paper, we also develop an extension of the quantum Boltzmann equation to describe the processes that are irreversible at the macroscopic level. This new kinetic equation is, in principle, applicable to a wide variety of processes in the early universe. For instance, using this equation one can accurately study the microscopic influence of a cosmic environment on a system of cosmic background photons or stochastic gravitational waves. In this paper, we apply the non-Markovian quantum Boltzmann equation to study the damping of gravitational waves propagating in a medium consisting of decoupled ultra-relativistic neutrinos. For such a system, we study the time evolution of the intensity and the polarization of the gravitational waves. It is shown that, in contrast to intensity and linear polarization which are damped, the circular polarization (V-mode) of the gravitational wave (if present) is amplified by propagating through such a medium. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2104.04836v2-abstract-full').style.display = 'none'; document.getElementById('2104.04836v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 20 September, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 10 April, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Final published version. 40 pages, 2 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 104, 083508 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2103.00155">arXiv:2103.00155</a> <span> [<a href="https://arxiv.org/pdf/2103.00155">pdf</a>, <a href="https://arxiv.org/format/2103.00155">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2021/06/050">10.1088/1475-7516/2021/06/050 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Gravitational-wave cosmological distances in scalar-tensor theories of gravity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Tasinato%2C+G">Gianmassimo Tasinato</a>, <a href="/search/gr-qc?searchtype=author&query=Garoffolo%2C+A">Alice Garoffolo</a>, <a href="/search/gr-qc?searchtype=author&query=Bertacca%2C+D">Daniele Bertacca</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2103.00155v2-abstract-short" style="display: inline;"> We analyze the propagation of high-frequency gravitational waves (GW) in scalar-tensor theories of gravity, with the aim of examining properties of cosmological distances as inferred from GW measurements. By using symmetry principles, we first determine the most general structure of the GW linearized equations and of the GW energy momentum tensor, assuming that GW move with the speed of light. Mod… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.00155v2-abstract-full').style.display = 'inline'; document.getElementById('2103.00155v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2103.00155v2-abstract-full" style="display: none;"> We analyze the propagation of high-frequency gravitational waves (GW) in scalar-tensor theories of gravity, with the aim of examining properties of cosmological distances as inferred from GW measurements. By using symmetry principles, we first determine the most general structure of the GW linearized equations and of the GW energy momentum tensor, assuming that GW move with the speed of light. Modified gravity effects are encoded in a small number of parameters, and we study the conditions for ensuring graviton number conservation in our covariant set-up. We then apply our general findings to the case of GW propagating through a perturbed cosmological space-time, deriving the expressions for the GW luminosity distance $d_L^{({\rm GW})}$ and the GW angular distance $d_A^{({\rm GW})}$. We prove for the first time the validity of Etherington reciprocity law $d_L^{({\rm GW})}\,=\,(1+z)^2\,d_A^{({\rm GW})}$ for a perturbed universe within a scalar-tensor framework. We find that besides the GW luminosity distance, also the GW angular distance can be modified with respect to General Relativity. We discuss implications of this result for gravitational lensing, focussing on time-delays of lensed GW and lensed photons emitted simultaneously during a multimessenger event. We explicitly show how modified gravity effects compensate between different coefficients in the GW time-delay formula: lensed GW arrive at the same time as their lensed electromagnetic counterparts, in agreement with causality constraints. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.00155v2-abstract-full').style.display = 'none'; document.getElementById('2103.00155v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 28 June, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 27 February, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">22 pages plus technical appendixes. 3 figures. V2: version published in JCAP</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2007.13722">arXiv:2007.13722</a> <span> [<a href="https://arxiv.org/pdf/2007.13722">pdf</a>, <a href="https://arxiv.org/format/2007.13722">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.103.083506">10.1103/PhysRevD.103.083506 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Detecting Dark Energy Fluctuations with Gravitational Waves </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Garoffolo%2C+A">Alice Garoffolo</a>, <a href="/search/gr-qc?searchtype=author&query=Raveri%2C+M">Marco Raveri</a>, <a href="/search/gr-qc?searchtype=author&query=Silvestri%2C+A">Alessandra Silvestri</a>, <a href="/search/gr-qc?searchtype=author&query=Tasinato%2C+G">Gianmassimo Tasinato</a>, <a href="/search/gr-qc?searchtype=author&query=Carbone%2C+C">Carmelita Carbone</a>, <a href="/search/gr-qc?searchtype=author&query=Bertacca%2C+D">Daniele Bertacca</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2007.13722v2-abstract-short" style="display: inline;"> Luminosity distance estimates from electromagnetic and gravitational wave sources are generally different in models of dynamical dark energy and gravity beyond the standard cosmological scenario. We show that this leaves a unique imprint on the angular power-spectrum of fluctuations of the luminosity distance of gravitational-wave observations which tracks inhomogeneities in the dark energy field.… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.13722v2-abstract-full').style.display = 'inline'; document.getElementById('2007.13722v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2007.13722v2-abstract-full" style="display: none;"> Luminosity distance estimates from electromagnetic and gravitational wave sources are generally different in models of dynamical dark energy and gravity beyond the standard cosmological scenario. We show that this leaves a unique imprint on the angular power-spectrum of fluctuations of the luminosity distance of gravitational-wave observations which tracks inhomogeneities in the dark energy field. Exploiting the synergy in supernovae and gravitational wave distance measurements, we build a joint estimator that directly probes dark energy fluctuations, providing a conclusive evidence for their existence in case of detection. Moreover, such measurement would also allow to probe the running of the Planck mass. We discuss experimental requirements to detect these signals. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.13722v2-abstract-full').style.display = 'none'; document.getElementById('2007.13722v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 3 May, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 27 July, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">9 pages, 2 figures. Matching published version</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 103, 083506 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2007.01215">arXiv:2007.01215</a> <span> [<a href="https://arxiv.org/pdf/2007.01215">pdf</a>, <a href="https://arxiv.org/format/2007.01215">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Phenomenology">hep-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.103.023522">10.1103/PhysRevD.103.023522 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Imprint of Relativistic Particles on the Anisotropies of the Stochastic Gravitational-Wave Background </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Dall%27Armi%2C+L+V">Lorenzo Valbusa Dall'Armi</a>, <a href="/search/gr-qc?searchtype=author&query=Ricciardone%2C+A">Angelo Ricciardone</a>, <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">Nicola Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Bertacca%2C+D">Daniele Bertacca</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2007.01215v1-abstract-short" style="display: inline;"> The Stochastic Gravitational-Wave Background (SGWB) is expected to be a key observable for Gravitational-Wave (GW) interferometry. Its detection will open a new window on early Universe cosmology, on the astrophysics of compact objects and, as shown in this Letter, on the particle physics content of the Universe. In this Letter we show that, besides their effects on the Cosmic Microwave Background… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.01215v1-abstract-full').style.display = 'inline'; document.getElementById('2007.01215v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2007.01215v1-abstract-full" style="display: none;"> The Stochastic Gravitational-Wave Background (SGWB) is expected to be a key observable for Gravitational-Wave (GW) interferometry. Its detection will open a new window on early Universe cosmology, on the astrophysics of compact objects and, as shown in this Letter, on the particle physics content of the Universe. In this Letter we show that, besides their effects on the Cosmic Microwave Background (CMB) and on Large Scale Structure (LSS), relativistic particles in the early Universe leave a clear imprint on the anisotropies of the SGWB. In particular we show that a change in the number of decoupled relativistic particles shifts the angular power spectrum of the SGWB, as both the Sachs-Wolfe (SW) and the Integrated Sachs-Wolfe (ISW) terms are affected. Being very large-angle effects, these lead to new testable predictions for future GW interferometers. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.01215v1-abstract-full').style.display = 'none'; document.getElementById('2007.01215v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 2 July, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">5 pages, 3 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 103, 023522 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2006.14418">arXiv:2006.14418</a> <span> [<a href="https://arxiv.org/pdf/2006.14418">pdf</a>, <a href="https://arxiv.org/ps/2006.14418">ps</a>, <a href="https://arxiv.org/format/2006.14418">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Phenomenology">hep-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.102.063501">10.1103/PhysRevD.102.063501 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> CMB $V$ modes from photon-photon forward scattering revisited </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Hoseinpour%2C+A">Ahmad Hoseinpour</a>, <a href="/search/gr-qc?searchtype=author&query=Zarei%2C+M">Moslem Zarei</a>, <a href="/search/gr-qc?searchtype=author&query=Orlando%2C+G">Giorgio Orlando</a>, <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">Nicola Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2006.14418v2-abstract-short" style="display: inline;"> Recent literature has shown that photon-photon forward scattering mediated by Euler-Heisenberg interactions may generate some amount of the circular polarization ($V$ modes) in the cosmic microwave background (CMB) photons. However, there is an apparent contradiction among the different references about the predicted level of the amplitude of this circular polarization. In this work, we will resol… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2006.14418v2-abstract-full').style.display = 'inline'; document.getElementById('2006.14418v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2006.14418v2-abstract-full" style="display: none;"> Recent literature has shown that photon-photon forward scattering mediated by Euler-Heisenberg interactions may generate some amount of the circular polarization ($V$ modes) in the cosmic microwave background (CMB) photons. However, there is an apparent contradiction among the different references about the predicted level of the amplitude of this circular polarization. In this work, we will resolve this discrepancy by showing that with a quantum Boltzmann equation formalism we obtain the same amount of circular polarization as using a geometrical approach that is based on the index of refraction of the cosmological medium. We will show that the expected amplitude of $V$ modes is expected to be $\approx$ 8 orders of magnitude smaller than the amplitude of $E$-polarization modes that we actually observe in the CMB, thus confirming that it is going to be challenging to observe such a signature. Throughout the paper, we also develop a general method to study the generation of $V$ modes from photon-photon and photon-spin-1-massive-particle forward scatterings without relying on a specific interaction, which thus represent possible new signatures of physics beyond the Standard Model. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2006.14418v2-abstract-full').style.display = 'none'; document.getElementById('2006.14418v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 2 September, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 June, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">22 pages, 2 figures; v2: minor corrections implemented in the text. Replaced to match published version in PRD</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 102, 063501 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2001.09793">arXiv:2001.09793</a> <span> [<a href="https://arxiv.org/pdf/2001.09793">pdf</a>, <a href="https://arxiv.org/ps/2001.09793">ps</a>, <a href="https://arxiv.org/format/2001.09793">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1007/s10714-020-02691-1">10.1007/s10714-020-02691-1 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Prospects for Fundamental Physics with LISA </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Barausse%2C+E">Enrico Barausse</a>, <a href="/search/gr-qc?searchtype=author&query=Berti%2C+E">Emanuele Berti</a>, <a href="/search/gr-qc?searchtype=author&query=Hertog%2C+T">Thomas Hertog</a>, <a href="/search/gr-qc?searchtype=author&query=Hughes%2C+S+A">Scott A. Hughes</a>, <a href="/search/gr-qc?searchtype=author&query=Jetzer%2C+P">Philippe Jetzer</a>, <a href="/search/gr-qc?searchtype=author&query=Pani%2C+P">Paolo Pani</a>, <a href="/search/gr-qc?searchtype=author&query=Sotiriou%2C+T+P">Thomas P. Sotiriou</a>, <a href="/search/gr-qc?searchtype=author&query=Tamanini%2C+N">Nicola Tamanini</a>, <a href="/search/gr-qc?searchtype=author&query=Witek%2C+H">Helvi Witek</a>, <a href="/search/gr-qc?searchtype=author&query=Yagi%2C+K">Kent Yagi</a>, <a href="/search/gr-qc?searchtype=author&query=Yunes%2C+N">Nicolas Yunes</a>, <a href="/search/gr-qc?searchtype=author&query=Abdelsalhin%2C+T">T. Abdelsalhin</a>, <a href="/search/gr-qc?searchtype=author&query=Achucarro%2C+A">A. Achucarro</a>, <a href="/search/gr-qc?searchtype=author&query=Aelst%2C+K+V">K. V. Aelst</a>, <a href="/search/gr-qc?searchtype=author&query=Afshordi%2C+N">N. Afshordi</a>, <a href="/search/gr-qc?searchtype=author&query=Akcay%2C+S">S. Akcay</a>, <a href="/search/gr-qc?searchtype=author&query=Annulli%2C+L">L. Annulli</a>, <a href="/search/gr-qc?searchtype=author&query=Arun%2C+K+G">K. G. Arun</a>, <a href="/search/gr-qc?searchtype=author&query=Ayuso%2C+I">I. Ayuso</a>, <a href="/search/gr-qc?searchtype=author&query=Baibhav%2C+V">V. Baibhav</a>, <a href="/search/gr-qc?searchtype=author&query=Baker%2C+T">T. Baker</a>, <a href="/search/gr-qc?searchtype=author&query=Bantilan%2C+H">H. Bantilan</a>, <a href="/search/gr-qc?searchtype=author&query=Barreiro%2C+T">T. Barreiro</a>, <a href="/search/gr-qc?searchtype=author&query=Barrera-Hinojosa%2C+C">C. Barrera-Hinojosa</a>, <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">N. Bartolo</a> , et al. (296 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2001.09793v3-abstract-short" style="display: inline;"> In this paper, which is of programmatic rather than quantitative nature, we aim to further delineate and sharpen the future potential of the LISA mission in the area of fundamental physics. Given the very broad range of topics that might be relevant to LISA, we present here a sample of what we view as particularly promising directions, based in part on the current research interests of the LISA sc… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2001.09793v3-abstract-full').style.display = 'inline'; document.getElementById('2001.09793v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2001.09793v3-abstract-full" style="display: none;"> In this paper, which is of programmatic rather than quantitative nature, we aim to further delineate and sharpen the future potential of the LISA mission in the area of fundamental physics. Given the very broad range of topics that might be relevant to LISA, we present here a sample of what we view as particularly promising directions, based in part on the current research interests of the LISA scientific community in the area of fundamental physics. We organize these directions through a "science-first" approach that allows us to classify how LISA data can inform theoretical physics in a variety of areas. For each of these theoretical physics classes, we identify the sources that are currently expected to provide the principal contribution to our knowledge, and the areas that need further development. The classification presented here should not be thought of as cast in stone, but rather as a fluid framework that is amenable to change with the flow of new insights in theoretical physics. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2001.09793v3-abstract-full').style.display = 'none'; document.getElementById('2001.09793v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 27 April, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 27 January, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">22 pages, 1 figure, to appear in General Relativity and Gravitation</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Gen.Rel.Grav. 52 (2020) 8, 81 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1912.08093">arXiv:1912.08093</a> <span> [<a href="https://arxiv.org/pdf/1912.08093">pdf</a>, <a href="https://arxiv.org/ps/1912.08093">ps</a>, <a href="https://arxiv.org/format/1912.08093">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2020/11/040">10.1088/1475-7516/2020/11/040 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Gravitational waves and geometrical optics in scalar-tensor theories </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Garoffolo%2C+A">Alice Garoffolo</a>, <a href="/search/gr-qc?searchtype=author&query=Tasinato%2C+G">Gianmassimo Tasinato</a>, <a href="/search/gr-qc?searchtype=author&query=Carbone%2C+C">Carmelita Carbone</a>, <a href="/search/gr-qc?searchtype=author&query=Bertacca%2C+D">Daniele Bertacca</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1912.08093v3-abstract-short" style="display: inline;"> The detection of gravitational waves (GWs) propagating through cosmic structures can provide invaluable information on the geometry and content of our Universe, as well as on the fundamental theory of gravity. In order to test possible departures from General Relativity, it is essential to analyse, in a modified gravity setting, how GWs propagate through a perturbed cosmological space-time. Workin… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1912.08093v3-abstract-full').style.display = 'inline'; document.getElementById('1912.08093v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1912.08093v3-abstract-full" style="display: none;"> The detection of gravitational waves (GWs) propagating through cosmic structures can provide invaluable information on the geometry and content of our Universe, as well as on the fundamental theory of gravity. In order to test possible departures from General Relativity, it is essential to analyse, in a modified gravity setting, how GWs propagate through a perturbed cosmological space-time. Working within the framework of geometrical optics, we develop tools to address this topic for a broad class of scalar-tensor theories, including scenarios with non-minimal, derivative couplings between scalar and tensor modes. We determine the corresponding evolution equations for the GW amplitude and polarization tensor. The former satisfies a generalised evolution equation that includes possible effects due to a variation of the effective Planck scale; the latter can fail to be parallely transported along GW geodesics unless certain conditions are satisfied. We apply our general formulas to specific scalar-tensor theories with unit tensor speed, and then focus on GW propagation on a perturbed space-time. We determine corrections to standard formulas for the GW luminosity distance and for the evolution of the polarization tensor, which depend both on modified gravity and on the effects of cosmological perturbations. Our results can constitute a starting point to disentangle among degeneracies from different sectors that can influence GW propagation through cosmological space-times. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1912.08093v3-abstract-full').style.display = 'none'; document.getElementById('1912.08093v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 28 September, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 16 December, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">42 pages. V2: Improved discussion, in particular on gauge conditions, and references added. Results unchanged. V3: Updated version to be published in JCAP</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1912.02622">arXiv:1912.02622</a> <span> [<a href="https://arxiv.org/pdf/1912.02622">pdf</a>, <a href="https://arxiv.org/format/1912.02622">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2020/03/050">10.1088/1475-7516/2020/03/050 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Science Case for the Einstein Telescope </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Maggiore%2C+M">Michele Maggiore</a>, <a href="/search/gr-qc?searchtype=author&query=Broeck%2C+C+v+d">Chris van den Broeck</a>, <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">Nicola Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Belgacem%2C+E">Enis Belgacem</a>, <a href="/search/gr-qc?searchtype=author&query=Bertacca%2C+D">Daniele Bertacca</a>, <a href="/search/gr-qc?searchtype=author&query=Bizouard%2C+M+A">Marie Anne Bizouard</a>, <a href="/search/gr-qc?searchtype=author&query=Branchesi%2C+M">Marica Branchesi</a>, <a href="/search/gr-qc?searchtype=author&query=Clesse%2C+S">Sebastien Clesse</a>, <a href="/search/gr-qc?searchtype=author&query=Foffa%2C+S">Stefano Foffa</a>, <a href="/search/gr-qc?searchtype=author&query=Garc%C3%ADa-Bellido%2C+J">Juan Garc铆a-Bellido</a>, <a href="/search/gr-qc?searchtype=author&query=Grimm%2C+S">Stefan Grimm</a>, <a href="/search/gr-qc?searchtype=author&query=Harms%2C+J">Jan Harms</a>, <a href="/search/gr-qc?searchtype=author&query=Hinderer%2C+T">Tanja Hinderer</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Palomba%2C+C">Cristiano Palomba</a>, <a href="/search/gr-qc?searchtype=author&query=Peloso%2C+M">Marco Peloso</a>, <a href="/search/gr-qc?searchtype=author&query=Ricciardone%2C+A">Angelo Ricciardone</a>, <a href="/search/gr-qc?searchtype=author&query=Sakellariadou%2C+M">Mairi Sakellariadou</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1912.02622v4-abstract-short" style="display: inline;"> The Einstein Telescope (ET), a proposed European ground-based gravitational-wave detector of third-generation, is an evolution of second-generation detectors such as Advanced LIGO, Advanced Virgo, and KAGRA which could be operating in the mid 2030s. ET will explore the universe with gravitational waves up to cosmological distances. We discuss its main scientific objectives and its potential for di… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1912.02622v4-abstract-full').style.display = 'inline'; document.getElementById('1912.02622v4-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1912.02622v4-abstract-full" style="display: none;"> The Einstein Telescope (ET), a proposed European ground-based gravitational-wave detector of third-generation, is an evolution of second-generation detectors such as Advanced LIGO, Advanced Virgo, and KAGRA which could be operating in the mid 2030s. ET will explore the universe with gravitational waves up to cosmological distances. We discuss its main scientific objectives and its potential for discoveries in astrophysics, cosmology and fundamental physics. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1912.02622v4-abstract-full').style.display = 'none'; document.getElementById('1912.02622v4-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 March, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 5 December, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">51 pages, 14 figures; v3: references added, various improvements. v4: minor changes. Version published in JCAP</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1909.12619">arXiv:1909.12619</a> <span> [<a href="https://arxiv.org/pdf/1909.12619">pdf</a>, <a href="https://arxiv.org/format/1909.12619">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Phenomenology">hep-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2020/02/028">10.1088/1475-7516/2020/02/028 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Gravitational Wave Anisotropies from Primordial Black Holes </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">N. Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Bertacca%2C+D">D. Bertacca</a>, <a href="/search/gr-qc?searchtype=author&query=De+Luca%2C+V">V. De Luca</a>, <a href="/search/gr-qc?searchtype=author&query=Franciolini%2C+G">G. Franciolini</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">S. Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Peloso%2C+M">M. Peloso</a>, <a href="/search/gr-qc?searchtype=author&query=Ricciardone%2C+A">A. Ricciardone</a>, <a href="/search/gr-qc?searchtype=author&query=Riotto%2C+A">A. Riotto</a>, <a href="/search/gr-qc?searchtype=author&query=Tasinato%2C+G">G. Tasinato</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1909.12619v2-abstract-short" style="display: inline;"> An observable stochastic background of gravitational waves is generated whenever primordial black holes are created in the early universe thanks to a small-scale enhancement of the curvature perturbation. We calculate the anisotropies and non-Gaussianity of such stochastic gravitational waves background which receive two contributions, the first at formation time and the second due to propagation… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1909.12619v2-abstract-full').style.display = 'inline'; document.getElementById('1909.12619v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1909.12619v2-abstract-full" style="display: none;"> An observable stochastic background of gravitational waves is generated whenever primordial black holes are created in the early universe thanks to a small-scale enhancement of the curvature perturbation. We calculate the anisotropies and non-Gaussianity of such stochastic gravitational waves background which receive two contributions, the first at formation time and the second due to propagation effects. The former contribution can be generated if the distribution of the curvature perturbation is characterized by a local and scale-invariant shape of non-Gaussianity. Under such an assumption, we conclude that a sizeable magnitude of anisotropy and non-Gaussianity in the gravitational waves would suggest that primordial black holes may not comply the totality of the dark matter. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1909.12619v2-abstract-full').style.display = 'none'; document.getElementById('1909.12619v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 9 March, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 27 September, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">20 pages, 5 figures, version accepted by JCAP</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1909.11627">arXiv:1909.11627</a> <span> [<a href="https://arxiv.org/pdf/1909.11627">pdf</a>, <a href="https://arxiv.org/format/1909.11627">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.101.103513">10.1103/PhysRevD.101.103513 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Projection effects on the observed angular spectrum of the astrophysical stochastic gravitational wave background </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Bertacca%2C+D">Daniele Bertacca</a>, <a href="/search/gr-qc?searchtype=author&query=Ricciardone%2C+A">Angelo Ricciardone</a>, <a href="/search/gr-qc?searchtype=author&query=Bellomo%2C+N">Nicola Bellomo</a>, <a href="/search/gr-qc?searchtype=author&query=Jenkins%2C+A+C">Alexander C. Jenkins</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Raccanelli%2C+A">Alvise Raccanelli</a>, <a href="/search/gr-qc?searchtype=author&query=Regimbau%2C+T">Tania Regimbau</a>, <a href="/search/gr-qc?searchtype=author&query=Sakellariadou%2C+M">Mairi Sakellariadou</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1909.11627v4-abstract-short" style="display: inline;"> The detection and characterization of the Stochastic Gravitational Wave Background (SGWB) is one of the main goals of Gravitational Wave (GW) experiments. The observed SGWB will be the combination of GWs from cosmological (as predicted by many models describing the physics of the early Universe) and astrophysical origins, which will arise from the superposition of GWs from unresolved sources whose… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1909.11627v4-abstract-full').style.display = 'inline'; document.getElementById('1909.11627v4-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1909.11627v4-abstract-full" style="display: none;"> The detection and characterization of the Stochastic Gravitational Wave Background (SGWB) is one of the main goals of Gravitational Wave (GW) experiments. The observed SGWB will be the combination of GWs from cosmological (as predicted by many models describing the physics of the early Universe) and astrophysical origins, which will arise from the superposition of GWs from unresolved sources whose signal is too faint to be detected. Therefore, it is important to have a proper modeling of the astrophysical SGWB (ASGWB) in order to disentangle the two signals; moreover, this will provide additional information on astrophysical properties of compact objects. Applying the Cosmic Rulers formalism, we compute the observed ASGWB angular power spectrum, hence using gauge invariant quantities, accounting for all effects intervening between the source and the observer. These are the so-called projection effects, which include Kaiser, Doppler and gravitational potentials effect. Our results show that these projection effects are the most important at the largest scales, and they contribute to up to tens of percent of the angular power spectrum amplitude, with the Kaiser term being the largest at all scales. While the exact impact of these results will depend on instrumental and astrophysical details, a precise theoretical modeling of the ASGWB will necessarily need to include all these projection effects. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1909.11627v4-abstract-full').style.display = 'none'; document.getElementById('1909.11627v4-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 1 August, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 September, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">19 pages, 1 figure. Typos corrected; Minor corrections. Version accepted by Physical Review D</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> CERN-TH-2019-153, KCL-PH-TH 2019-73 </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 101, 103513 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1908.00527">arXiv:1908.00527</a> <span> [<a href="https://arxiv.org/pdf/1908.00527">pdf</a>, <a href="https://arxiv.org/format/1908.00527">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Phenomenology">hep-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.100.121501">10.1103/PhysRevD.100.121501 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Anisotropies and non-Gaussianity of the Cosmological Gravitational Wave Background </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">N. Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Bertacca%2C+D">D. Bertacca</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">S. Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Peloso%2C+M">M. Peloso</a>, <a href="/search/gr-qc?searchtype=author&query=Ricciardone%2C+A">A. Ricciardone</a>, <a href="/search/gr-qc?searchtype=author&query=Riotto%2C+A">A. Riotto</a>, <a href="/search/gr-qc?searchtype=author&query=Tasinato%2C+G">G. Tasinato</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1908.00527v1-abstract-short" style="display: inline;"> The Stochastic Gravitational Wave Background (SGWB) is expected to be a key observable for Gravitational Wave (GW) interferometry. Its detection will open a new window on early universe cosmology and on the astrophysics of compact objects. Using a Boltzmann approach, we study the angular anisotropies of the GW energy density, which is an important tool to disentangle the different cosmological and… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1908.00527v1-abstract-full').style.display = 'inline'; document.getElementById('1908.00527v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1908.00527v1-abstract-full" style="display: none;"> The Stochastic Gravitational Wave Background (SGWB) is expected to be a key observable for Gravitational Wave (GW) interferometry. Its detection will open a new window on early universe cosmology and on the astrophysics of compact objects. Using a Boltzmann approach, we study the angular anisotropies of the GW energy density, which is an important tool to disentangle the different cosmological and astrophysical contributions to the SGWB. Anisotropies in the cosmological background are imprinted both at its production, and by GW propagation through the large-scale scalar and tensor perturbations of the universe. The first contribution is not present in the Cosmic Microwave Background (CMB) radiation (as the universe is not transparent to photons before recombination), causing an order one dependence of the anisotropies on frequency. Moreover, we provide a new method to characterize the cosmological SGWB through its possible deviation from a Gaussian statistics. In particular, the SGWB will become a new probe of the primordial non-Gaussianity of the large-scale cosmological perturbations. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1908.00527v1-abstract-full').style.display = 'none'; document.getElementById('1908.00527v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 1 August, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">5 pages, 1 figure</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 100, 121501 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1907.10301">arXiv:1907.10301</a> <span> [<a href="https://arxiv.org/pdf/1907.10301">pdf</a>, <a href="https://arxiv.org/ps/1907.10301">ps</a>, <a href="https://arxiv.org/format/1907.10301">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2019/12/037">10.1088/1475-7516/2019/12/037 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Towards a viable effective field theory of mimetic gravity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Ganz%2C+A">Alexander Ganz</a>, <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">Nicola Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1907.10301v1-abstract-short" style="display: inline;"> We discuss mimetic gravity theories with direct couplings between the curvature and higher derivatives of the scalar field, up to the quintic order, which were proposed to solve the instability problem for linear perturbations around the FLRW background for this kind of models. Restricting to homogeneous scalar field configurations in the action, we derive degeneracy conditions to obtain an effect… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1907.10301v1-abstract-full').style.display = 'inline'; document.getElementById('1907.10301v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1907.10301v1-abstract-full" style="display: none;"> We discuss mimetic gravity theories with direct couplings between the curvature and higher derivatives of the scalar field, up to the quintic order, which were proposed to solve the instability problem for linear perturbations around the FLRW background for this kind of models. Restricting to homogeneous scalar field configurations in the action, we derive degeneracy conditions to obtain an effective field theory with three degrees of freedom. However, performing the Hamiltonian analysis for a generic scalar field we show that there are in general four or more degrees of freedom. The discrepancy is resolved because, for a homogeneous scalar field profile, $\partial_i\varphi\approx 0$, the Dirac matrix becomes singular, resulting in further constraints, which reduces the number of degrees of freedom to three. Similarly, in linear perturbation theory the additional scalar degree of freedom can only be seen by considering a non-homogeneous background profile of the scalar field. Therefore, restricting to homogeneous scalar fields these kinds of models provide viable explicitly Lorentz violating effective field theories of mimetic gravity. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1907.10301v1-abstract-full').style.display = 'none'; document.getElementById('1907.10301v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 July, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2019. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1906.01593">arXiv:1906.01593</a> <span> [<a href="https://arxiv.org/pdf/1906.01593">pdf</a>, <a href="https://arxiv.org/format/1906.01593">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2019/07/024">10.1088/1475-7516/2019/07/024 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Testing modified gravity at cosmological distances with LISA standard sirens </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Belgacem%2C+E">E. Belgacem</a>, <a href="/search/gr-qc?searchtype=author&query=Calcagni%2C+G">G. Calcagni</a>, <a href="/search/gr-qc?searchtype=author&query=Crisostomi%2C+M">M. Crisostomi</a>, <a href="/search/gr-qc?searchtype=author&query=Dalang%2C+C">C. Dalang</a>, <a href="/search/gr-qc?searchtype=author&query=Dirian%2C+Y">Y. Dirian</a>, <a href="/search/gr-qc?searchtype=author&query=Ezquiaga%2C+J+M">J. M. Ezquiaga</a>, <a href="/search/gr-qc?searchtype=author&query=Fasiello%2C+M">M. Fasiello</a>, <a href="/search/gr-qc?searchtype=author&query=Foffa%2C+S">S. Foffa</a>, <a href="/search/gr-qc?searchtype=author&query=Ganz%2C+A">A. Ganz</a>, <a href="/search/gr-qc?searchtype=author&query=Garcia-Bellido%2C+J">J. Garcia-Bellido</a>, <a href="/search/gr-qc?searchtype=author&query=Lombriser%2C+L">L. Lombriser</a>, <a href="/search/gr-qc?searchtype=author&query=Maggiore%2C+M">M. Maggiore</a>, <a href="/search/gr-qc?searchtype=author&query=Tamanini%2C+N">N. Tamanini</a>, <a href="/search/gr-qc?searchtype=author&query=Tasinato%2C+G">G. Tasinato</a>, <a href="/search/gr-qc?searchtype=author&query=Zumalacarregui%2C+M">M. Zumalacarregui</a>, <a href="/search/gr-qc?searchtype=author&query=Barausse%2C+E">E. Barausse</a>, <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">N. Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Bertacca%2C+D">D. Bertacca</a>, <a href="/search/gr-qc?searchtype=author&query=Klein%2C+A">A. Klein</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">S. Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Sakellariadou%2C+M">M. Sakellariadou</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1906.01593v2-abstract-short" style="display: inline;"> Modifications of General Relativity leave their imprint both on the cosmic expansion history through a non-trivial dark energy equation of state, and on the evolution of cosmological perturbations in the scalar and in the tensor sectors. In particular, the modification in the tensor sector gives rise to a notion of gravitational-wave (GW) luminosity distance, different from the standard electromag… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1906.01593v2-abstract-full').style.display = 'inline'; document.getElementById('1906.01593v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1906.01593v2-abstract-full" style="display: none;"> Modifications of General Relativity leave their imprint both on the cosmic expansion history through a non-trivial dark energy equation of state, and on the evolution of cosmological perturbations in the scalar and in the tensor sectors. In particular, the modification in the tensor sector gives rise to a notion of gravitational-wave (GW) luminosity distance, different from the standard electromagnetic luminosity distance, that can be studied with standard sirens at GW detectors such as LISA or third-generation ground based experiments. We discuss the predictions for modified GW propagation from some of the best studied theories of modified gravity, such as Horndeski or the more general degenerate higher order scalar-tensor (DHOST) theories, non-local infrared modifications of gravity, bigravity theories and the corresponding phenomenon of GW oscillation, as well as theories with extra or varying dimensions. We show that modified GW propagation is a completely generic phenomenon in modified gravity. We then use a simple parametrization of the effect in terms of two parameters $(螢_0,n)$, that is shown to fit well the results from a large class of models, to study the prospects of observing modified GW propagation using supermassive black hole binaries as standard sirens with LISA. We construct mock source catalogs and perform detailed Markov Chain Monte Carlo studies of the likelihood obtained from LISA standard sirens alone, as well as by combining them with CMB, BAO and SNe data to reduce the degeneracies between cosmological parameters. We find that the combination of LISA with the other cosmological datasets allows one to measure the parameter $螢_0$ that characterizes modified GW propagation to the percent level accuracy, sufficient to test several modified gravity theories. [Abridged] <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1906.01593v2-abstract-full').style.display = 'none'; document.getElementById('1906.01593v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 4 July, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 4 June, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">69 pages, 18 figures. References and additional explanations added. Matches published version</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> LISA CosWG-19-01; IFT-UAM-CSIC-19-79 </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> JCAP07(2019)024 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1905.05697">arXiv:1905.05697</a> <span> [<a href="https://arxiv.org/pdf/1905.05697">pdf</a>, <a href="https://arxiv.org/format/1905.05697">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Phenomenology">hep-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> </div> <p class="title is-5 mathjax"> Planck 2018 results. IX. Constraints on primordial non-Gaussianity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Planck+Collaboration"> Planck Collaboration</a>, <a href="/search/gr-qc?searchtype=author&query=Akrami%2C+Y">Y. Akrami</a>, <a href="/search/gr-qc?searchtype=author&query=Arroja%2C+F">F. Arroja</a>, <a href="/search/gr-qc?searchtype=author&query=Ashdown%2C+M">M. Ashdown</a>, <a href="/search/gr-qc?searchtype=author&query=Aumont%2C+J">J. Aumont</a>, <a href="/search/gr-qc?searchtype=author&query=Baccigalupi%2C+C">C. Baccigalupi</a>, <a href="/search/gr-qc?searchtype=author&query=Ballardini%2C+M">M. Ballardini</a>, <a href="/search/gr-qc?searchtype=author&query=Banday%2C+A+J">A. J. Banday</a>, <a href="/search/gr-qc?searchtype=author&query=Barreiro%2C+R+B">R. B. Barreiro</a>, <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">N. Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Basak%2C+S">S. Basak</a>, <a href="/search/gr-qc?searchtype=author&query=Benabed%2C+K">K. Benabed</a>, <a href="/search/gr-qc?searchtype=author&query=Bernard%2C+J+-">J. -P. Bernard</a>, <a href="/search/gr-qc?searchtype=author&query=Bersanelli%2C+M">M. Bersanelli</a>, <a href="/search/gr-qc?searchtype=author&query=Bielewicz%2C+P">P. Bielewicz</a>, <a href="/search/gr-qc?searchtype=author&query=Bond%2C+J+R">J. R. Bond</a>, <a href="/search/gr-qc?searchtype=author&query=Borrill%2C+J">J. Borrill</a>, <a href="/search/gr-qc?searchtype=author&query=Bouchet%2C+F+R">F. R. Bouchet</a>, <a href="/search/gr-qc?searchtype=author&query=Bucher%2C+M">M. Bucher</a>, <a href="/search/gr-qc?searchtype=author&query=Burigana%2C+C">C. Burigana</a>, <a href="/search/gr-qc?searchtype=author&query=Butler%2C+R+C">R. C. Butler</a>, <a href="/search/gr-qc?searchtype=author&query=Calabrese%2C+E">E. Calabrese</a>, <a href="/search/gr-qc?searchtype=author&query=Cardoso%2C+J+-">J. -F. Cardoso</a>, <a href="/search/gr-qc?searchtype=author&query=Casaponsa%2C+B">B. Casaponsa</a>, <a href="/search/gr-qc?searchtype=author&query=Challinor%2C+A">A. Challinor</a> , et al. (135 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1905.05697v1-abstract-short" style="display: inline;"> We analyse the Planck full-mission cosmic microwave background (CMB) temperature and E-mode polarization maps to obtain constraints on primordial non-Gaussianity (NG). We compare estimates obtained from separable template-fitting, binned, and modal bispectrum estimators, finding consistent values for the local, equilateral, and orthogonal bispectrum amplitudes. Our combined temperature and polariz… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.05697v1-abstract-full').style.display = 'inline'; document.getElementById('1905.05697v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1905.05697v1-abstract-full" style="display: none;"> We analyse the Planck full-mission cosmic microwave background (CMB) temperature and E-mode polarization maps to obtain constraints on primordial non-Gaussianity (NG). We compare estimates obtained from separable template-fitting, binned, and modal bispectrum estimators, finding consistent values for the local, equilateral, and orthogonal bispectrum amplitudes. Our combined temperature and polarization analysis produces the following results: f_NL^local = -0.9 +\- 5.1; f_NL^equil = -26 +\- 47; and f_NL^ortho = - 38 +\- 24 (68%CL, statistical). These results include the low-multipole (4 <= l < 40) polarization data, not included in our previous analysis, pass an extensive battery of tests, and are stable with respect to our 2015 measurements. Polarization bispectra display a significant improvement in robustness; they can now be used independently to set NG constraints. We consider a large number of additional cases, e.g. scale-dependent feature and resonance bispectra, isocurvature primordial NG, and parity-breaking models, where we also place tight constraints but do not detect any signal. The non-primordial lensing bispectrum is detected with an improved significance compared to 2015, excluding the null hypothesis at 3.5 sigma. We present model-independent reconstructions and analyses of the CMB bispectrum. Our final constraint on the local trispectrum shape is g_NLl^local = (-5.8 +\-6.5) x 10^4 (68%CL, statistical), while constraints for other trispectra are also determined. We constrain the parameter space of different early-Universe scenarios, including general single-field models of inflation, multi-field and axion field parity-breaking models. Our results provide a high-precision test for structure-formation scenarios, in complete agreement with the basic picture of the LambdaCDM cosmology regarding the statistics of the initial conditions (abridged). <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.05697v1-abstract-full').style.display = 'none'; document.getElementById('1905.05697v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 14 May, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">50 pages, 20 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1812.08197">arXiv:1812.08197</a> <span> [<a href="https://arxiv.org/pdf/1812.08197">pdf</a>, <a href="https://arxiv.org/format/1812.08197">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> </div> <p class="title is-5 mathjax"> Primordial Non-Gaussianity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Celoria%2C+M">Marco Celoria</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1812.08197v1-abstract-short" style="display: inline;"> Here we review the present status of modelling of and searching for primordial non-Gaussianity of cosmological perturbations. After introducing the models for non-Gaussianity generation during inflation, we discuss the search for non-Gaussian signatures in the Cosmic Microwave Background and in the Large-Scale Structure of the Universe. </span> <span class="abstract-full has-text-grey-dark mathjax" id="1812.08197v1-abstract-full" style="display: none;"> Here we review the present status of modelling of and searching for primordial non-Gaussianity of cosmological perturbations. After introducing the models for non-Gaussianity generation during inflation, we discuss the search for non-Gaussian signatures in the Cosmic Microwave Background and in the Large-Scale Structure of the Universe. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1812.08197v1-abstract-full').style.display = 'none'; document.getElementById('1812.08197v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 19 December, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">37 pages, 16 figures. To appear in Proceedings of the International School of Physics Enrico Fermi - Course 200, held at the Villa Monastero, Varenna, Lake Como (Italy) in July 2017. Eds. E. Coccia, J. Silk and N. Vittorio</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1812.03844">arXiv:1812.03844</a> <span> [<a href="https://arxiv.org/pdf/1812.03844">pdf</a>, <a href="https://arxiv.org/format/1812.03844">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2019/04/017">10.1088/1475-7516/2019/04/017 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> $螖N$ Formalism and Conserved Currents in Cosmology </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Pilo%2C+L">Luigi Pilo</a>, <a href="/search/gr-qc?searchtype=author&query=Rollo%2C+R">Rocco Rollo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1812.03844v3-abstract-short" style="display: inline;"> The $螖N$ formalism, based on the counting of the number of e-folds during inflation in different local patches of the Universe, has been introduced several years ago as a simple and physically intuitive approach to calculate (non-linear) curvature perturbations from inflation on large sales, without resorting to the full machinery of (higher-order) perturbation theory. Later on, it was claimed the… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1812.03844v3-abstract-full').style.display = 'inline'; document.getElementById('1812.03844v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1812.03844v3-abstract-full" style="display: none;"> The $螖N$ formalism, based on the counting of the number of e-folds during inflation in different local patches of the Universe, has been introduced several years ago as a simple and physically intuitive approach to calculate (non-linear) curvature perturbations from inflation on large sales, without resorting to the full machinery of (higher-order) perturbation theory. Later on, it was claimed the equivalence with the results found by introducing a conserved fully non-linear current $味_渭$, thereby allowing to directly connect perturbations during inflation to late-Universe observables. We discus some issues arising from the choice of the initial hyper-surface in the $螖N$ formalism. By using a novel exact expression for $味_渭$, valid for any barotropic fluid, we find that it is not in general related to the standard uniform density curvature perturbation $味$; such a result conflicts with the claimed equivalence with $螖N$ formalism. Moreover, a similar analysis is done for the proposed non-perturbative generalization ${\cal R}_渭$ of the comoving curvature perturbation ${\cal R}$. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1812.03844v3-abstract-full').style.display = 'none'; document.getElementById('1812.03844v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 1 April, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 6 December, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">19 pages, 1 figures. Final version accepted for publication in JCAP. Title slightly changed to avoid confusion with existing literature. Expanded content with the same conclusions</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1812.02667">arXiv:1812.02667</a> <span> [<a href="https://arxiv.org/pdf/1812.02667">pdf</a>, <a href="https://arxiv.org/ps/1812.02667">ps</a>, <a href="https://arxiv.org/format/1812.02667">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.99.064009">10.1103/PhysRevD.99.064009 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Hamiltonian analysis of mimetic scalar gravity revisited </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Ganz%2C+A">Alexander Ganz</a>, <a href="/search/gr-qc?searchtype=author&query=Karmakar%2C+P">Purnendu Karmakar</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Sorokin%2C+D">Dmitri Sorokin</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1812.02667v2-abstract-short" style="display: inline;"> We perform the Hamiltonian analysis of several mimetic gravity models and compare our results with those obtained previously by different authors. We verify that for healthy mimetic scalar-tensor theories the condition for the corresponding part of the Hamiltonian to be bounded from below is the positive value of the mimetic field energy density $位$. We show that for mimetic dark matter possessing… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1812.02667v2-abstract-full').style.display = 'inline'; document.getElementById('1812.02667v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1812.02667v2-abstract-full" style="display: none;"> We perform the Hamiltonian analysis of several mimetic gravity models and compare our results with those obtained previously by different authors. We verify that for healthy mimetic scalar-tensor theories the condition for the corresponding part of the Hamiltonian to be bounded from below is the positive value of the mimetic field energy density $位$. We show that for mimetic dark matter possessing a shift symmetry the mimetic energy density remains positive in time, provided appropriate boundary conditions are imposed on its initial value, while in models without shift symmetry the positive energy density can be maintained by simply replacing $位\to e^位$. The same result also applies to mimetic $f(R)$ gravity, which is healthy if the usual stability conditions of the standard $f(R)$ gravity are assumed and $位>0$. In contrast, if we add mimetic matter to an unhealthy seed action, the resulting mimetic gravity theory remains, in general, unstable. As an example, we consider a scalar-tensor theory with the higher-derivative term $(\Box \varphi)^2$, which contains an Ostrogradski ghost. We also revisit results regarding stability issues of linear perturbations around the FLRW background of the mimetic dark matter in the presence of ordinary scalar matter. We find that the presence of conventional matter does not revive dynamical ghost modes (at least in the UV limit). The modes, whose Hamiltonian is not positive definite, are non-propagating (have zero sound speed) and are associated with the mimetic matter itself. They are already present in the case in which the ordinary scalar fluid is absent, causing a growth of dust overdensity. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1812.02667v2-abstract-full').style.display = 'none'; document.getElementById('1812.02667v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 18 December, 2018; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 6 December, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">40 pages, 0 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 99, 064009 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1809.03528">arXiv:1809.03528</a> <span> [<a href="https://arxiv.org/pdf/1809.03528">pdf</a>, <a href="https://arxiv.org/format/1809.03528">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2018/09/039">10.1088/1475-7516/2018/09/039 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> GW$\times$LSS: Chasing the Progenitors of Merging Binary Black Holes </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Scelfo%2C+G">Giulio Scelfo</a>, <a href="/search/gr-qc?searchtype=author&query=Bellomo%2C+N">Nicola Bellomo</a>, <a href="/search/gr-qc?searchtype=author&query=Raccanelli%2C+A">Alvise Raccanelli</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Verde%2C+L">Licia Verde</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1809.03528v2-abstract-short" style="display: inline;"> Are the stellar-mass merging binary black holes, recently detected by their gravitational wave signal, of stellar or primordial origin? Answering this question will have profound implications for our understanding of the Universe, including the nature of dark matter, the early Universe and stellar evolution. We build on the idea that the clustering properties of merging binary black holes can prov… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1809.03528v2-abstract-full').style.display = 'inline'; document.getElementById('1809.03528v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1809.03528v2-abstract-full" style="display: none;"> Are the stellar-mass merging binary black holes, recently detected by their gravitational wave signal, of stellar or primordial origin? Answering this question will have profound implications for our understanding of the Universe, including the nature of dark matter, the early Universe and stellar evolution. We build on the idea that the clustering properties of merging binary black holes can provide information about binary formation mechanisms and origin. The cross-correlation of galaxy with gravitational wave catalogues carries information about whether black hole mergers trace more closely the distribution of dark matter -- indicative of primordial origin -- or that of stars harboured in luminous and massive galaxies -- indicative of a stellar origin. We forecast the detectability of such signal for several forthcoming and future gravitational wave interferometers and galaxy surveys, including, for the first time in such analyses, an accurate modelling for the different merger rates, lensing magnification and other general relativistic effects. Our results show that forthcoming experiments could allow us to test most of the parameter space of the still viable models investigated, and shed more light on the issue of binary black hole origin and evolution. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1809.03528v2-abstract-full').style.display = 'none'; document.getElementById('1809.03528v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 May, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 10 September, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">34 pages, 8 figures. Matches the published version. Added link to Multi_CLASS code</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1809.03496">arXiv:1809.03496</a> <span> [<a href="https://arxiv.org/pdf/1809.03496">pdf</a>, <a href="https://arxiv.org/ps/1809.03496">ps</a>, <a href="https://arxiv.org/format/1809.03496">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2019/01/056">10.1088/1475-7516/2019/01/056 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Gravity in mimetic scalar-tensor theories after GW170817 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Ganz%2C+A">Alexander Ganz</a>, <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">Nicola Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Karmakar%2C+P">Purnendu Karmakar</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1809.03496v1-abstract-short" style="display: inline;"> We derive the most general mimetic scalar-tensor theory assuming a healthy "seed" action and accounting for the constraints on the speed of gravitational-wave propagation arising from the GW170817 event. By analysing linear perturbations around a flat FLRW background in this model, we obtain a suitable form of the Poisson equation, which allows us to calculate the effective gravitational constant… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1809.03496v1-abstract-full').style.display = 'inline'; document.getElementById('1809.03496v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1809.03496v1-abstract-full" style="display: none;"> We derive the most general mimetic scalar-tensor theory assuming a healthy "seed" action and accounting for the constraints on the speed of gravitational-wave propagation arising from the GW170817 event. By analysing linear perturbations around a flat FLRW background in this model, we obtain a suitable form of the Poisson equation, which allows us to calculate the effective gravitational constant felt by "ordinary" matter. By restricting to a minimally coupled model, such an effective gravitational constant is equivalent to that obtained within General Relativity, with cold dark matter plus a perfect fluid dark energy component, with vanishing sound speed. Assuming, further, a $螞$CDM background, the effective gravitational constant cannot be distinguished from that of the standard $螞$CDM model, at linear order. For the full non-minimally coupled mimetic gravity model we obtain a non-vanishing gravitational slip and an effective gravitational constant which always differs from that of standard $螞$CDM. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1809.03496v1-abstract-full').style.display = 'none'; document.getElementById('1809.03496v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 10 September, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">20 pages, 0 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1804.06298">arXiv:1804.06298</a> <span> [<a href="https://arxiv.org/pdf/1804.06298">pdf</a>, <a href="https://arxiv.org/ps/1804.06298">ps</a>, <a href="https://arxiv.org/format/1804.06298">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.98.023518">10.1103/PhysRevD.98.023518 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Photon-graviton scattering: A new way to detect anisotropic gravitational waves? </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">Nicola Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Hoseinpour%2C+A">Ahmad Hoseinpour</a>, <a href="/search/gr-qc?searchtype=author&query=Orlando%2C+G">Giorgio Orlando</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Zarei%2C+M">Moslem Zarei</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1804.06298v2-abstract-short" style="display: inline;"> Gravitons are the quantum counterparts of gravitational waves in low-energy theories of gravity. Using Feynman rules one can compute scattering amplitudes describing the interaction between gravitons and other fields. Here, we consider the interaction between gravitons and photons. Using the quantum Boltzmann equation formalism, we derive fully general equations describing the radiation transfer o… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1804.06298v2-abstract-full').style.display = 'inline'; document.getElementById('1804.06298v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1804.06298v2-abstract-full" style="display: none;"> Gravitons are the quantum counterparts of gravitational waves in low-energy theories of gravity. Using Feynman rules one can compute scattering amplitudes describing the interaction between gravitons and other fields. Here, we consider the interaction between gravitons and photons. Using the quantum Boltzmann equation formalism, we derive fully general equations describing the radiation transfer of photon polarization, due to the forward scattering with gravitons. We show that the Q and U photon linear polarization modes couple with the V photon circular polarization mode, if gravitons have anisotropies in their power-spectrum statistics. As an example, we apply our results to the case of primordial gravitons, considering models of inflation where an anisotropic primordial graviton distribution is produced. Finally, we evaluate the effect on cosmic microwave background (CMB) polarization, showing that in general the expected effects on the observable CMB frequencies are very small. However, our result is promising, since it could provide a novel tool for detecting anisotropic backgrounds of gravitational waves, as well as for getting further insight on the physics of gravitational waves. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1804.06298v2-abstract-full').style.display = 'none'; document.getElementById('1804.06298v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 17 July, 2018; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 17 April, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">15 pages, 1 figure. v2: references added, typos corrected, replaced to match published version in PRD</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 98, 023518 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1801.09415">arXiv:1801.09415</a> <span> [<a href="https://arxiv.org/pdf/1801.09415">pdf</a>, <a href="https://arxiv.org/format/1801.09415">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Phenomenology">hep-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2018/03/016">10.1088/1475-7516/2018/03/016 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Primordial Black Holes from Inflation and non-Gaussianity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Franciolini%2C+G">G. Franciolini</a>, <a href="/search/gr-qc?searchtype=author&query=Kehagias%2C+A">A. Kehagias</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">S. Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Riotto%2C+A">A. Riotto</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1801.09415v2-abstract-short" style="display: inline;"> Primordial black holes may owe their origin to the small-scale enhancement of the comoving curvature perturbation generated during inflation. Their mass fraction at formation is markedly sensitive to possible non-Gaussianities in such large, but rare fluctuations. We discuss a path-integral formulation which provides the exact mass fraction of primordial black holes at formation in the presence of… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1801.09415v2-abstract-full').style.display = 'inline'; document.getElementById('1801.09415v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1801.09415v2-abstract-full" style="display: none;"> Primordial black holes may owe their origin to the small-scale enhancement of the comoving curvature perturbation generated during inflation. Their mass fraction at formation is markedly sensitive to possible non-Gaussianities in such large, but rare fluctuations. We discuss a path-integral formulation which provides the exact mass fraction of primordial black holes at formation in the presence of non-Gaussianity. Through a couple of classes of models, one based on single-field inflation and the other on spectator fields, we show that restricting to a Gaussian statistics may lead to severe inaccuracies in the estimate of the mass fraction as well as on the clustering properties of the primordial black holes. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1801.09415v2-abstract-full').style.display = 'none'; document.getElementById('1801.09415v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 March, 2018; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 29 January, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">21 pages, 2 figures, v2: matching published version</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> JCAP03(2018)016 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1712.04002">arXiv:1712.04002</a> <span> [<a href="https://arxiv.org/pdf/1712.04002">pdf</a>, <a href="https://arxiv.org/format/1712.04002">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2018/05/048">10.1088/1475-7516/2018/05/048 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Cosmic structures and gravitational waves in ghost-free scalar-tensor theories of gravity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">Nicola Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Karmakar%2C+P">Purnendu Karmakar</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a>, <a href="/search/gr-qc?searchtype=author&query=Scomparin%2C+M">Mattia Scomparin</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1712.04002v1-abstract-short" style="display: inline;"> We study cosmic structures in the quadratic Degenerate Higher Order Scalar Tensor (qDHOST) model, which has been proposed as the most general scalar-tensor theory (up to quadratic dependence on the covariant derivatives of the scalar field), which is not plagued by the presence of ghost instabilities. We then study a static, spherically symmetric object embedded in de Sitter space-time for the qDH… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1712.04002v1-abstract-full').style.display = 'inline'; document.getElementById('1712.04002v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1712.04002v1-abstract-full" style="display: none;"> We study cosmic structures in the quadratic Degenerate Higher Order Scalar Tensor (qDHOST) model, which has been proposed as the most general scalar-tensor theory (up to quadratic dependence on the covariant derivatives of the scalar field), which is not plagued by the presence of ghost instabilities. We then study a static, spherically symmetric object embedded in de Sitter space-time for the qDHOST model. This model exhibits breaking of the Vainshtein mechanism inside the cosmic structure and Schwarzschild-de Sitter space-time outside, where General Relativity (GR) can be recovered within the Vainshtein radius. We then look for the conditions on the parameters on the considered qDHOST scenario which ensure the validity of the Vainshtein screening mechanism inside the object and the fulfilment of the recent GW170817/GRB170817A constraint on the speed of propagation of gravitational waves. We find that these two constraints rule out the same set of parameters, corresponding to the Lagrangians that are quadratic in second-order derivatives of the scalar field, for the shift symmetric qDHOST. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1712.04002v1-abstract-full').style.display = 'none'; document.getElementById('1712.04002v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 11 December, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">16 pages</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1711.07984">arXiv:1711.07984</a> <span> [<a href="https://arxiv.org/pdf/1711.07984">pdf</a>, <a href="https://arxiv.org/format/1711.07984">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2018/04/002">10.1088/1475-7516/2018/04/002 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Peering beyond the horizon with standard sirens and redshift drift </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Jimenez%2C+R">Raul Jimenez</a>, <a href="/search/gr-qc?searchtype=author&query=Raccanelli%2C+A">Alvise Raccanelli</a>, <a href="/search/gr-qc?searchtype=author&query=Verde%2C+L">Licia Verde</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1711.07984v2-abstract-short" style="display: inline;"> An interesting test on the nature of the Universe is to measure the global spatial curvature of the metric in a model independent way, at a level of $|惟_k|<10^{-4}$, or, if possible, at the cosmic variance level of the amplitude of the CMB fluctuations $|惟_k|\approx10^{-5}$. A limit of $|惟_k|<10^{-4}$ would yield stringent tests on several models of inflation. Further, improving the constraint by… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1711.07984v2-abstract-full').style.display = 'inline'; document.getElementById('1711.07984v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1711.07984v2-abstract-full" style="display: none;"> An interesting test on the nature of the Universe is to measure the global spatial curvature of the metric in a model independent way, at a level of $|惟_k|<10^{-4}$, or, if possible, at the cosmic variance level of the amplitude of the CMB fluctuations $|惟_k|\approx10^{-5}$. A limit of $|惟_k|<10^{-4}$ would yield stringent tests on several models of inflation. Further, improving the constraint by an order of magnitude would help in reducing "model confusion" in standard parameter estimation. Moreover, if the curvature is measured to be at the value of the amplitude of the CMB fluctuations, it would offer a powerful test on the inflationary paradigm and would indicate that our Universe must be significantly larger than the current horizon. On the contrary, in the context of standard inflation, measuring a value above CMB fluctuations will lead us to conclude that the Universe is not much larger than the current observed horizon, this can also be interpreted as the presence of large fluctuations outside the horizon. However, it has proven difficult, so far, to find observables that can achieve such level of accuracy, and, most of all, be model-independent. Here we propose a method that can in principle achieve that, this is done by making minimal assumptions and using distance probes that are cosmology-independent: gravitational waves, redshift drift and cosmic chronometers. We discuss what kind of observations are needed in principle to achieve the desired accuracy. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1711.07984v2-abstract-full').style.display = 'none'; document.getElementById('1711.07984v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 March, 2018; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 21 November, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Matches version published in JCAP, minor changes, conclusions unchanged</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Journal of Cosmology and Astroparticle Physics, Issue 04, article id. 002 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1708.01850">arXiv:1708.01850</a> <span> [<a href="https://arxiv.org/pdf/1708.01850">pdf</a>, <a href="https://arxiv.org/format/1708.01850">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2018/05/050">10.1088/1475-7516/2018/05/050 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Large-scale structure in mimetic Horndeski gravity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Arroja%2C+F">Frederico Arroja</a>, <a href="/search/gr-qc?searchtype=author&query=Okumura%2C+T">Teppei Okumura</a>, <a href="/search/gr-qc?searchtype=author&query=Bartolo%2C+N">Nicola Bartolo</a>, <a href="/search/gr-qc?searchtype=author&query=Karmakar%2C+P">Purnendu Karmakar</a>, <a href="/search/gr-qc?searchtype=author&query=Matarrese%2C+S">Sabino Matarrese</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1708.01850v2-abstract-short" style="display: inline;"> In this paper, we propose to use the mimetic Horndeski model as a model for the dark universe. Both cold dark matter (CDM) and dark energy (DE) phenomena are described by a single component, the mimetic field. In linear theory, we show that this component effectively behaves like a perfect fluid with zero sound speed and clusters on all scales. For the simpler mimetic cubic Horndeski model, if the… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1708.01850v2-abstract-full').style.display = 'inline'; document.getElementById('1708.01850v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1708.01850v2-abstract-full" style="display: none;"> In this paper, we propose to use the mimetic Horndeski model as a model for the dark universe. Both cold dark matter (CDM) and dark energy (DE) phenomena are described by a single component, the mimetic field. In linear theory, we show that this component effectively behaves like a perfect fluid with zero sound speed and clusters on all scales. For the simpler mimetic cubic Horndeski model, if the background expansion history is chosen to be identical to a perfect fluid DE (PFDE) then the mimetic model predicts the same power spectrum of the Newtonian potential as the PFDE model with zero sound speed. In particular, if the background is chosen to be the same as that of LCDM, then also in this case the power spectrum of the Newtonian potential in the mimetic model becomes indistinguishable from the power spectrum in LCDM on linear scales. A different conclusion may be found in the case of non-adiabatic perturbations. We also discuss the distinguishability, using power spectrum measurements from LCDM N-body simulations as a proxy for future observations, between these mimetic models and other popular models of DE. For instance, we find that if the background has an equation of state equal to -0.95 then we will be able to distinguish the mimetic model from the PFDE model with unity sound speed. On the other hand, it will be hard to do this distinction with respect to the LCDM model. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1708.01850v2-abstract-full').style.display = 'none'; document.getElementById('1708.01850v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 18 May, 2018; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 6 August, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">v1: 17 pages, 6 figures. v2: minor changes, comments added, replaced to match published version</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> JCAP05(2018)050 </p> </li> </ol> <nav class="pagination is-small is-centered breathe-horizontal" role="navigation" aria-label="pagination"> <a href="" class="pagination-previous is-invisible">Previous </a> <a href="/search/?searchtype=author&query=Matarrese%2C+S&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Matarrese%2C+S&start=0" class="pagination-link is-current" aria-label="Goto page 1">1 </a> </li> <li> <a href="/search/?searchtype=author&query=Matarrese%2C+S&start=50" class="pagination-link " aria-label="Page 2" aria-current="page">2 </a> </li> <li> <a href="/search/?searchtype=author&query=Matarrese%2C+S&start=100" class="pagination-link " aria-label="Page 3" aria-current="page">3 </a> </li> </ul> </nav> <div class="is-hidden-tablet">  <span class="help" style="display: inline-block;"><a href="https://github.com/arXiv/arxiv-search/releases">Search v0.5.6 released 2020-02-24</a>  </span> </div> 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