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Gravitational wave luminosity distance-weighted anisotropies
Authors:
A. Begnoni,
L. Valbusa Dall'Armi,
D. Bertacca,
A. Raccanelli
Abstract:
Measurements of the luminosity distance of propagating gravitational waves can provide invaluable information on the geometry and content of our Universe. Due to the clustering of cosmic structures, in realistic situations we need to average the luminosity distance of events coming from patches inside a volume. In this work we evaluate, in a gauge-invariant and fully-relativistic treatment, the im…
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Measurements of the luminosity distance of propagating gravitational waves can provide invaluable information on the geometry and content of our Universe. Due to the clustering of cosmic structures, in realistic situations we need to average the luminosity distance of events coming from patches inside a volume. In this work we evaluate, in a gauge-invariant and fully-relativistic treatment, the impact of cosmological perturbations on such averaging process. We find that clustering, lensing and peculiar velocity effects impact estimates for future detectors such as Einstein Telescope, Cosmic Explorer, the Big Bang Observer and DECIGO. The signal-to-noise ratio of the angular power spectrum of the average luminosity distance over all the redshift bins is 17 in the case of binary black holes detected by Einstein Telescope and Cosmic Explorer. We also provide fitting formulas for the corrections to the average luminosity distance due to general relativistic effects.
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Submitted 21 October, 2024; v1 submitted 18 April, 2024;
originally announced April 2024.
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Primordial black holes and their gravitational-wave signatures
Authors:
Eleni Bagui,
Sebastien Clesse,
Valerio De Luca,
Jose María Ezquiaga,
Gabriele Franciolini,
Juan García-Bellido,
Cristian Joana,
Rajeev Kumar Jain,
Sachiko Kuroyanagi,
Ilia Musco,
Theodoros Papanikolaou,
Alvise Raccanelli,
Sébastien Renaux-Petel,
Antonio Riotto,
Ester Ruiz Morales,
Marco Scalisi,
Olga Sergijenko,
Caner Unal,
Vincent Vennin,
David Wands
Abstract:
In the recent years, primordial black holes (PBHs) have emerged as one of the most interesting and hotly debated topics in cosmology. Among other possibilities, PBHs could explain both some of the signals from binary black hole mergers observed in gravitational wave detectors and an important component of the dark matter in the Universe. Significant progress has been achieved both on the theory si…
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In the recent years, primordial black holes (PBHs) have emerged as one of the most interesting and hotly debated topics in cosmology. Among other possibilities, PBHs could explain both some of the signals from binary black hole mergers observed in gravitational wave detectors and an important component of the dark matter in the Universe. Significant progress has been achieved both on the theory side and from the point of view of observations, including new models and more accurate calculations of PBH formation, evolution, clustering, merger rates, as well as new astrophysical and cosmological probes. In this work, we review, analyse and combine the latest developments in order to perform end-to-end calculations of the various gravitational wave signatures of PBHs. Different ways to distinguish PBHs from stellar black holes are emphasized. Finally, we discuss their detectability with LISA, the first planned gravitational-wave observatory in space.
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Submitted 30 October, 2023;
originally announced October 2023.
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The effect of outflows on CMB bounds from Primordial Black Hole accretion
Authors:
Lorenzo Piga,
Matteo Lucca,
Nicola Bellomo,
Valentì Bosch-Ramon,
Sabino Matarrese,
Alvise Raccanelli,
Licia Verde
Abstract:
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…
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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.
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Submitted 26 October, 2022;
originally announced October 2022.
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New Horizons for Fundamental Physics with LISA
Authors:
K. G. Arun,
Enis Belgacem,
Robert Benkel,
Laura Bernard,
Emanuele Berti,
Gianfranco Bertone,
Marc Besancon,
Diego Blas,
Christian G. Böhmer,
Richard Brito,
Gianluca Calcagni,
Alejandro Cardenas-Avendaño,
Katy Clough,
Marco Crisostomi,
Valerio De Luca,
Daniela Doneva,
Stephanie Escoffier,
Jose Maria Ezquiaga,
Pedro G. Ferreira,
Pierre Fleury,
Stefano Foffa,
Gabriele Franciolini,
Noemi Frusciante,
Juan García-Bellido,
Carlos Herdeiro
, et al. (116 additional authors not shown)
Abstract:
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…
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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.
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Submitted 3 May, 2022;
originally announced May 2022.
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CLASS_GWB: robust modeling of the astrophysical gravitational wave background anisotropies
Authors:
Nicola Bellomo,
Daniele Bertacca,
Alexander C. Jenkins,
Sabino Matarrese,
Alvise Raccanelli,
Tania Regimbau,
Angelo Ricciardone,
Mairi Sakellariadou
Abstract:
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…
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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.
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Submitted 26 October, 2021;
originally announced October 2021.
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Gravitational waves $\times$ HI intensity mapping: cosmological and astrophysical applications
Authors:
Giulio Scelfo,
Marta Spinelli,
Alvise Raccanelli,
Lumen Boco,
Andrea Lapi,
Matteo Viel
Abstract:
Two of the most rapidly growing observables in cosmology and astrophysics are gravitational waves (GW) and the neutral hydrogen (HI) distribution. In this work, we investigate the cross-correlation between resolved gravitational wave detections and HI signal from intensity mapping (IM) experiments. By using a tomographic approach with angular power spectra, including all projection effects, we exp…
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Two of the most rapidly growing observables in cosmology and astrophysics are gravitational waves (GW) and the neutral hydrogen (HI) distribution. In this work, we investigate the cross-correlation between resolved gravitational wave detections and HI signal from intensity mapping (IM) experiments. By using a tomographic approach with angular power spectra, including all projection effects, we explore possible applications of the combination of the Einstein Telescope and the SKAO intensity mapping surveys. We focus on three main topics: \textit{(i)} statistical inference of the observed redshift distribution of GWs; \textit{(ii)} constraints on dynamical dark energy models as an example of cosmological studies; \textit{(iii)} determination of the nature of the progenitors of merging binary black holes, distinguishing between primordial and astrophysical origin. Our results show that: \textit{(i)} the GW redshift distribution can be calibrated with good accuracy at low redshifts, without any assumptions on cosmology or astrophysics, potentially providing a way to probe astrophysical and cosmological models; \textit{(ii)} the constrains on the dynamical dark energy parameters are competitive with IM-only experiments, in a complementary way and potentially with less systematics; \textit{(iii)} it will be possible to detect a relatively small abundance of primordial black holes within the gravitational waves from resolved mergers. Our results extend towards $\mathrm{GW \times IM}$ the promising field of multi-tracing cosmology and astrophysics, which has the major advantage of allowing scientific investigations in ways that would not be possible by looking at single observables separately.
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Submitted 10 January, 2022; v1 submitted 17 June, 2021;
originally announced June 2021.
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Prospects for Fundamental Physics with LISA
Authors:
Enrico Barausse,
Emanuele Berti,
Thomas Hertog,
Scott A. Hughes,
Philippe Jetzer,
Paolo Pani,
Thomas P. Sotiriou,
Nicola Tamanini,
Helvi Witek,
Kent Yagi,
Nicolas Yunes,
T. Abdelsalhin,
A. Achucarro,
K. V. Aelst,
N. Afshordi,
S. Akcay,
L. Annulli,
K. G. Arun,
I. Ayuso,
V. Baibhav,
T. Baker,
H. Bantilan,
T. Barreiro,
C. Barrera-Hinojosa,
N. Bartolo
, et al. (296 additional authors not shown)
Abstract:
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…
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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.
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Submitted 27 April, 2020; v1 submitted 27 January, 2020;
originally announced January 2020.
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Projection effects on the observed angular spectrum of the astrophysical stochastic gravitational wave background
Authors:
Daniele Bertacca,
Angelo Ricciardone,
Nicola Bellomo,
Alexander C. Jenkins,
Sabino Matarrese,
Alvise Raccanelli,
Tania Regimbau,
Mairi Sakellariadou
Abstract:
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…
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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.
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Submitted 1 August, 2022; v1 submitted 25 September, 2019;
originally announced September 2019.
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Unveiling the Gravitational Universe at μ-Hz Frequencies
Authors:
Alberto Sesana,
Natalia Korsakova,
Manuel Arca Sedda,
Vishal Baibhav,
Enrico Barausse,
Simon Barke,
Emanuele Berti,
Matteo Bonetti,
Pedro R. Capelo,
Chiara Caprini,
Juan Garcia-Bellido,
Zoltan Haiman,
Karan Jani,
Oliver Jennrich,
Peter Johansson,
Fazeel Mahmood Khan,
Valeriya Korol,
Astrid Lamberts,
Alessandro Lupi,
Alberto Mangiagli,
Lucio Mayer,
Germano Nardini,
Fabio Pacucci,
Antoine Petiteau,
Alvise Raccanelli
, et al. (9 additional authors not shown)
Abstract:
We propose a space-based interferometer surveying the gravitational wave (GW) sky in the milli-Hz to $μ$-Hz frequency range. By the 2040s', the $μ$-Hz frequency band, bracketed in between the Laser Interferometer Space Antenna (LISA) and pulsar timing arrays, will constitute the largest gap in the coverage of the astrophysically relevant GW spectrum. Yet many outstanding questions related to astro…
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We propose a space-based interferometer surveying the gravitational wave (GW) sky in the milli-Hz to $μ$-Hz frequency range. By the 2040s', the $μ$-Hz frequency band, bracketed in between the Laser Interferometer Space Antenna (LISA) and pulsar timing arrays, will constitute the largest gap in the coverage of the astrophysically relevant GW spectrum. Yet many outstanding questions related to astrophysics and cosmology are best answered by GW observations in this band. We show that a $μ$-Hz GW detector will be a truly overarching observatory for the scientific community at large, greatly extending the potential of LISA. Conceived to detect massive black hole binaries from their early inspiral with high signal-to-noise ratio, and low-frequency stellar binaries in the Galaxy, this instrument will be a cornerstone for multimessenger astronomy from the solar neighbourhood to the high-redshift Universe.
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Submitted 29 August, 2019;
originally announced August 2019.
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Lyman-$α$ forest constraints on Primordial Black Holes as Dark Matter
Authors:
Riccardo Murgia,
Giulio Scelfo,
Matteo Viel,
Alvise Raccanelli
Abstract:
The renewed interest in the possibility that primordial black holes (PBHs) may constitute a significant part of the dark matter has motivated revisiting old observational constraints, as well as developing new ones. We present new limits on the PBH abundance, from a comprehensive analysis of high-resolution, high-redshift Lyman-$α$ forest data. Poisson fluctuations in the PBH number density induce…
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The renewed interest in the possibility that primordial black holes (PBHs) may constitute a significant part of the dark matter has motivated revisiting old observational constraints, as well as developing new ones. We present new limits on the PBH abundance, from a comprehensive analysis of high-resolution, high-redshift Lyman-$α$ forest data. Poisson fluctuations in the PBH number density induce a small-scale power enhancement which departs from the standard cold dark matter prediction. Using a grid of hydrodynamic simulations exploring different values of astrophysical parameters, {we obtain a marginalized upper limit on the PBH mass of $f_{\rm PBH}M_{\rm PBH} \sim 60~M_{\odot}$ at $2σ$, when a Gaussian prior on the reionization redshift is imposed, preventing its posterior distribution to peak on very high values, which are disfavoured by the most recent estimates obtained both through Cosmic Microwave Background and Inter-Galactic Medium observations. Such bound weakens to $f_{\rm PBH}M_{\rm PBH} \sim 170~M_{\odot}$, when a conservative flat prior is instead assumed. Both limits significantly improves previous constraints from the same physical observable.} We also extend our predictions to non-monochromatic PBH mass distributions, ruling out large regions of the parameter space for some of the most viable PBH extended mass functions.
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Submitted 18 August, 2019; v1 submitted 25 March, 2019;
originally announced March 2019.
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GW$\times$LSS: Chasing the Progenitors of Merging Binary Black Holes
Authors:
Giulio Scelfo,
Nicola Bellomo,
Alvise Raccanelli,
Sabino Matarrese,
Licia Verde
Abstract:
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…
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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.
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Submitted 26 May, 2020; v1 submitted 10 September, 2018;
originally announced September 2018.
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Peering beyond the horizon with standard sirens and redshift drift
Authors:
Raul Jimenez,
Alvise Raccanelli,
Licia Verde,
Sabino Matarrese
Abstract:
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 $|Ω_k|<10^{-4}$, or, if possible, at the cosmic variance level of the amplitude of the CMB fluctuations $|Ω_k|\approx10^{-5}$. A limit of $|Ω_k|<10^{-4}$ would yield stringent tests on several models of inflation. Further, improving the constraint by…
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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 $|Ω_k|<10^{-4}$, or, if possible, at the cosmic variance level of the amplitude of the CMB fluctuations $|Ω_k|\approx10^{-5}$. A limit of $|Ω_k|<10^{-4}$ 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.
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Submitted 26 March, 2018; v1 submitted 21 November, 2017;
originally announced November 2017.
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Effects of primordial black holes quantum gravity decay on galaxy clustering
Authors:
Alvise Raccanelli,
Francesca Vidotto,
Licia Verde
Abstract:
It has been recently suggested that small mass black holes (BHs) may become unstable due to quantum-gravitational effects and eventually decay, producing radiation, on a timescale shorter than the Hawking evaporation time. We argue that the existence of a population of low-mass Primordial Black Holes (PBHs) acting as a fraction of the Universe dark matter component can be used to test proposed mod…
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It has been recently suggested that small mass black holes (BHs) may become unstable due to quantum-gravitational effects and eventually decay, producing radiation, on a timescale shorter than the Hawking evaporation time. We argue that the existence of a population of low-mass Primordial Black Holes (PBHs) acting as a fraction of the Universe dark matter component can be used to test proposed models of quantum decay of BHs via their effect on galaxy number counts. We study what constraints future galaxy clustering measurements can set on quantum-gravity parameters governing the BH lifetime and PBH abundance. In case of no detection of such effects, this would rule out either the existence of a non-negligible number of small PBHs, or the BH quantum decay scenario (or both). In case of independent observations of PBHs, the observables discussed here could be used to study the quantum effects that modify the final fate of BHs.
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Submitted 8 August, 2017;
originally announced August 2017.
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Relativistic wide-angle galaxy bispectrum on the light-cone
Authors:
Daniele Bertacca,
Alvise Raccanelli,
Nicola Bartolo,
Michele Liguori,
Sabino Matarrese,
Licia Verde
Abstract:
Given the important role that the galaxy bispectrum has recently acquired in cosmology and the scale and precision of forthcoming galaxy clustering observations, it is timely to derive the full expression of the large-scale bispectrum going beyond approximated treatments which neglect integrated terms or higher-order bias terms or use the Limber approximation. On cosmological scales, relativistic…
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Given the important role that the galaxy bispectrum has recently acquired in cosmology and the scale and precision of forthcoming galaxy clustering observations, it is timely to derive the full expression of the large-scale bispectrum going beyond approximated treatments which neglect integrated terms or higher-order bias terms or use the Limber approximation. On cosmological scales, relativistic effects that arise from observing on the past light-cone alter the observed galaxy number counts, therefore leaving their imprints on N-point correlators at all orders. In this paper we compute for the first time the bispectrum including all general relativistic, local and integrated, effects at second order, the tracers' bias at second order, geometric effects as well as the primordial non-Gaussianity contribution. This is timely considering that future surveys will probe scales comparable to the horizon where approximations widely used currently may not hold; neglecting these effects may introduce biases in estimation of cosmological parameters as well as primordial non-Gaussianity.
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Submitted 27 January, 2018; v1 submitted 25 May, 2017;
originally announced May 2017.
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Cosmological perturbation effects on gravitational-wave luminosity distance estimates
Authors:
Daniele Bertacca,
Alvise Raccanelli,
Nicola Bartolo,
Sabino Matarrese
Abstract:
Waveforms of gravitational waves provide information about a variety of parameters for the binary system merging. However, standard calculations have been performed assuming a FLRW universe with no perturbations. In reality this assumption should be dropped: we show that the inclusion of cosmological perturbations translates into corrections to the estimate of astrophysical parameters derived for…
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Waveforms of gravitational waves provide information about a variety of parameters for the binary system merging. However, standard calculations have been performed assuming a FLRW universe with no perturbations. In reality this assumption should be dropped: we show that the inclusion of cosmological perturbations translates into corrections to the estimate of astrophysical parameters derived for the merging binary systems. We compute corrections to the estimate of the luminosity distance due to velocity, volume, lensing and gravitational potential effects. Our results show that the amplitude of the corrections will be negligible for current instruments, mildly important for experiments like the planned DECIGO, and very important for future ones such as the Big Bang Observer.
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Submitted 9 October, 2019; v1 submitted 6 February, 2017;
originally announced February 2017.
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Gravitational wave astronomy with radio galaxy surveys
Authors:
Alvise Raccanelli
Abstract:
In the next decade, new astrophysical instruments will deliver the first large-scale maps of gravitational waves and radio sources. Therefore, it is timely to investigate the possibility to combine them to provide new and complementary ways to study the Universe. Using simulated catalogues appropriate to the planned surveys, it is possible to predict measurements of the cross-correlation between r…
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In the next decade, new astrophysical instruments will deliver the first large-scale maps of gravitational waves and radio sources. Therefore, it is timely to investigate the possibility to combine them to provide new and complementary ways to study the Universe. Using simulated catalogues appropriate to the planned surveys, it is possible to predict measurements of the cross-correlation between radio sources and GW maps and the effects of a stochastic gravitational wave background on galaxy maps. Effects of GWs on the large scale structure of the Universe can be used to investigate the nature of the progenitors of merging BHs, the validity of Einstein's General Relativity, models for dark energy, and detect a stochastic background of GW. The results obtained show that the galaxy-GW cross-correlation can provide useful information in the near future, while the detection of tensor perturbation effects on the LSS will require instruments with capabilities beyond the currently planned next generation of radio arrays. Nevertheless, any information from the combination of galaxy surveys with GW maps will help provide additional information for the newly born gravitational wave astronomy.
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Submitted 29 September, 2016;
originally announced September 2016.
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Orbital eccentricities in primordial black holes binaries
Authors:
Ilias Cholis,
Ely D. Kovetz,
Yacine Ali-Haïmoud,
Simeon Bird,
Marc Kamionkowski,
Julian B. Muñoz,
Alvise Raccanelli
Abstract:
It was recently suggested that the merger of $\sim30\,M_\odot$ primordial black holes (PBHs) may provide a significant number of events in gravitational-wave observatories over the next decade, if they make up an appreciable fraction of the dark matter. Here we show that measurement of the eccentricities of the inspiralling binary black holes can be used to distinguish these binaries from those pr…
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It was recently suggested that the merger of $\sim30\,M_\odot$ primordial black holes (PBHs) may provide a significant number of events in gravitational-wave observatories over the next decade, if they make up an appreciable fraction of the dark matter. Here we show that measurement of the eccentricities of the inspiralling binary black holes can be used to distinguish these binaries from those produced by more traditional astrophysical mechanisms. These PBH binaries are formed on highly eccentric orbits and can then merge on timescales that in some cases are years or less, retaining some eccentricity in the last seconds before the merger. This is to be contrasted with massive-stellar-binary, globular-cluster, or other astrophysical origins for binary black holes (BBHs) in which the orbits have very effectively circularized by the time the BBH enters the observable LIGO window. Here we discuss the features of the gravitational-wave signals that indicate this eccentricity and forecast the sensitivity of LIGO and the Einstein Telescope to such effects. We show that if PBHs make up the dark matter, then roughly one event should have a detectable eccentricity given LIGO's expected sensitivity and observing time of six years. The Einstein Telescope should see $O(10)$ such events after ten years.
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Submitted 23 June, 2016;
originally announced June 2016.
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Determining the progenitors of merging black-hole binaries
Authors:
Alvise Raccanelli,
Ely D. Kovetz,
Simeon Bird,
Ilias Cholis,
Julian B. Munoz
Abstract:
We investigate a possible method for determining the progenitors of black hole (BH) mergers observed via their gravitational wave (GW) signal. We argue that measurements of the cross-correlation of the GW events with overlapping galaxy catalogs may provide an additional tool in determining if BH mergers trace the stellar mass of the Universe, as would be expected from mergers of the endpoints of s…
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We investigate a possible method for determining the progenitors of black hole (BH) mergers observed via their gravitational wave (GW) signal. We argue that measurements of the cross-correlation of the GW events with overlapping galaxy catalogs may provide an additional tool in determining if BH mergers trace the stellar mass of the Universe, as would be expected from mergers of the endpoints of stellar evolution. If on the other hand the BHs are of primordial origin, as has been recently suggested, their merging would be preferentially hosted by lower biased objects, and thus have a lower cross-correlation with luminous galaxies. Here we forecast the expected precision of the cross-correlation measurement for current and future GW detectors such as LIGO and the Einstein Telescope. We then predict how well these instruments can distinguish the model that identifies high-mass BH-BH mergers as the merger of primordial black holes that constitute the dark matter in the Universe from more traditional astrophysical sources.
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Submitted 4 May, 2016;
originally announced May 2016.
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Violation of statistical isotropy and homogeneity in the 21-cm power spectrum
Authors:
Maresuke Shiraishi,
Julian B. Muñoz,
Marc Kamionkowski,
Alvise Raccanelli
Abstract:
Most inflationary models predict primordial perturbations to be statistically isotropic and homogeneous. Cosmic microwave background (CMB) observations, however, indicate a possible departure from statistical isotropy in the form of a dipolar power modulation at large angular scales. Alternative models of inflation, beyond the simplest single-field slow-roll models, can generate a small power asym…
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Most inflationary models predict primordial perturbations to be statistically isotropic and homogeneous. Cosmic microwave background (CMB) observations, however, indicate a possible departure from statistical isotropy in the form of a dipolar power modulation at large angular scales. Alternative models of inflation, beyond the simplest single-field slow-roll models, can generate a small power asymmetry, consistent with these observations. Observations of clustering of quasars show, however, agreement with statistical isotropy at much smaller angular scales. Here, we propose to use off-diagonal components of the angular power spectrum of the 21-cm fluctuations during the dark ages to test this power asymmetry. We forecast results for the planned SKA radio array, a future radio array, and the cosmic-variance-limited case as a theoretical proof of principle. Our results show that the 21-cm line power spectrum will enable access to information at very small scales and at different redshift slices, thus improving upon the current CMB constraints by $\sim 2$ orders of magnitude for a dipolar asymmetry and by $\sim 1-3$ orders of magnitude for a quadrupolar asymmetry case.
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Submitted 10 May, 2016; v1 submitted 3 March, 2016;
originally announced March 2016.
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Cosmological Measurements with General Relativistic Galaxy Correlations
Authors:
Alvise Raccanelli,
Francesco Montanari,
Daniele Bertacca,
Olivier Doré,
Ruth Durrer
Abstract:
We investigate the cosmological dependence and the constraining power of large-scale galaxy correlations, including all redshift-distortions, wide-angle, lensing and gravitational potential effects on linear scales. We analyze the cosmological information present in the lensing convergence and in the gravitational potential terms describing the so-called "relativistic effects," and we find that, w…
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We investigate the cosmological dependence and the constraining power of large-scale galaxy correlations, including all redshift-distortions, wide-angle, lensing and gravitational potential effects on linear scales. We analyze the cosmological information present in the lensing convergence and in the gravitational potential terms describing the so-called "relativistic effects," and we find that, while smaller than the information contained in intrinsic galaxy clustering, it is not negligible. We investigate how neglecting them does bias cosmological measurements performed by future spectroscopic and photometric large-scale surveys such as SKA and Euclid. We perform a Fisher analysis using the CLASS code, modified to include scale-dependent galaxy bias and redshift-dependent magnification and evolution bias. Our results show that neglecting relativistic terms introduces an error in the forecasted precision in measuring cosmological parameters of the order of a few tens of percent, in particular when measuring the matter content of the Universe and primordial non-Gaussianity parameters. Therefore, we argue that radial correlations and integrated relativistic terms need to be taken into account when forecasting the constraining power of future large-scale number counts of galaxy surveys.
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Submitted 22 May, 2015;
originally announced May 2015.
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Cosmology on the Largest Scales with the SKA
Authors:
S. Camera,
A. Raccanelli,
P. Bull,
D. Bertacca,
X. Chen,
P. G. Ferreira,
M. Kunz,
R. Maartens,
Y. Mao,
M. G. Santos,
P. R. Shapiro,
M. Viel,
Y. Xu
Abstract:
The study of the Universe on ultra-large scales is one of the major science cases for the Square Kilometre Array (SKA). The SKA will be able to probe a vast volume of the cosmos, thus representing a unique instrument, amongst next-generation cosmological experiments, for scrutinising the Universe's properties on the largest cosmic scales. Probing cosmic structures on extremely large scales will ha…
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The study of the Universe on ultra-large scales is one of the major science cases for the Square Kilometre Array (SKA). The SKA will be able to probe a vast volume of the cosmos, thus representing a unique instrument, amongst next-generation cosmological experiments, for scrutinising the Universe's properties on the largest cosmic scales. Probing cosmic structures on extremely large scales will have many advantages. For instance, the growth of perturbations is well understood for those modes, since it falls fully within the linear regime. Also, such scales are unaffected by the poorly understood feedback of baryonic physics. On ultra-large cosmic scales, two key effects become significant: primordial non-Gaussianity and relativistic corrections to cosmological observables. Moreover, if late-time acceleration is driven not by dark energy but by modifications to general relativity, then such modifications should become apparent near and above the horizon scale. As a result, the SKA is forecast to deliver transformational constraints on non-Gaussianity and to probe gravity on super-horizon scales for the first time.
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Submitted 19 January, 2015; v1 submitted 15 January, 2015;
originally announced January 2015.
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Measuring redshift-space distortions with future SKA surveys
Authors:
Alvise Raccanelli,
Philip Bull,
Stefano Camera,
David Bacon,
Chris Blake,
Olivier Dore,
Pedro Ferreira,
Roy Maartens,
Mario Santos,
Matteo Viel,
Gong-bo Zhao
Abstract:
The peculiar motion of galaxies can be a particularly sensitive probe of gravitational collapse. As such, it can be used to measure the dynamics of dark matter and dark energy as well the nature of the gravitational laws at play on cosmological scales. Peculiar motions manifest themselves as an overall anisotropy in the measured clustering signal as a function of the angle to the line-of-sight, kn…
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The peculiar motion of galaxies can be a particularly sensitive probe of gravitational collapse. As such, it can be used to measure the dynamics of dark matter and dark energy as well the nature of the gravitational laws at play on cosmological scales. Peculiar motions manifest themselves as an overall anisotropy in the measured clustering signal as a function of the angle to the line-of-sight, known as redshift-space distortion (RSD). Limiting factors in this measurement include our ability to model non-linear galaxy motions on small scales and the complexities of galaxy bias. The anisotropy in the measured clustering pattern in redshift-space is also driven by the unknown distance factors at the redshift in question, the Alcock-Paczynski distortion. This weakens growth rate measurements, but permits an extra geometric probe of the Hubble expansion rate. In this chapter we will briefly describe the scientific background to the RSD technique, and forecast the potential of the SKA phase 1 and the SKA2 to measure the growth rate using both galaxy catalogues and intensity mapping, assessing their competitiveness with current and future optical galaxy surveys.
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Submitted 15 January, 2015;
originally announced January 2015.
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Testing foundations of modern cosmology with SKA all-sky surveys
Authors:
Dominik J. Schwarz,
David Bacon,
Song Chen,
Chris Clarkson,
Dragan Huterer,
Martin Kunz,
Roy Maartens,
Alvise Raccanelli,
Matthias Rubart,
Jean-Luc Starck
Abstract:
Continuum and HI surveys with the Square Kilometre Array (SKA) will allow us to probe some of the most fundamental assumptions of modern cosmology, including the Cosmological Principle. SKA all-sky surveys will map an enormous slice of space-time and reveal cosmology at superhorizon scales and redshifts of order unity. We illustrate the potential of these surveys and discuss the prospects to measu…
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Continuum and HI surveys with the Square Kilometre Array (SKA) will allow us to probe some of the most fundamental assumptions of modern cosmology, including the Cosmological Principle. SKA all-sky surveys will map an enormous slice of space-time and reveal cosmology at superhorizon scales and redshifts of order unity. We illustrate the potential of these surveys and discuss the prospects to measure the cosmic radio dipole at high fidelity. We outline several potentially transformational tests of cosmology to be carried out by means of SKA all-sky surveys.
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Submitted 15 January, 2015;
originally announced January 2015.
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Relativistic corrections and non-Gaussianity in radio continuum surveys
Authors:
Roy Maartens,
Gong-Bo Zhao,
David Bacon,
Kazuya Koyama,
Alvise Raccanelli
Abstract:
Forthcoming radio continuum surveys will cover large volumes of the observable Universe and will reach to high redshifts, making them potentially powerful probes of dark energy, modified gravity and non-Gaussianity. Here we extend recent works by analyzing the general relativistic (GR) corrections to the angular power spectrum. These GR corrections to the standard Newtonian analysis of the power s…
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Forthcoming radio continuum surveys will cover large volumes of the observable Universe and will reach to high redshifts, making them potentially powerful probes of dark energy, modified gravity and non-Gaussianity. Here we extend recent works by analyzing the general relativistic (GR) corrections to the angular power spectrum. These GR corrections to the standard Newtonian analysis of the power spectrum become significant on scales near and beyond the Hubble scale at each redshift. We consider the continuum surveys with LOFAR, WSRT and ASKAP, and examples of continuum surveys with the SKA. We find that the GR corrections are at most percent-level in LOFAR, WODAN and EMU surveys, but they can produce $O(10%)$ changes for high enough sensitivity SKA continuum surveys. The signal is however dominated by cosmic variance, and multiple-tracer observations will be needed to overcome this problem. The GR corrections are suppressed in continuum surveys because of the integration over redshift -- we expect that GR corrections will be enhanced for future SKA HI surveys in which the source redshifts will be known. We also provide predictions for the angular power spectra in the case where the primordial perturbations have local non-Gaussianity. We find that non-Gaussianity dominates over GR corrections, and rises above cosmic variance when $f_{\rm NL}\gtrsim5$ for SKA continuum surveys.
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Submitted 24 January, 2013; v1 submitted 4 June, 2012;
originally announced June 2012.
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Beyond the plane-parallel and Newtonian approach: Wide-angle redshift distortions and convergence in general relativity
Authors:
Daniele Bertacca,
Roy Maartens,
Alvise Raccanelli,
Chris Clarkson
Abstract:
We extend previous analyses of wide-angle correlations in the galaxy power spectrum in redshift space to include all general relativistic effects. These general relativistic corrections to the standard approach become important on large scales and at high redshifts, and they lead to new terms in the wide-angle correlations. We show that in principle the new terms can produce corrections of nearly…
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We extend previous analyses of wide-angle correlations in the galaxy power spectrum in redshift space to include all general relativistic effects. These general relativistic corrections to the standard approach become important on large scales and at high redshifts, and they lead to new terms in the wide-angle correlations. We show that in principle the new terms can produce corrections of nearly 10 % on Gpc scales over the usual Newtonian approximation. General relativistic corrections will be important for future large-volume surveys such as SKA and Euclid, although the problem of cosmic variance will present a challenge in observing this.
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Submitted 16 September, 2015; v1 submitted 23 May, 2012;
originally announced May 2012.
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CMB-Galaxy correlation in Unified Dark Matter Scalar Field Cosmologies
Authors:
Daniele Bertacca,
Alvise Raccanelli,
Oliver F. Piattella,
Davide Pietrobon,
Nicola Bartolo,
Sabino Matarrese,
Tommaso Giannantonio
Abstract:
We present an analysis of the cross-correlation between the CMB and the large-scale structure (LSS) of the Universe in Unified Dark Matter (UDM) scalar field cosmologies. We work out the predicted cross-correlation function in UDM models, which depends on the speed of sound of the unified component, and compare it with observations from six galaxy catalogues (NVSS, HEAO, 2MASS, and SDSS main galax…
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We present an analysis of the cross-correlation between the CMB and the large-scale structure (LSS) of the Universe in Unified Dark Matter (UDM) scalar field cosmologies. We work out the predicted cross-correlation function in UDM models, which depends on the speed of sound of the unified component, and compare it with observations from six galaxy catalogues (NVSS, HEAO, 2MASS, and SDSS main galaxies, luminous red galaxies, and quasars). We sample the value of the speed of sound and perform a likelihood analysis, finding that the UDM model is as likely as the LambdaCDM, and is compatible with observations for a range of values of c_\infinity (the value of the sound speed at late times) on which structure formation depends. In particular, we obtain an upper bound of c_\infinity^2 \leq 0.009 at 95% confidence level, meaning that the LambdaCDM model, for which c_\infinity^2 = 0, is a good fit to the data, while the posterior probability distribution peaks at the value c_\infinity^2=10^(-4) . Finally, we study the time dependence of the deviation from LambdaCDM via a tomographic analysis using a mock redshift distribution and we find that the largest deviation is for low-redshift sources, suggesting that future low-z surveys will be best suited to constrain UDM models.
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Submitted 23 March, 2011; v1 submitted 1 February, 2011;
originally announced February 2011.