arXiv subjects

Michele Maggiore

Publications and source records attributed to Michele Maggiore.

At least 37 records · Page 2Linked to original sources

arXiv2022

Gravitational-wave cosmology with dark sirens: state of the art and perspectives for 3G detectors

A joint fit of the mass and redshift distributions of the population of Binary Black Holes detected with Gravitational-Wave observations can be used to obtain constraints on the Hubble parameter and on deviations from General Relativity in the propagation of Gravitational Waves. We first present applications of this technique to the latest catalog of Gravitational-Wave events, focusing on the comparison of different parametrizations for the source-frame mass distribution of Black Hole Binaries. We find that models with more than one feature are favourite by the data, as suggested by population studies, even when varying the cosmology. Then, we discuss perspectives for the use of this technique with third generation Gravitational-Wave detectors, exploiting the recently developed Fisher information matrix Python code GWFAST.

gr-qc↗

arXiv2022

Measuring properties of primordial black hole mergers at cosmological distances: effect of higher order modes in gravitational waves

Primordial black holes (PBHs) may form from the collapse of matter overdensities shortly after the Big Bang. One may identify their existence by observing gravitational wave (GW) emissions from merging PBH binaries at high redshifts $z\gtrsim 30$, where astrophysical binary black holes (BBHs) are unlikely to merge. The next-generation ground-based GW detectors, Cosmic Explorer and Einstein Telescope, will be able to observe BBHs with total masses of $\mathcal{O}(10-100)~M_{\odot}$ at such redshifts. This paper serves as a companion paper of arXiv:2108.07276, focusing on the effect of higher-order modes (HoMs) in the waveform modeling, which may be detectable for these high redshift BBHs, on the estimation of source parameters. We perform Bayesian parameter estimation to obtain the measurement uncertainties with and without HoM modeling in the waveform for sources with different total masses, mass ratios, orbital inclinations and redshifts observed by a network of next-generation GW detectors. We show that including HoMs in the waveform model reduces the uncertainties of redshifts and masses by up to a factor of two, depending on the exact source parameters. We then discuss the implications for identifying PBHs with the improved single-event measurements, and expand the investigation of the model dependence of the relative abundance between the BBH mergers originating from the first stars and the primordial BBH mergers as shown in arXiv:2108.07276.

astro-ph.CO↗

arXiv2022

Forecasting the detection capabilities of third-generation gravitational-wave detectors using $\texttt{GWFAST}$

We introduce $\texttt{GWFAST}$, a novel Fisher-matrix code for gravitational-wave studies, tuned toward third-generation gravitational-wave detectors such as Einstein Telescope (ET) and Cosmic Explorer (CE). We use it to perform a comprehensive study of the capabilities of ET alone, and of a network made by ET and two CE detectors, as well as to provide forecasts for the forthcoming O4 run of the LVK collaboration. We consider binary neutron stars, binary black holes and neutron star-black hole binaries, and compute basic metrics such as the distribution of signal-to-noise ratio (SNR), the accuracy in the reconstruction of various parameters (including distance, sky localization, masses, spins and, for neutron stars, tidal deformabilities), and the redshift distribution of the detections for different thresholds in SNR and different levels of accuracy in localization and distance measurement. We examine the expected distribution and properties of `golden events', with especially large values of the SNR. We also pay special attention to the dependence of the results on astrophysical uncertainties and on various technical details (such as choice of waveforms, or the threshold in SNR), and we compare with other Fisher codes in the literature. In a companion paper we discuss the technical aspects of the code. Together with this paper, we publicly release the code $\texttt{GWFAST}$ at https://github.com/CosmoStatGW/gwfast, and the library $\texttt{WF4Py}$ implementing state-of-the-art gravitational-wave waveforms in pure $\texttt{Python}$ at https://github.com/CosmoStatGW/WF4Py.

gr-qc↗

arXiv2022

$\texttt{GWFAST}$: a Fisher information matrix Python code for third-generation gravitational-wave detectors

We introduce $\texttt{GWFAST}$, a Fisher information matrix $\texttt{Python}$ code that allows easy and efficient estimation of signal-to-noise ratios and parameter measurement errors for large catalogs of resolved sources observed by networks of gravitational-wave detectors. In particular, $\texttt{GWFAST}$ includes the effects of the Earth's motion during the evolution of the signal, supports parallel computation, and relies on automatic differentiation rather than on finite differences techniques, which allows the computation of derivatives with accuracy close to machine precision. We also release the library $\texttt{WF4Py}$ implementing state-of-the-art gravitational-wave waveforms in $\texttt{Python}$. In this paper we provide a documentation of $\texttt{GWFAST}$ and $\texttt{WF4Py}$ with practical examples and tests of performance and reliability. In a companion paper we present forecasts for the detection capabilities of the second and third generation of ground-based gravitational-wave detectors, obtained with $\texttt{GWFAST}$.

astro-ph.IM↗

arXiv2022

New Horizons for Fundamental Physics with LISA

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.

gr-qc↗

arXiv2022

Cosmology with the Laser Interferometer Space Antenna

The Laser Interferometer Space Antenna (LISA) has two scientific objectives of cosmological focus: to probe the expansion rate of the universe, and to understand stochastic gravitational-wave backgrounds and their implications for early universe and particle physics, from the MeV to the Planck scale. However, the range of potential cosmological applications of gravitational wave observations extends well beyond these two objectives. This publication presents a summary of the state of the art in LISA cosmology, theory and methods, and identifies new opportunities to use gravitational wave observations by LISA to probe the universe.

astro-ph.CO↗

arXiv2022

Modified gravitational wave propagation: information from strongly lensed binaries and the BNS mass function

Modified gravitational wave propagation is a smoking gun of modifications of gravity at cosmological scales, and can be the most promising observable for testing such theories. The observation of gravitational waves (GW) in recent years has allowed us to start probing this effect, and here we briefly review two promising ways of testing it. We will show that, already with the current network of detectors, it is possible to reach an interesting accuracy in the estimation of the $Ξ_0$ parameter (that characterizes modified gravitational wave propagation, with $Ξ_{0, {\rm GR}} = 1$) and with next generation facilities, such as the Einstein Telescope, we can get a sub-percent measurement.

gr-qc↗

arXiv2022

Cosmology and modified gravity with dark sirens from GWTC-3

We present the latest measurements of the Hubble parameter and of the parameter $Ξ_0$ describing modified gravitational wave propagation, obtained from the third gravitational wave transient catalog, GWTC-3, using the correlation with galaxy catalogs and information from the source-frame mass distribution of binary black holes. The latter leads to the tightest bound on $Ξ_0$ so far, i.e. $Ξ_0 = 1.2^{+0.7}_{-0.7}$ with a flat prior on $Ξ_0$, and $Ξ_0 = 1.0^{+0.4}_{-0.8}$ with a prior uniform in $\logΞ_0$ (Max posterior and $68\%$ HDI). The measurement of $H_0$ is dominated by the single bright siren GW170817, resulting in $H_0=67^{+9}_{-6} \, \rm km \, s^{-1} \, Mpc$ when combined with the galaxy catalog.

gr-qc↗

arXiv2022

Cosmology and modified gravitational wave propagation from binary black hole population models

A joint hierarchical Bayesian analysis of the binary black hole (BBH) mass function, merger rate evolution and cosmological parameters can be used to extract information on both the cosmological and population parameters. We extend this technique to include the effect of modified gravitational wave (GW) propagation. We discuss the constraints on the parameter $Ξ_0$ that describes this phenomenon (with $Ξ_0=1$ in General Relativity, GR) using the data from the GWTC-3 catalog. We find the constraints $Ξ_0 = 1.2^{+0.7}_{-0.7}$ with a flat prior on $Ξ_0$, and $Ξ_0 = 1.0^{+0.4}_{-0.8}$ with a prior uniform in $\logΞ_0$ ($68\%$ C.L., maximum posterior and HDI), which only rely on the presence of a feature in the BBH mass distribution around $\sim 30-45 M_{\odot}$, and are robust to whether or not the event GW190521 is considered an outlier of the population. We then study in more detail the effects of modified GW propagation on population and cosmological analyses for LIGO/Virgo at design sensitivity. For a given data-taking period, the relative error $ΔΞ_0/Ξ_0$ has a significant dependence on the fiducial value of $Ξ_0$, since the latter has a strong influence on the detection rate. For five years of data, the accuracy ranges from $\sim 10\%$ on $Ξ_0$ when $Ξ_0=1$ to $ΔΞ_0/Ξ_0\sim 20\%$ for $Ξ_0=1.8$ - a large deviation from GR, still consistent with current limits and predicted by viable cosmological models. For the Hubble parameter, we forecast an accuracy of $ΔH_0/H_0 \sim 20\%$, and an accuracy on $H(z)$ of $\sim7\%$ at a pivot redshift $z_*\sim 0.8$. We finally show that, if Nature is described by a modified gravity theory with a large deviation from the GR value $Ξ_0=1$, such as $Ξ_0=1.8$, analysing the data assuming GR produces a significant bias in the inferred values of the mass scales, Hubble constant, and BBH merger rate.

gr-qc↗

arXiv2022

Modified gravitational wave propagation and the binary neutron star mass function

Modified gravitational wave (GW) propagation is a generic phenomenon in modified gravity. It affects the reconstruction of the redshift of coalescing binaries from the luminosity distance measured by GW detectors, and therefore the reconstruction of the actual masses of the component compact stars from the observed (`detector-frame') masses. We show that, thanks to the narrowness of the mass distribution of binary neutron stars, this effect can provide a clear signature of modified gravity, particularly for the redshifts explored by third generation GW detectors such as Einstein Telescope and Cosmic Explorer.

gr-qc↗

arXiv2021

Revisiting the algebraic structure of the generalized uncertainty principle

We compare different formulations of the generalized uncertainty principle that have an underlying algebraic structure. We show that the formulation by Kempf, Mangano and Mann (KMM) [Phys. Rev. D 52 (1995)], quite popular for phenomenological studies, satisfies the Jacobi identities only for spin zero particles. In contrast, the formulation proposed earlier by one of us (MM) [Phys. Lett. B 319 (1993)] has an underlying algebraic structure valid for particles of all spins, and is in this sense more fundamental. The latter is also much more constrained, resulting into only two possible solutions, one expressing the existence of a minimum length, and the other expressing a form of quantum-to-classical transition. We also discuss how this more stringent algebraic formulation has an intriguing physical interpretation in terms of a discretized time at the Planck scale.

quant-ph↗

arXiv2021

The Next Generation Global Gravitational Wave Observatory: The Science Book

The next generation of ground-based gravitational-wave detectors will observe coalescences of black holes and neutron stars throughout the cosmos, thousands of them with exceptional fidelity. The Science Book is the result of a 3-year effort to study the science capabilities of networks of next generation detectors. Such networks would make it possible to address unsolved problems in numerous areas of physics and astronomy, from Cosmology to Beyond the Standard Model of particle physics, and how they could provide insights into workings of strongly gravitating systems, astrophysics of compact objects and the nature of dense matter. It is inevitable that observatories of such depth and finesse will make new discoveries inaccessible to other windows of observation. In addition to laying out the rich science potential of the next generation of detectors, this report provides specific science targets in five different areas in physics and astronomy and the sensitivity requirements to accomplish those science goals. This report is the second in a six part series of reports by the GWIC 3G Subcommittee: i) Expanding the Reach of Gravitational Wave Observatories to the Edge of the Universe, ii) The Next Generation Global Gravitational Wave Observatory: The Science Book (this report), iii) 3G R&D: R&D for the Next Generation of Ground-based Gravitational Wave Detectors, iv) Gravitational Wave Data Analysis: Computing Challenges in the 3G Era, v) Future Ground-based Gravitational-wave Observatories: Synergies with Other Scientific Communities, and vi) An Exploration of Possible Governance Models for the Future Global Gravitational-Wave Observatory Network.

gr-qc↗

arXiv2021

On the single-event-based identification of primordial black hole mergers at cosmological distances

The existence of primordial black holes (PBHs), which may form from the collapse of matter overdensities shortly after the Big Bang, is still under debate. Among the potential signatures of PBHs are gravitational waves (GWs) emitted from binary black hole (BBH) mergers at redshifts $z\gtrsim 30$, where the formation of astrophysical black holes is unlikely. Future ground-based GW detectors, Cosmic Explorer and Einstein Telescope, will be able to observe equal-mass BBH mergers with total mass of $\mathcal{O}(10-100)~M_{\odot}$ at such distances. In this work, we investigate whether the redshift measurement of a single BBH source can be precise enough to establish its primordial origin. We simulate BBHs of different masses, mass ratios and orbital orientations. We show that for BBHs with total masses between $20~M_{\odot}$ and $40~M_{\odot}$ merging at $z \geq 40$ one can infer $z>30$ at up to 97\% credibility, with a network of one Einstein Telescope, one 40-km Cosmic Explorer in the US and one 20-km Cosmic Explorer in Australia. A smaller network made of one Einstein Telescope and one 40-km Cosmic Explorer in the US measures $z>30$ at larger than 90\% credibility for roughly half of the sources than the larger network. We then assess the dependence of this result on the Bayesian redshift priors used for the analysis, specifically on the relative abundance of the BBH mergers originated from the first stars, and the primordial BBH mergers.

astro-ph.CO↗

arXiv2021

Cosmology with LIGO/Virgo dark sirens: Hubble parameter and modified gravitational wave propagation

We present a detailed study of the methodology for correlating `dark sirens' (compact binaries coalescences without electromagnetic counterpart) with galaxy catalogs. We propose several improvements on the current state of the art, and we apply them to the GWTC-2 catalog of LIGO/Virgo gravitational wave (GW) detections, and the GLADE galaxy catalog, performing a detailed study of several sources of systematic errors that, with the expected increase in statistics, will eventually become the dominant limitation. We provide a measurement of $H_0$ from dark sirens alone, finding as the best result $H_0=67.3^{+27.6}_{-17.9}\,\,{\rm km}\, {\rm s}^{-1}\, {\rm Mpc}^{-1}$ ($68\%$ c.l.) which is, currently, the most stringent constraint obtained using only dark sirens. Combining dark sirens with the counterpart for GW170817 we find $H_0= 72.2^{+13.9}_{-7.5} \,{\rm km}\, {\rm s}^{-1}\, {\rm Mpc}^{-1}$. We also study modified GW propagation, which is a smoking gun of dark energy and modifications of gravity at cosmological scales, and we show that current observations of dark sirens already start to provide interesting limits. From dark sirens alone, our best result for the parameter $Ξ_0$ that measures deviations from GR (with $Ξ_0=1$ in GR) is $Ξ_0=2.1^{+3.2}_{-1.2}$. We finally discuss limits on modified GW propagation under the tentative identification of the flare ZTF19abanrhr as the electromagnetic counterpart of the binary black hole coalescence GW190521, in which case our most stringent result is $Ξ_0=1.8^{+0.9}_{-0.6}$. We release the publicly available code $\tt{DarkSirensStat}$, which is available under open source license at \url{https://github.com/CosmoStatGW/DarkSirensStat}.

astro-ph.CO↗

arXiv2021

Probing modified gravitational wave propagation with strongly lensed coalescing binaries

It has been recently shown that quadruply lensed gravitational-wave (GW) events due to coalescing binaries can be localized to one or just a few galaxies, even in the absence of an electromagnetic counterpart. We discuss how this can be used to extract information on modified GW propagation, which is a crucial signature of modifications of gravity at cosmological scales. We show that, using quadruply lensed systems, it is possible to constrain the parameter $Ξ_0$ that characterizes modified GW propagation, without the need of imposing a prior on $H_0$. A LIGO/Virgo/Kagra network at target sensitivity might already get a significant measurement of $Ξ_0$, while a third generation GW detector such as the Einstein Telescope could reach a very interesting accuracy.

gr-qc↗

arXiv2021

Absorption spectroscopy of quantum black holes with gravitational waves

The observation of electromagnetic radiation emitted or absorbed by matter was instrumental in revealing the quantum properties of atoms and molecules in the early XX century, and constituted a turning-point in the development of the quantum theory. Quantum mechanics changes dramatically the way radiation and matter interact, making the probability of emission and absorption of light strongly frequency dependent, as clearly manifested in atomic spectra. In this essay, we advocate that gravitational radiation can play, for the quantum aspects of black holes, a similar role as electromagnetic radiation did for atoms, and that the advent of gravitational-wave astronomy can bring this fascinating possibility to the realm of observations.

gr-qc↗

arXiv2021

Potential gravitational-wave signatures of quantum gravity

We show that gravitational-wave astronomy has the potential to inform us on quantum aspects of black holes. Based on Bekenstein's quantization, we find that black hole area discretization could impart observable imprints to the gravitational-wave signal from a pair of merging black holes, affecting their absorption properties during inspiral and their late-time relaxation after merger. In contrast with previous results, we find that black hole rotation, ubiquitous in astrophysics, improves our ability to probe quantum effects. Our analysis shows that gravitational-wave echoes and suppressed tidal heating are signs of new physics from which the fundamental quantum of black hole area can be measured, and which are within reach of future detectors. Our results also highlight the need to derive predictions from specific quantum gravity proposals.

gr-qc↗

arXiv2020

Science Case for the Einstein Telescope

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.

astro-ph.CO↗