Primordial black holes (PBHs) might be formed in the early Universe and could comprise at least a fraction of the dark matter. Using the recently released GWTC-2 dataset from the third observing run of the LIGO-Virgo Collaboration, we investigate whether current observations are compatible with the hypothesis that all black hole mergers detected so far are of primordial origin. We constrain PBH formation models within a hierarchical Bayesian inference framework based on deep learning techniques, finding best-fit values for distinctive features of these models, including the PBH initial mass function, the fraction of PBHs in dark matter, and the accretion efficiency. The presence of several spinning binaries in the GWTC-2 dataset favors a scenario in which PBHs accrete and spin up. Our results indicate that PBHs may comprise only a fraction smaller than $0.3 \%$ of the total dark matter, and that the predicted PBH abundance is still compatible with other constraints.
We perform a hierarchical Bayesian analysis of the GWTC-2 catalog to investigate the mixed scenario in which the merger events are explained by black holes of both astrophysical and primordial origin. For the astrophysical scenario we adopt the phenomenological model used by the LIGO/Virgo collaboration and we include the correlation between different parameters inferred from data, the role of the spins in both the primordial and astrophysical scenarios, and the impact of accretion in the primordial scenario. Our best-fit mixed model has a strong statistical evidence relative to the single-pop…
The discovery of gravitational waves (GWs) provides an unprecedented arena to test general relativity, including the gravitational Lorentz invariance violation (gLIV). In the propagation of GWs, a generic gLIV leads to anisotropy, dispersion, and birefringence. GW events constrain the anisotropic birefringence particularly well. Kostelecký and Mewes (2016) performed a preliminary analysis for GW150914. We improve their method and extend the analysis systematically to the whole GW transient catalog, GWTC-1. This is the first global analysis of the spacetime anisotropic Lorentzian structure with…
The study of current gravitational waves (GW) catalogues provide an interesting model independent way to understand further the nature of dark energy. In this work, we present an update of the constrains related to dynamical dark energy parametrisations using recent Gravitational-Wave Transient catalogues (GWTC-1 and GWTC-2) along with Type Ia supernova (SNeIa) and Cosmic Chronometers (CC) catalogues. According to our Bayesian results using the full SNeIa+CC+GW database, the $Λ$CDM model shows a strong preference against two dark energy parameterisation known as Barboza-Alcaniz (BA) and the Lo…
In this paper, we revisit the problem of using gravitational wave data to test the Einstein-dilation-Gauss-Bonnet theory, by using nine selected gravitational wave events from GWTC-3. Compared with existing work, we are taking into account the higher harmonics more properly and we also study the contribution of the merger-ringdown data. Using the inspiral data alone, we find that the best result is from GW200115, giving $\sqrt{|α|} < 1.1$ km, which is about 17\% tighter than the previous best result. We also notice the possible existence of a simple unexpected relation among the constraints fr…
We present a flexible model to describe the effects of generic deviations of observed gravitational wave signals from modeled waveforms in the LIGO and Virgo gravitational wave detectors. With the detection of 11 gravitational wave events from the GWTC-1 catalog, we are able to constrain possible deviations from our modeled waveforms. In this paper we present our coherent spline model that describes the deviations, then choose to validate our model on an example phenomenological and astrophysically motivated departure in waveforms based on extreme spontaneous scalarization. We find that the mo…
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 …
Parameter estimation for the GWTC-4.0 catalog with phenomenological waveform models that include orbital eccentricity and an updated description of spin precession
Universitat de les Illes Balears（巴利阿里群岛大学）；Institut de Ciències de l’Espai (ICE, CSIC)（空间科学研究所）
We perform a new test of general relativity (GR) with signals from GWTC-2, the LIGO and Virgo catalog of gravitational wave detections. We search for the presence of amplitude birefringence, in which left versus right circularly polarized modes of gravitational waves are exponentially enhanced and suppressed during propagation. Such an effect is present in various beyond-GR theories but is absent in GR. We constrain the amount of amplitude birefringence consistent with the data through an opacity parameter $κ$, which we bound to be $κ\lesssim 0.74 \textrm{ Gpc}^{-1}$. We then use these theory-…
The weak equivalence principle (WEP) is the cornerstone of gravitational theories. At the local scale, WEP has been tested to high accuracy by various experiments. On the intergalactic distance scale, WEP could be tested by comparing the arrival time of different messengers emitted from the same source. The gravitational time delay caused by massive galaxies is proportional to $γ+1$, where the parameter $γ$ is unity in general relativity. The values of $γ$ for different massless particles should be different if WEP is violated, i.e., $Δγ$ is used to indicate the deviation from WEP. So far, $|Δ…
The propagation of gravitational waves can reveal fundamental features of the structure of spacetime. For instance, differences in the propagation of gravitational-wave polarizations would be a smoking gun for parity violations in the gravitational sector, as expected from birefringent theories like Chern-Simons gravity. Here we look for evidence of amplitude birefringence in the third catalog of detections by the Laser Interferometer Gravitational Wave Observatory and Virgo through the use of birefringent templates inspired by dynamical Chern-Simons gravity. From $71$ binary-black-hole signal…
A discovery of gravitational waves from binary black holes raises a possibility that measurements of them can provide strict tests of CPT invariance in gravitational waves. When CPT violation exists, if any, gravitational waves with different circular polarizations could gain a slight difference in propagating speeds. Hence, the birefringence of gravitational waves is induced and there should be a rotation of plus and cross modes. For CPT-violating dispersion relation ${ω^{2}=k^{2}}$ ${\pm 2ζk^{3}}$, where a sign ${\pm}$ denotes different circular polarizations, we find no substantial deviatio…
The data analysis carried out by the LIGO-Virgo collaboration on gravitational-wave events utilizes nested sampling to compute Bayesian evidences and posterior distributions for inferring the source properties of compact binaries. With poor sampling from the constrained prior, nested sampling algorithms may misbehave and fail to sample the posterior distribution faithfully. Fowlie et al. (2020) outlines a method of validating the performance of nested sampling, or identifying pathologies such as plateaus in the parameter space, using likelihood insertion order statistics. Here, this method is …
In the first Gravitational-Wave Transient Catalogue of LIGO and Virgo, all events are announced having zero eccentricity. In the present paper, we investigate the performance of SEOBNRE which is a spin-aligned eccentric waveform model in time-domain. By comparing with all the eccentric waveforms in SXS library, we find that the SEOBNRE coincides perfectly with numerical relativity data. Employing the SEOBNRE, we re-estimate the eccentricities of all black hole merger events. We find that most of these events allow a possibility for existence of initial eccentricities at 10 Hz band, but are tot…
Gravitational-wave astronomy offers not only new vistas into the realm of astrophysics, but it also opens an avenue for probing, for the first time, general relativity in its strong-field, nonlinear, and dynamical regime, where the theory's predictions manifest themselves in their full glory. We present a study of whether the gravitational wave events detected so far by the LIGO-Virgo scientific collaborations can be used to probe higher-curvature corrections to general relativity. In particular, we focus on two examples: Einstein-dilaton-Gauss-Bonnet and dynamical Chern-Simons gravity. We fin…
We summarize the four tests of general relativity carried out using the ten binary black hole signals detected by Advanced LIGO and Advanced Virgo and included in their first catalog, GWTC-1. These events provide unprecedented opportunities for testing the predictions of general relativity for the gravitational waveforms from these highly dynamical, strong-field events. The first two tests check the consistency of the residuals with noise and the consistency of the low- and high-frequency parts of the signal. The other two tests check that parameterized deviations in the waveform model---inclu…
We have examined gravitational wave echo signals for nine binary black hole merger events observed by Advanced LIGO and Virgo during the first and second observation runs. To construct an echo template, we consider Kerr spacetime, where the event horizon is replaced by a reflective membrane. We use frequency-dependent reflection rate at the angular potential barrier, which is fitted to the numerical data obtained by solving Teukolsky equations. This reflection rate gives a frequency-dependent transmission rate that is suppressed at lower frequencies in the template. We also take into account t…
In modified gravity models that allow for additional non-compact spacetime dimensions, energy from gravitational waves can leak into these extra spacetime dimensions, leading to a reduction in the amplitude of the observed gravitational waves, and thus a source of potential systematics in the inferred luminosity distances to gravitational wave sources. Since binary black hole (BBH) mergers are standard sirens, we use the pair-instability supernova (PISNe) mass gap and its predicted features to determine a mass scale and thus be able to break the mass-redshift degeneracy. We simultaneously fit …
Gravitational-wave (GW) catalogs are rapidly increasing in number, allowing for robust statistical analyses of the population of compact binaries. Nonetheless, GW inference of cosmology has typically relied on additional electromagnetic counterparts or galaxy catalogs. I present a new probe of cosmological modifications of general relativity with GW data only. I focus on deviations of the GW luminosity distance constrained with the astrophysical population of binary black holes (BBHs). The three key observables are 1) the number of events as a function of luminosity distance, 2) the stochastic…
The LIGO--Virgo--KAGRA collaborations (LVK) produced a catalogue containing gravitational-wave (GW) observations from the first half of the third GW observing run (O3a). This catalogue, GWTC-2.1, includes for the first time a number of \emph{exceptional} GW candidates produced from merging black-hole-binaries with unequivocally unequal component masses. Since subdominant multipole moments and spin-induced orbital precession are more likely to leave measurable imprints on the emitted GW from unequal component mass binaries, these general relativistic phenomena may now be measurable. Indeed, bot…
The Advanced LIGO and Virgo detectors opened a new era to study black holes (BHs) in our Universe. A population of stellar-mass binary BHs (BBHs) are discovered to be heavier than previously expected. These heavy BBHs provide us an opportunity to achieve multiband observation with ground-based and space-based gravitational-wave (GW) detectors. In this work, we use BBHs discovered by the LIGO/Virgo Collaboration as indubitable examples, and study in great detail the prospects for multiband observation with GW detectors in the near future. We apply the Fisher matrix to spinning, non-precessing i…
It is expected that the orbital planes of gravitational-wave (GW) sources are isotropically distributed. However, both physical and technical factors, such as alternate theories of gravity with birefringence, catalog contamination, and search algorithm limitations, could result in inferring a non-isotropic distribution. Showing that the inferred astrophysical distribution of the orbital orientations is indeed isotropic can thus be used to rule out some violations of general relativity, as a null test about the purity of the GW catalog sample, and as a check that selection effects are being pro…
A stepping stone toward detecting gravitational wave memory: a cumulative analysis with the full $(\ell=2, m=0)$ spherical harmonic using events from GWTC-4.0 and GWTC-5.0
Universitat de les Illes Balears（巴利阿里群岛大学）；Institut de Ciències de l’Espai (ICE, CSIC)（空间科学研究所）
Successful detection of gravitational waves has presented a new avenue to explore the nature of gravity. With the cumulative catalog of detected events, we can perform tests on General Relativity from various aspects with increasing precision. In this work, we focus on Lorentz symmetry during propagation of gravitational waves. Considering the dispersion relation in the gauge-invariant linearized gravity sector of the Standard-Model Extension, the anisotropy, birefringence, and dispersion effects will be induced during propagation of gravitational waves because of the Lorentz violating modific…
Testing black hole's charged property is a fascinating topic in modified gravity and black hole astrophysics. In the first Gravitational-Wave Transient Catalog (GWTC-1), ten binary black hole merger events have been formally reported, and these gravitational wave signals have significantly enhanced our understanding of the black hole. In this paper, we try to constrain the amount of electric charge with the parameterized post-Einsteinian framework by treating the electric charge as a small perturbation in a Bayesian way. We find that the current limits in our work are consistent with the resul…
Observations of gravitational waves (GWs) by the advanced LIGO--Virgo detectors provide us with ground breaking opportunities to test predictions of Einstein's theory of general relativity (GR) in the strong field regime. In this article, we summarise the nine tests of GR performed on the new GW signals included in the third GW transient catalog, GWTC-3. These tests include overall and self-consistency checks of the signal with the data; tests of the GW generation, propagation and polarizations; and probes of the nature of the remnant object by testing the BH ringdown hypothesis and searching …
Constraining the gravitational-wave breathing mode with LVK antenna patterns and GWTC data
National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；The International Centre for Theoretical Physics Asia-Pacific, University of Chinese Academy of Sciences（亚洲太平洋理论物理中心，中国科学院大学）；Missouri University of Science and Technology（密苏里科技大学）
Black hole thermodynamics has brought strong hints of a profound and fundamental connection between gravity, thermodynamics, and quantum theory. If the black hole does behave like a natural thermodynamic system, it should be thermodynamically stable in a clean environment. In this paper, using the observational data of binary black hole (BBH) mergers observed by LIGO, Virgo, and KAGRA detectors, we check whether the black hole remnants produced from BBH mergers in the LIGO-Virgo-KAGRA catalog GWTC-3 are thermodynamically stable. The criterion for the thermodynamic stability is quite simple and…
We consider the ten confidently detected gravitational-wave signals in the GWTC-1 catalog which are consistent with mergers of binary black hole systems, and perform a thorough parameter estimation re-analysis. This is made possible by using computationally efficient waveform models of the current (fourth) generation of the IMRPhenom family of phenomenological waveform models, which consists of the IMRPhenomX frequency-domain modelsand the IMRPhenomT time-domain models. The analysis is performed with both precessing and non-precessing waveform models with and without subdominant spherical harm…
Searching for Extra Dimensions with Gravitational Waves: Dark-Siren Constraints from GWTC-4
International Center for Theoretical Physics Asia-Pacific, University of Chinese Academy of Sciences（国际理论物理中心亚太区，中国科学院大学）；Taiji Laboratory for Gravitational Wave Universe, University of Chinese Academy of Sciences（太极引力波宇宙实验室，中国科学院大学）
Mind the peak: improving cosmological constraints from GWTC-4.0 spectral sirens using semiparametric mass models
Università di Bologna（博洛尼亚大学）；INAF - Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（博洛尼亚天文物理与空间科学研究所）；INFN - Sezione di Bologna（博洛尼亚意大利国家核物理研究所）
Constraining Ultralight Scalars with Black Hole Binary Mergers in Galactic Nuclei
Racah Institute of Physics, Hebrew University of Jerusalem（雷卡物理研究所，耶路撒冷希伯来大学）；Department of Astronomy, University of Wisconsin, Madison（威斯康星大学麦迪逊分校天文学系）
We carry out astrophysical inference for compact binary merger events in LIGO-Virgo's first gravitational-wave transient catalog (GWTC-1) using a physically motivated calibration model. We demonstrate that importance sampling can be used to reduce the cost of what would otherwise be a computationally challenging analysis. We show that including the physical estimate for the calibration error distribution has negligible impact on the inference of parameters for the events in GWTC-1. Studying a simulated signal with matched filter signal-to-noise ratio $\text{SNR}=200$, we project that a calibra…
Parity-violating (PV) gravity has recently attracted interest in several aspects. One of them is the axion-graviton coupling to test the axion-dark matter model. Moreover, by extending Chern-Simons (CS) gravity to include derivatives of a scalar field up to the second order, a more general class of PV gravity theory, which we call the CNCL model, has been proposed~[M. Crisostomi {\it et al.}, Phys. Rev. D, {\bf 97}, 044034 (2018)]. The model can be further extended by including even higher derivatives of the scalar field and/or higher curvature terms. In this paper, we discuss the effect of pa…
We show that the gravitational waves measurements have raised the opportunity to measure $H_0$ with dark sirens to within 2$σ$, the accuracy required to resolve the \hubble tension. There are two principal reasons for our results: (1) upgrades to GW LIGO-Virgo transient catalogues GWTC-1 and GWTC-2 enhance their sensitive with only 10\% of contamination fraction, and (2) new dark sirens should help to constrain our dynamical EoS. In conjunction, sensitivity upgrades and a new dark energy model will facilitate an accurate inference of the \hubble constant $H_0$ to better with an $\pm 0.077$ err…
In this paper, we investigate the morphology of the events from the GWTC-1 catalog of compact binary coalescences as reconstructed by a method based on coherent excess power: we use an open-source version of the coherent WaveBurst (cWB) analysis pipeline, which does not make use of waveform models. The coherent response of the LIGO-Virgo network of detectors is estimated by using loose bounds on the duration and bandwidth of the signal. This pipeline version reproduces the same results that are reported for cWB in recent publications by the LIGO and Virgo collaborations. In particular, the sky…
Lorentz invariance plays a fundamental role in modern physics. However, tiny violations of the Lorentz invariance may arise in some candidate quantum gravity theories. Prominent signatures of the gravitational Lorentz invariance violation (gLIV) include anisotropy, dispersion, and birefringence in the dispersion relation of gravitational waves (GWs). Using a total of 50 GW events in the GW transient catalogs GWTC-1 and GWTC-2, we perform an analysis on the anisotropic birefringence phenomenon. The use of multiple events allows us to completely break the degeneracy among gLIV coefficients and g…
Constraining the Hubble Constant using Cross-Correlation of Gravitational Wave Events with Flux-Limited Galaxy Catalog
Institute for Cosmic Ray Research, The University of Tokyo（宇宙射线研究所，东京大学）；Inter-University Centre for Astronomy and Astrophysics（天文与天体物理跨大学中心）；Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo（汤川秀树物理数学宇宙研究所（WPI），东京大学）
As a candidate bound for the Binary Black Hole (BBH) merger events detected by LIGO/Virgo, Primordial Black Holes (PBHs) provide a useful tool to investigate the primordial curvature perturbations on small scales. Using the GWTC-1 to GWTC-3 catalogs, under the scenario that PBHs originate from large primordial curvature perturbations on small scales during inflationary epoch, we for the first time reconstruct the power spectrum of primordial curvature perturbations on small scales. It is found that the value of the amplitude of the primordial power spectrum is enhanced to $\mathcal{O}(10^{-2})…
