1,721,139 research outputs found
Inference of cosmological parameters from gravitational waves: Applications to second generation interferometers
No full textThe advanced worldwide network of gravitational waves (GW) observatories is scheduled to begin operations within the current decade. Thanks to their improved sensitivity, they promise to yield a number of detections and thus to open new observational windows for astronomy and astrophysics. Among the scientific goals that should be achieved, there is the independent measurement of the value of the cosmological parameters, hence an independent test of the current cosmological paradigm. Because of the importance of such a task, a number of studies have evaluated the capabilities of GW telescopes in this respect. However, since GW do not yield information about the source redshift, different groups have made different assumptions regarding the means through which the GW redshift can be obtained. These different assumptions imply also different methodologies to solve this inference problem. This work presents a formalism based on Bayesian inference developed to facilitate the inclusion of all assumptions and prior information about a GW source within a single data analysis framework. This approach guarantees the minimization of information loss and the possibility of including naturally event-specific knowledge (such as the sky position for a gamma ray burst-GW coincident observation) in the analysis. The workings of the method are applied to a specific example, loosely designed along the lines of the method proposed by Schutz in 1986, in which one uses information from wide-field galaxy surveys as prior information for the location of a GW source. I show that combining the results from few tens of observations from a network of advanced interferometers will constrain the Hubble constant H 0 to an accuracy of ∼4%-5% at 95% confidence. © 2012 American Physical Society
Observational black hole spectroscopy: a time-domain multimode analysis of GW150914
Full text linkThe detection of the least damped quasinormal mode from the remnant of the gravitational wave event GW150914 realized the long-sought possibility of observationally studying the properties of quasistationary black hole spacetimes through gravitational waves. Past literature has extensively explored this possibility, and the emerging field has been named “black hole spectroscopy.” In this study, we present results regarding the ringdown spectrum of GW150914, obtained by application of Bayesian inference to identify and characterize the ringdown modes. We employ a pure time-domain analysis method, which infers from the data the time of transition between the nonlinear and quasilinear regimes of the postmerger emission in concert with all other parameters characterizing the source. We find that the data provide no evidence for the presence of more than one quasinormal mode. However, from the central frequency and damping time posteriors alone, no unambiguous identification of a single mode is possible. More in-depth analysis adopting a ringdown model based on results in perturbation theory over the Kerr metric confirms that the data do not provide enough evidence to discriminate among an l = 2 and the l = 3 subset of modes. Our work provides the first comprehensive agnostic framework to observationally investigate astrophysical black holes’ ringdown spectra
Erratum: Observational black hole spectroscopy: A time-domain multimode analysis of GW150914 [Phys. Rev. D 99 , 123029 (2019)]
No full text(H)DPGMM: a hierarchy of Dirichlet process Gaussian mixture models for the inference of the black hole mass function
No full textWe introduce (H)DPGMM, a hierarchical Bayesian non-parametric method based on the Dirichlet process Gaussian mixture model, designed to infer data-driven population properties of astrophysical objects without being committal to any specific physical model. We investigate the efficacy of our model on simulated data sets and demonstrate its capability to reconstruct correctly a variety of population models without the need of fine-tuning of the algorithm. We apply our method to the problem of inferring the black hole mass function given a set of gravitational wave observations from LIGO and Virgo, and find that the (H)DPGMM infers a binary black hole mass function that is consistent with previous estimates without the requirement of a theoretically motivated parametric model. Although the number of systems observed is still too small for a robust inference, (H)DPGMM confirms the presence of at least two distinct modes in the observed merging black hole mass function, hence suggesting in a model-independent fashion the presence of at least two classes of binary black hole systems
Quantum black hole spectroscopy: probing the quantum nature of the black hole area using LIGO-Virgo ringdown detections
Full text linkWe present a thorough observational investigation of the heuristic quantised ringdown model presented in [FOIT-KLEBAN (2019)]. This model is based on the Bekenstein-Mukhanov conjecture, stating that the area of a black hole horizon is an integer multiple of the Planck area~ multiplied by a phenomenological constant, α, which can be viewed as an additional black hole intrinsic parameter. Our approach is based on a time-domain analysis of the gravitational wave signals produced by the ringdown phase of binary black hole mergers detected by the LIGO and Virgo collaboration. Employing a full Bayesian formalism and taking into account the complete correlation structure among the black hole parameters, we show that the value of α cannot be constrained using only GW150914, in contrast to what was suggested in [FOIT-KLEBAN (2019)]. We proceed to repeat the same analysis on the new gravitational wave events detected by the LIGO and Virgo Collaboration up to 1 October 2019, obtaining a combined-event measure equal to and a combined log odds ratio of , implying that current data are not informative enough to favour or discard this model against general relativity. We then show that using a population of GW150914-like simulated events -- detected by the current infrastructure of ground-based detectors at their design sensitivity -- it is possible to confidently falsify the quantised model or prove its validity, in which case probing α at the few % level. Finally we classify the stealth biases that may show up in a population study
Testing general relativity with compact coalescing binaries: Comparing exact and predictive methods to compute the Bayes factor
No full textThe second generation of gravitational-wave detectors is scheduled to start operations in 2015. Gravitational-wave signatures of compact binary coalescences could be used to accurately test the strong-field dynamical predictions of general relativity (GR). Computationally expensive data analysis pipelines, including TIGER (test infrastructure for general relativity), have been developed to carry out such tests. As a means to cheaply assess whether a particular deviation from GR can be detected, Cornish et al (2011 Phys. Rev. D 84 062003) and Vallisneri (2012 Phys. Rev. D 86 082001) recently proposed an approximate scheme to compute the Bayes factor between a GR gravitational-wave model and a model representing a class of alternative theories of gravity parametrized by one additional parameter. This approximate scheme is based on only two easy-to-compute quantities: the signal-to-noise ratio (SNR) of the signal and the fitting factor (FF) between the signal and the manifold of possible waveforms within GR. In this work, we compare the prediction from the approximate formula against an exact numerical calculation of the Bayes factor using the lalinference library. We find that, using frequency-domain waveforms, the approximate scheme predicts exact results with good accuracy, providing the correct scaling with the SNR at a FF value of 0.992 and the correct scaling with the FF at a SNR of 20, down to a FF of ∼0.9. We extend the framework for the approximate calculation of the Bayes factor, which significantly increases its range of validity, at least to FFs of ∼0.7 or higher
Searching for ringdown higher modes with a numerical relativity-informed post-merger model
No full textRobust measurements of multiple black hole vibrational modes provide a unique opportunity to characterise gravity in extreme curvature and dynamical regimes, to better investigate the nature of compact objects and search for signs of new physics. We use a numerically-tuned quasicircular non-precessing ringdown model, TEOBPM, and the pyRing analysis infrastructure to perform a time-domain spectroscopic analysis of the third catalog of transient gravitational-wave signals, GWTC-3, searching for higher angular modes. The TEOBPM model effectively includes non-linearities in the early post-merger signal portion, and carries information about the progenitors parameters through time-dependent excitation amplitudes of the black hole quasinormal modes. Such a strategy allows us to accurately model the full post-merger emission, recovering higher signal-to-noise ratios compared to templates based on more agnostic superpositions of damped-sinusoids. We find weak evidence for the presence of [] mode in several events, with the largest Bayes factor in favour of this mode being [] within the support of the peak time distribution. For GW190521, we observe , but only for times outside the peak time support reconstructed using the highly accurate NRSur7dq4 model, indicating significant systematics affecting such putative detection. Allowing for deviations from general relativity under the assumption of the presence of two modes, we find tentative support for the Kerr “final state conjecture”. Our work showcases a systematic methodology to robustly identify and characterise higher angular modes in ringdown-only signals, highlighting the significant impact of modelling assumptions and peak time uncertainty on spectroscopic measurements, at current signal-to-noise ratios
Cosmological inference using only gravitational wave observations of binary neutron stars
Full text linkGravitational waves emitted during the coalescence of binary neutron star systems are self- calibrating signals. As such, they can provide a direct measurement of the luminosity distance to a source without the need for a cross-calibrated cosmic distance-scale ladder. In general, how- ever, the corresponding redshift measurement needs to be obtained via electromagnetic observations since it is totally degenerate with the total mass of the system. Nevertheless, Fisher matrix studies have shown that, if information about the equation of state of the neutron stars is available, it is possible to extract redshift information from the gravitational wave signal alone. Therefore, measuring the cosmological parameters in pure gravitational-wave fashion is possible. Furthermore, the huge number of sources potentially observable by the Einstein Telescope has led to speculations that the gravitational wave measurement is potentially competitive with traditional methods. The Einstein Telescope is a conceptual study for a third generation gravitational wave detector which is designed to yield 103 − 107 detections of binary neutron star systems per year. This study presents the first Bayesian investigation of the accuracy with which the cosmological parameters can be measured using information coming only from the gravitational wave observations of binary neutron star systems by Einstein Telescope. We find, by direct simulation of 103 detections of binary neutron stars, that, within our simplifying assumptions, H0, Ωm, ΩΛ, w0 and w1 can be measured at the 95% level with an accuracy of ∼ 8%,65%,39%,80% and 90%, respectively. We also find, by extrapolation, that a measurement accuracy comparable with current measurements by Planck is possible if the number of gravitational wave events observed is O(10^{6−7}).We conclude that, while not competitive with electro-magnetic missions in terms of significant digits, gravitational wave alone are capable of providing a complementary determination of the dynamics of the Universe
On tests of general relativity with binary radio pulsars
Full text linkThe timing of radio pulsars in binary systems provides a superb testing ground of general relativity. Here we propose a Bayesian approach to carry out these tests, and a relevant efficient numerical implementation, that has several conceptual and practical advantages with respect to traditional methods based on least-squares fit that have been used so far: (i) it accounts for the actual structure of the likelihood function - and it is not predicated on the Laplace approximation which is implicitly built in least-squares fit that can potentially bias the inference - (ii) it provides the ratio of the evidences of any two models under consideration as the statistical quantity to compare different theories, and (iii) it allows us to put joint constraints from the monitoring of multiple systems, that can be expressed in terms of ratio of evidences or probability intervals of global (thus not system-dependent) parameters of the theory, if any exists. Our proposed approach optimally exploits the progress in timing of radio pulsars and the increase in the number of observed systems.We demonstrate the power of this framework using simulated data sets that are representative of current observations
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