Bulletin of the American Physical Society
APS April Meeting 2020
Volume 65, Number 2
Saturday–Tuesday, April 18–21, 2020; Washington D.C.
Session J15: Tests of General Relativity with Gravitational Waves ILive
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Sponsoring Units: DGRAV Chair: Miriam Cabero, The University of British Columbia Room: Virginia B |
Sunday, April 19, 2020 1:30PM - 1:42PM Live |
J15.00001: Post-Newtonian Dynamics of Black Hole Binaries in Einstein-Scalar-Gauss-Bonnet Gravity Felix-Louis Julie, Emanuele Berti We study the post-Newtonian dynamics of binary black holes in Einstein-scalar-Gauss-Bonnet gravity theories. To this aim we build static, spherically symmetric black hole solutions at high order in the Gauss-Bonnet coupling. We then reduce these solutions to point particles with scalar field-dependent masses, showing that this procedure amounts to fixing the Wald entropy of the black holes during their slow inspiral. We compute the two-body Lagrangian at first post-Newtonian order and show that no regularization procedure is needed to obtain the Gauss-Bonnet contributions to the fields, which are finite. Finally, we illustrate the power of our approach by Pad\'e-resumming the so-called “sensitivities,” which measure the bodies’ couplings to the scalar field, for some specific theories of interest. [Presentation based on Phys.Rev. D100 (2019) no.10, 104061] [Preview Abstract] |
Sunday, April 19, 2020 1:42PM - 1:54PM Live |
J15.00002: Suppression of nonperturbative strong field effects in gravity theories Fethi M Ramazanoglu A modification to general relativity (GR) is particularly interesting when it deviates from GR slightly in weak gravitational fields and by a large amount in the strong-field regime. The former ensures that known observational bounds are satisfied, and the letter makes the theory relevant for gravitational wave detections, our primary source of information for strong-field gravity, which have limited precision. Spontaneous scalarization scenario in scalar-tensor theories is a well-known example of such a theory, where an additional scalar degree of freedom is the culprit for the deviations from GR. Recent work has shown that other fields such as vectors lead to similar results. We will present our investigation of the natural generalization of these two theories where scalars and vectors are both spontaneously growing. The idea might seem straightforward at first, but the effects of scalars and vectors on gravity are “opposite” in a mathematically precise sense, hence, their combination can lead to the suppression of deviations from GR. This can have important consequences for the detectability of the modifications of GR using gravitational waves. [Preview Abstract] |
Sunday, April 19, 2020 1:54PM - 2:06PM Live |
J15.00003: Probing scalar-tensor theories with gravitational waves from neutron star-black hole binaries Kent Yagi, Zack Carson, Brian Seymour The extreme-gravity collisions of binaries with one black hole and one neutron star provide for excellent tests of general relativity. In this talk, we explain how well one can constrain theories beyond general relativity with additional scalar fields that allow for spontaneous scalarization of neutron stars and those motivated from string theory. We find that existing bounds can be improved with current gravitational-wave detectors if the black hole mass is sufficiently small. Bounds will further improve by many orders of magnitude with future detections, especially by combining multiple events. [Preview Abstract] |
Sunday, April 19, 2020 2:06PM - 2:18PM |
J15.00004: Fundamental Physics Implications on Higher-Curvature Theories from the Binary Black Hole Signals in the LIGO-Virgo Catalog GWTC-1 Scott Perkins, Remya Nair, Hector Silva, Nicolas Yunes Gravitational-wave astronomy offers not only new vistas into the realm of astrophysics, but 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. In this talk, I will present a study of whether the gravitational-wave events detected so far by the LIGO-Virgo scientific collaborations can be used to probe high-curvature corrections to general relativity. I will focus on two example theories: Einstein-dilaton-Gauss-Bonnet and dynamical Chern-Simons gravity. To illustrate our methodology, I will first outline how our bounds can be estimated from analytic calculations, then through another estimate using the Fisher matrix, and finally through the full posteriors released by LIGO/Virgo, which were obtained through Markov Chain Monte Carlo sampling. To finish, I will discuss the final constraints produced by the two events GW151226 and GW170608 on Einstein-dilaton-Gauss-Bonnet and dynamical Chern-Simons gravity. [Preview Abstract] |
Sunday, April 19, 2020 2:18PM - 2:30PM |
J15.00005: Gravitational waves from the quasi-circular inspiral of compact binaries in Einstein-aether theory Chao Zhang, Xiang Zhao, Anzhong Wang, Bin Wang, Kent Yagi, Nicolas Yunes, Wen Zhao, Tao Zhu We study gravitational waves (GWs) emitted by a binary system of non-spinning bodies in a quasi-circular inspiral within the Einstein-aether theory. In particular, we compute explicitly and analytically the expressions for the time-domain and frequency-domain waveforms, GW polarizations, and response functions for both ground- and space-based detectors in the post-Newtonian (PN) approximation. We find that, when going beyond leading-order in the PN approximation, the non-Einsteinian polarization modes contain terms that depend on both the first and the second harmonics of the orbital phase. We also calculate analytically the corresponding parameterized post-Einsteinian parameters, generalizing the existing framework to allow for different propagation speeds among scalar, vector and tensor modes. Such results allow for the easy construction of Einstein-aether templates that could be used in Bayesian tests of general relativity in the future. [Preview Abstract] |
Sunday, April 19, 2020 2:30PM - 2:42PM On Demand |
J15.00006: Theory-agnostic framework for dynamical scalarization of compact binaries Mohammed Khalil, Noah Sennett, Jan Steinhoff, Alessandra Buonanno Several classes of modified theories of gravity suggest that gravity may undergo a phase transition ---known as spontaneous scalarization--- in the strong-field regime. The detection of such a new phase would constitute a smoking-gun for corrections to general relativity at the classical level. Using a strong-field-agnostic effective-field-theory approach, we show that all theories that exhibit spontaneous scalarization can also manifest dynamical scalarization, a phase transition associated with symmetry breaking in a binary system. We derive an effective point-particle action that provides a simple parametrization describing both phenomena, which establishes a foundation for theory-agnostic searches for scalarization in gravitational-wave observations. This parametrization can be mapped onto any theory in which scalarization occurs; we demonstrate this point explicitly for binary black holes with modified electrodynamics. [Preview Abstract] |
Sunday, April 19, 2020 2:42PM - 2:54PM Not Participating |
J15.00007: Black hole mergers in quadratic gravity Helvi Witek Observations and deeply theoretical considerationsindicatethat general relativity, our elegant standard model of gravity, requires modifications at high curvatures scales. Candidate theories of quantum gravity, in their low-energy limit, typically predict couplings to additional fields or involve higher curvature terms. At the same time, the breakthrough discovery of gravitational waves has provided a new channel to probe gravity in its most extreme, truly nonlinear regime. Modelling the expected gravitational radiation in extensions of GR enables us to search for -- or place novel observational bounds on -- deviations from our standard model. In this talk I will give an update onthe progress on simulating black-holebinary mergersin quadratic gravity and the understanding of new mathematical challenges such as the well-posedness of the underlying initial value formulation. [Preview Abstract] |
Sunday, April 19, 2020 2:54PM - 3:06PM Not Participating |
J15.00008: Numerical relativity simulations of GW150914 beyond General Relativity Maria Okounkova We present the first astrophysically-relevant numerical binary black hole gravitational waveforms in higher-curvature theories of gravity beyond general relativity. We simulate a system with parameters consistent with GW150914, the first LIGO detection, in order-reduced dynamical Chern-Simons gravity, a theory with motivations in string theory and loop quantum gravity, and order-reduced Einstein dilaton Gauss-Bonnet gravity, a theory with motivations in string theory. We present results for the leading-order corrections to the merger and ringdown waveforms, and place estimates on detecting and constraining these beyond-GR effects with LIGO. [Preview Abstract] |
Sunday, April 19, 2020 3:06PM - 3:18PM Not Participating |
J15.00009: Polarization modes of gravitational waves in quadratic gravity Pratik Wagle, Alexander Saffer, Nicolas Yunes The observation of the inspiral and merger of compact binaries by the LIGO-Virgo collaboration has allowed for new tests of Einstein's theory in the extreme gravity regime, where gravitational interactions are simultaneously strong, non-linear, and dynamical. Theories beyond Einstein's can also be constrained by detecting the polarization modes of gravitational waves. In this talk, I will show that dynamical Chern-Simons gravity and Einstein-dilaton-Gauss-Bonnet gravity cannot be differentiated from general relativity based on the detection of polarization modes alone. To prove this result, I will be using the Newman-Penrose method and an irreducible decomposition method to find that only the tensorial (plus- and cross-polarization) modes can be detected in both these theories. [Preview Abstract] |
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