Bulletin of the American Physical Society
APS April Meeting 2022
Volume 67, Number 6
Saturday–Tuesday, April 9–12, 2022; New York
Session S15: Gravitational Memory and RingdownRecordings Available
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Sponsoring Units: DGRAV Chair: Shahar Hadar Room: Marquis C |
Monday, April 11, 2022 1:30PM - 1:42PM |
S15.00001: Infrared Finite Scattering Theory in QFT and Quantum Gravity Gautam Satishchandran, Robert M Wald, Kartik Prabhu The "infrared problem" is the generic emission of an infinite number of low-frequency quanta in any scattering process with massless degrees of freedom. That the ``out'' state contains an infinite number of such quanta implies that it does not lie in the standard Fock representation. Consequently, the standard S-matrix is undefined as a map between "in" and "out" states in the standard Fock space. This fact is due to the existence of a low-frequency tail of the radiation field (i.e. the memory effect) as well as the existence of an infinite number of conserved charges at spatial infinity. In massive QED, the scattering representations known as "Kulish-Faddeev" representations have been argued to yield an I.R. finite S-matrix. We clarify the "preferred status" of such representations as eigenstates of the conserved ``large gauge charge''. We prove a "No-Go" theorem for the existence of a suitable Hilbert space analogously constructed scattering states in massless QED, QCD, linearized quantum gravity with massive/massless sources, and in full quantum gravity. We then develop an "infrared-finite" formulation of scattering theory without any a priori choice of "in/out" Hilbert space. |
Monday, April 11, 2022 1:42PM - 1:54PM |
S15.00002: Angular momentum, BMS charges, twistors and scattering Adam D Helfer The BMS charges form a well-defined set of asymptotic kinematic quantities of significant interest; there has been considerable work interpreting the charges as conserved quantities conjugate to BMS motions. However, the charges were originally proposed as part of a treatment of angular momentum, and this interpretation is more problematic. While there is a formal parallel between the BMS and Poincare structures, attempts to interpret the BMS charges as spin and center of mass run into difficulties. I will explain the infinite-dimensional ambiguity in the charge-based center of mass, and the related failure of supertranslation invariance for the charge-based spin [1]. |
Monday, April 11, 2022 1:54PM - 2:06PM |
S15.00003: Forecasting the detection of gravitational wave memory by current and future gravitational wave detectors Alexander M Grant, David A Nichols Gravitational wave memory effects are non-oscillatory components of gravitational wave signals that provide interesting tests of general relativity in the nonlinear regime. There are many types of memory effects that have been studied in the literature; in this talk we focus on the "displacement" and "spin" memories, which are expected to be the largest effects from binary black hole mergers. The displacement memory is a change in the relative separation of two initially comoving observers due to a burst of gravitational waves, whereas the spin memory is a portion of the change in relative separation of observers with initial relative velocity. As both of these effects are small, detection by LIGO, Virgo, and KAGRA is unlikely for single events. However, by combining data from multiple events, these effects could potentially be detected in a population of binary mergers. In this talk, we present estimates for how long current and future detectors will need to operate in order to measure these effects from populations of binary black hole systems that are consistent with the populations inferred from the detections from LIGO and Virgo's first three observing runs. |
Monday, April 11, 2022 2:06PM - 2:18PM |
S15.00004: Waveform models for the gravitational-wave memory effect Arwa Z Elhashash, David A Nichols The gravitational-wave (GW) memory effect causes a lasting relative displacement of freely falling observers before and after the passage of a transient source of GWs. The effect was first computed in the 1970s, but only with upcoming improvements to the LIGO, Virgo, and KAGRA detectors will the prospects of detecting the effect in a population of binary-black-hole (BBH) mergers be promising. Methods to detect the memory effect require accurate waveform models that can be evaluated rapidly, because these methods to assess the significance of the memory require many waveform evaluations. Current analytical waveform models, and many numerical-relativity (NR) simulations and surrogates, do not include the waveform related to the GW memory effect; instead, the waveform is computed as a secondary step from waveform models without the memory by employing conservation laws in asymptotically flat spacetimes. We instead develop stand-alone time- and frequency-domain waveform models of the GW memory effect for nonspinning BBH mergers. We incorporate data from both NR surrogate models and the extreme mass-ratio limit to develop a waveform model that can be applied to all mass ratios. |
Monday, April 11, 2022 2:18PM - 2:30PM |
S15.00005: The Importance of BMS Frames for Gravitational Wave Modeling Keefe Mitman, Leo C Stein, Neev Khera, Lorena Magaña Zertuche As was realized by Bondi, Metzner, van der Burg, and Sachs (BMS), the symmetry group of asymptotic infinity is not the Poincaré group, but an infinite dimensional group called the BMS group. Because of this, understanding the BMS frame of the gravitational waves produced by numerical relativity is crucial for ensuring that analyses and comparisons with other waveform models are performed properly. Up until now, however, the BMS frame of numerical waveforms has not been thoroughly examined, largely because the necessary tools have not existed. In this talk, I will highlight an improved method for fixing the BMS frame of numerical waveforms. Following this, I will then illustrate how this new scheme of fixing the BMS frame allows for much faster and more correct comparisons between numerical relativity waveforms and either Post-Newtonian or Quasi-normal Mode models, which will prove vitally important for testing Einstein's theory of relativity with observations obtained by gravitational wave observatories. |
Monday, April 11, 2022 2:30PM - 2:42PM |
S15.00006: High Precision Multimode Ringdown Fitting Lorena Magaña Zertuche, Keefe Mitman, Neev Khera, Leo C Stein Binary black hole ringdown studies are crucial in understanding astrophysical black holes and provide a consistency check between perturbation theory and numerical relativity. Third generation gravitational-wave detectors will be much more sensitive to multiple ringdown frequencies, thereby requiring high precision ringdown models. In this talk, I will introduce a new multimode ringdown fitting model which incorporates spherical-spheroidal mixing, retrograde modes, and overtones. In addition, the numerical relativity waveforms used to fit for the mode amplitudes are mapped to the Bondi-van der Burg-Metzner-Sachs super rest frame, the canonical frame to use in ringdown analyses resulting from the Teukolsky formalism. Working in this correct frame allows us to get up to a 105 order of magnitude improvement in the mismatches between numerical relativity simulations and our analytical ringdown model. |
Monday, April 11, 2022 2:42PM - 2:54PM |
S15.00007: Gravitational wave tomography: the ringdown regime Neev Khera, Abhay V Ashtekar As a black hole remnant settles down to its final state, its dynamical horizon asymptotically approaches equilibrium. However, the horizon dynamics cannot be directly observed from null infinity because it is causally disconnected. Nonetheless, using Einstein's equations and the linearized approximation in the ringdown regime, we show that we can infer the strong field dynamics of the black hole horizon from the weak field gravitational waves. In particular, this can be used to test the starting time of ringdown regime and in numerical simulations and identify overfitting of the ringdown waveform. |
Monday, April 11, 2022 2:54PM - 3:06PM |
S15.00008: Angular emission patterns of remnant black holes Xiang Li, Ling Sun, Rico Ka Lok Lo, Ethan Payne, Yanbei Chen The gravitational radiation from the ringdown of a binary black hole merger is described by the solution of the Teukolsky equation, which predicts both the temporal and angular dependence of the emission. Many studies have explored the temporal feature of the ringdown wave through black hole spectroscopy. In this work, we further study the spatial distribution, by introducing a global fitting procedure over both temporal and spatial dependences, to propose a more complete test of General Relativity. We show that spin-weighted spheroidal harmonics are the better representation of the ringdown angular emission patterns compared to spin-weighted spherical harmonics. The differences are distinguishable in numerical relativity waveforms. We also study the correlation between progenitor binary properties and the excitation of quasinormal modes, including higher-order angular modes, overtones, prograde and retrograde modes. Specifically, we show that the excitation of retrograde modes is dominant when the remnant spin is anti-aligned with the binary orbital angular momentum. This study seeks to provide an analytical strategy and inspire the future development of ringdown test using real gravitational wave events. |
Monday, April 11, 2022 3:06PM - 3:18PM |
S15.00009: Multimode Kerr Ringdown Fitting for Precessing BBH Mergers Leda Gao, Gregory B Cook Multimode fitting of the ringdown signal for a precessing BBH merger system is investigated. We explore numerically generated waveforms from the Simulating eXtreme Spacetimes(SXS) catalog. Fitting cases with different combinations of simulation modes and QNM modes are explored. The overall quality of the fits and the fidelity of the QNM expansion coefficients extracted from the fitting is investigated from two perspectives, that of the relative and the absolute amplitudes. |
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