Bulletin of the American Physical Society
APS April Meeting 2023
Volume 68, Number 6
Minneapolis, Minnesota (Apr 15-18)
Virtual (Apr 24-26); Time Zone: Central Time
Session U08: Quasi-Normal Modes and Memory |
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Sponsoring Units: DGRAV Chair: Maximiliano Isi, Massachusetts Institute of Technology MIT Room: Symphony III - 2nd Floor |
Tuesday, April 18, 2023 1:30PM - 1:42PM |
U08.00001: Towards a more robust algorithm for computing the Kerr quasinormal mode frequencies Sashwat Tanay, Leo C Stein Leaver's method has been the standard for computing the quasinormal mode (QNM) frequencies for a Kerr black hole (BH) for a few decades. We start with a spectral variant of Leaver's method introduced by Cook and Zalutskiy [Phys. Rev. D 90, 124021 (2014)], and propose improvements in the form of computing the necessary derivatives analytically, rather than by numerical finite differencing. We also incorporate this derivative information into qnm, a Python package, which finds the QNM frequencies via the spectral variant of Leaver's method. We confine ourselves to first derivatives only |
Tuesday, April 18, 2023 1:42PM - 1:54PM |
U08.00002: A Surrogate Model for Ringdown Lorena MagaƱa Zertuche, Leo C Stein Next generation ground- and space-based detectors will provide us with hundreds of gravitational wave signals from binary black holes, and we will rely on quick, high-fidelity models to extract as much information as possible from these signals. LISA will have high enough sensitivity to capture multiple ringdown frequencies, enabling tests of general relativity. I will present current progress towards our multimode ringdown surrogate, which uses waveforms that are in the Bondi-van der Burg-Metzner-Sachs super rest frame. We use Gaussian process regression, a sophisticated mathematical tool to find joint Gaussian distributions between parameters and data. In future work this high-precision ringdown surrogate model may be incorporated into a full waveform surrogate. |
Tuesday, April 18, 2023 1:54PM - 2:06PM |
U08.00003: Black hole spectroscopy by mode cleaning Sizheng Ma, Ling Sun, Yanbei Chen At the final stage of the collision of two black holes, the newly formed remnant black hole rings at specific characteristic frequencies and decay rates. The ringdown gravitational waves are described by the superposition of these complex-valued, quasinormal modes (QNMs), which are determined solely by the remnant black hole's mass and spin according to the no-hair theorem. We propose a novel framework for ringdown analysis using a set of frequency-domain rational filters designed to remove any given QNMs. By cleaning the dominant fundamental mode in the data of a gravitational-wave event, we are able to probe weaker modes and subdominant effects. This new method provides a rigorous and powerful tool to analyze experimental data and interrogate the nature of gravity. In this talk, I will first introduce the filters and describe the Bayesian framework based on mode cleaning. Next, I will demonstrate the application of the method and uncover the first overtone in the ringdown of GW150914. |
Tuesday, April 18, 2023 2:06PM - 2:18PM |
U08.00004: Post-merger chirp morphology and parameterization Chad Henshaw, Laura Cadonati The gravitational waves produced by binary black hole systems with an asymmetric mass ratio have been shown to exhibit a characteristic double-chirp pattern when viewed from a highly inclined orientation. These chirp patterns are composed of mixed higher-order modes produced during the ringdown, due to regions of high curvature on the distorted apparent horizon. Herein we motivate a means to reduce the double-chirp phenomenon into a single-number parameter that describes its strength relative to that of the overall signal. This is accomplished by adapting a continuous wavelet transform scan to utilize a chirplet (a Sine-Guassian wavelet with a forward chirp rate) as the mother wavelet, enhancing the contrast of the spectrogram. The development of this technique is discussed, along with prospects towards mapping the apparent horizon evolution. |
Tuesday, April 18, 2023 2:18PM - 2:30PM |
U08.00005: Quasi-normal Modes of Topological Stars Nicholas Speeney, Emanuele Berti, Pierre Heidmann We study the quasi-normal mode spectrum of topological stars which have the same asymptotic properties as black holes. These are coherent states in string theory corresponding to pure deformations of spacetime through the dynamics of compact extra dimensions. The topological stars are classified as either "first" or "second" kind, based on the presence of either one or two light rings, respectively. The quasi-normal mode spectrum is analytically computed using a WKB analysis, and compared with a numerically generated spectrum using Leaver's method. We discuss the connection between the quasi-normal modes and the physics of the unstable light-rings, in both cases of the "first" and "second" kind of topological star. We find good agreement with numerical and analytic results, comparable to the WKB level agreement in Schwarzschild black holes. |
Tuesday, April 18, 2023 2:30PM - 2:42PM |
U08.00006: Investigating the Fidelity of the QNM Amplitudes in Ringdown Fitting Leda Gao, Gregory B Cook Considering aspects of multimodes ringdown fitting, increasing the number of QNMs and overtones is a frequent approach to improve the quality of multimode ringdown fitting. However, the fidelity of the QNM amplitudes obtained from fitting is not fully understood. In other words, some QNMs in the model are not fit robustly even though the fitting quality of some other quantities, like the mismatch and remnant parameters, has improved. To explore the robustness of QNM fitting, a method resembling the greedy algorithm is applied to a multimode QNM-fitting approach. The QNM coefficients in this technique tend to be fixed iteratively as the program runs. |
Tuesday, April 18, 2023 2:42PM - 2:54PM |
U08.00007: Fitting Multiple Quasinormal Modes to the Ringdown of GW190521 Harrison Siegel, Maximiliano Isi, Will M Farr We report on the fitting of damped sinusoids to the ringdown of GW190521. We find that our analysis prefers fits which at least include both the 220 and 210 quasinormal modes, as opposed to other combinations of modes that have been presented previously in the literature. Our analysis notably suggests that the amplitudes of the 220 and 210 could be comparable: previous theoretical studies of ringdown quasinormal mode excitation do not predict such a large amplitude ratio, however most of the literature so far has focused on spin-aligned binary black-hole progenitors whose behavior may be substantially different from systems such as GW190521 which have evidence of significant spin misalignment. Additionally, we briefly discuss our efforts to analyze the ringdowns in the rest of the LIGO catalogue. The possibility of measuring the 210 and other fundamental modes in GW190521 and in other events has broad implications for our understanding of fundamental aspects of black-hole physics, and should enhance the power of tests of general relativity. |
Tuesday, April 18, 2023 2:54PM - 3:06PM |
U08.00008: Outlook for detecting gravitational wave memory effects with current and future gravitational wave detectors Alexander M Grant, David A Nichols Gravitational wave memory effects appear as non-oscillatory components in a gravitational wave signal, and they are predictions of general relativity in the nonlinear regime that have close connections to the asymptotic properties of isolated gravitating systems. Of these effects, the "displacement" and "spin" memories are expected to be the largest that will be generated from sources such as the binary black hole mergers which have already been detected by LIGO and Virgo. 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. While LIGO, Virgo, and KAGRA can only detect memory effects from individual events that are much louder (and thus rarer) than those that have been detected so far, by combining data from multiple events, these effects could be detected in a population of binary mergers. In this talk, we present new forecasts for how long current detectors (LIGO, Virgo, and KAGRA) and future detectors (Cosmic Explorer) 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. |
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