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Analytical computation of quasinormal modes of slowly rotating black holes in dynamical Chern-Simons gravity

Srivastava, Manu and Chen, Yanbei and Shankaranarayanan, S. (2021) Analytical computation of quasinormal modes of slowly rotating black holes in dynamical Chern-Simons gravity. Physical Review D, 104 (6). Art. No. 064034. ISSN 2470-0010. doi:10.1103/physrevd.104.064034.

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Using gravitational wave observations to search for deviations from general relativity (GR) in the strong-gravity regime has become an important research direction. One aspect of the strong gravity modifications to GR is parity violation. Chern Simons (CS) gravity is one of the most frequently studied parity-violating models of strong gravity. CS gravity is indistinguishable from GR for all conformally flat space-times and for space-times that possess a maximally symmetric two-dimensional subspace. Also, it is known that the Kerr black hole is not a solution for CS gravity. At the same time, the only rotating solution available in the literature for dynamical CS (DCS) gravity is the slow-rotating case most accurately known to quadratic order in spin. In this work, for the slow-rotating case (accurate to first order in spin), we derive the linear perturbation equations governing the metric and the DCS field accurate to linear order in spin and quadratic order in the CS coupling parameter (α) and obtain the quasinormal mode (QNM) frequencies. After confirming the recent results of Wagle et al. arXiv:2103.09913, we find an additional contribution to the eigenfrequency correction at the leading perturbative order of α². Unlike Wagle et al., we also find corrections to frequencies in the polar sector. We compute these extra corrections by evaluating the expectation values of the perturbative potential on unperturbed QNM wave functions along a contour deformed into the complex-r plane. For α = 0.1 M², we obtain the ratio of the imaginary parts of the DCS correction to the GR correction in the first QNM frequency (in the polar sector) to be 0.263 implying significant change. For the (2, 2) mode, the DCS corrections make imaginary part of the first QNM of the fundamental mode less negative, thereby decreasing the decay rate. Our results, along with future gravitational wave observations, can be used as a test for DCS gravity and to further constrain the CS coupling parameters.

Item Type:Article
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URLURL TypeDescription Paper
Srivastava, Manu0000-0002-3831-6997
Chen, Yanbei0000-0002-9730-9463
Shankaranarayanan, S.0000-0002-7666-4116
Alternate Title:Analytical computation of quasi-normal modes of slowly-rotating black-holes in dCS gravity
Additional Information:© 2021 American Physical Society. (Received 18 June 2021; accepted 6 August 2021; published 13 September 2021) The authors thank Vitor Cardoso, Leonardo Gualtieri, Dongjun Li, Archana Pai, and Nicolas Yunes for helpful discussions. This work is part of the Dual Degree thesis project of M. S.. The work of S. S. is supported by SERB-MATRICS grant. Y. C. is supported by the Simons Foundation (Grant No. 568762), the Brinson Foundation, and the National Science Foundation (Grants No. PHY–2011968, No. PHY–2011961, and No. PHY–1836809).
Funding AgencyGrant Number
Science and Engineering Research Board (SERB)UNSPECIFIED
Simons Foundation568762
Brinson FoundationUNSPECIFIED
Issue or Number:6
Record Number:CaltechAUTHORS:20210927-213255784
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:111058
Deposited By: George Porter
Deposited On:27 Sep 2021 22:55
Last Modified:27 Sep 2021 22:55

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