Naked singularity in 4D Einstein-Gauss-Bonnet novel gravity: Echoes and (in)-stability

Abstract

We study the stability of an asymptotically flat, static, spherically symmetric naked singularity spacetime in the novel four dimensional Einstein-Gauss-Bonnet (EGB) gravity. The four dimensional EGB black hole for large enough values of the coupling parameter leads to such a naked singularity. The stability and the response of the spacetime is studied against the perturbations by test scalar, electromagnetic and Dirac fields and the time evolution of these perturbations were observed numerically. Implementing a null Dirichlet boundary condition near the singularity, we observed that for l = 1 modes of scalar, electromagnetic perturbation and l = 0, 1 modes of Dirac perturbation the time-domain profile give rise to distinct echoes. However, as the coupling constant is increased, the echoes align and the QNM structure of the 4D-EGB naked singularity-spacetime becomes prominent. For higher values of the multipole number, the spacetime becomes unstable, thereby restricting the parameter space for the coupling parameter.

Quasinormal modes of black holes in f(T) gravity

“…Hence, one can use gravitational-wave observations in order to test general relativity, examining for instance the validity of the "no-hair theorem" [74][75][76], and use the predictions of QNM properties to constrain and classify modified gravity theories [77][78][79][80][81][82][83][84][85]. Furthermore, the QNM frequency can also partly reveal the stability of spacetime geometry under small perturbations [86,87]. Hence, the study of QNM has become a concerned topic [88][89][90][91].…”

Spherical Gravitational Collapse in 4D Einstein- Gauss- Bonnet theory

“…How does one quantify them, and what role shall they play in quantum theory? Third, one also should determine the stability and experimental signatures of such spacetime structures [42]. These studies shall be carried out in the future.…”