Abstract
We obtain the solution of a static spherically symmetric black hole surrounded by a cloud of strings in Rastall gravity and study the influence of the parameter $a$ associated with strings on the event horizon and the Hawking temperature. Through analyzing the black hole metric, we find that the static spherically symmetric black hole solution surrounded by a cloud of strings in Rastall gravity can be transformed into the static spherically symmetric black hole solution surrounded by quintessence in Einstein gravity when the parameter $\beta$ of Rastall gravity is positive, which provides a possibility for the string fluid to be a candidate of dark energy. We use the method of Regge and Wheeler together with the high order WKB-Pad\'{e} approximation to calculate the quasinormal mode frequencies of the odd parity gravitational perturbation and simultaneously apply the unstable null geodesics of black holes to compute the quasinormal mode frequencies at the eikonal limit for this black hole model. The results show that the increase of the parameter $a$ makes the gravitational wave decay slowly in Rastall gravity. In addition, we utilize two methods, which are based on the adiabatic invariant integral and the periodic property of outgoing waves, respectively, to derive the area spectrum and entropy spectrum of the black hole model. The results show that the area spectrum and entropy spectrum are equidistant spaced. The former is same as the case of Einstein gravity, while the latter is different, depending on the Rastall parameter $\beta$.
Highlights
The gravitational waves from binary black hole or neutron star mergers detected by LIGO and Virgo collaborations [1,2], as well as the first black hole photograph released recently, have fueled our interest in black holes
II, we first find out the exact solution of a static spherically symmetric black hole surrounded by a cloud of strings in Rastall gravity
In order to derive the solution of a Schwarzschild black hole surrounded by a cloud of strings in Rastall theory, we consider the following static spherically symmetric metric: ds2 1⁄4 fðrÞdt2 − f−1ðrÞdr2 − r2ðdθ2 þ sin2 θdφ2Þ; ð5Þ
Summary
The gravitational waves from binary black hole or neutron star mergers detected by LIGO and Virgo collaborations [1,2], as well as the first black hole photograph released recently, have fueled our interest in black holes. Our aim is to analyze the quasinormal modes of a Schwarzschild black hole surrounded by a cloud of strings in Rastall gravity. We adopt the method of the adiabatic invariant integral [17] and that of the periodic property of outgoing waves [25] to derive the area spectrum and entropy spectrum of the black hole model, respectively, so as to give the influence of Rastall gravity and of strings on the area spectrum and entropy spectrum. Throughout this paper, we adopt the units c 1⁄4 G 1⁄4 kB 1⁄4 1 and the sign convention ðþ; −; −; −Þ
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