Greybody factor and quasinormal modes of Regular Black Holes
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Regular Article - Theoretical Physics
Greybody factor and quasinormal modes of Regular Black Holes Ángel Rincón1,a , Victor Santos2,b 1 2
Instituto de Física, Pontificia Universidad Católica de Valparaíso, Avenida Brasil 2950, Casilla, 4059 Valparaíso, Chile Fundação Cearense de Apoio ao Desenvolvimento Científico e Tecnológico (FUNCAP), Av. Oliveira Paiva, 941, Cidade dos Funcionários, Fortaleza, CE 60822-130, Brazil
Received: 20 July 2020 / Accepted: 5 September 2020 © The Author(s) 2020
Abstract In this work, we investigate the quasinormal frequencies of a class of regular black hole solutions which generalize Bardeen and Hayward spacetimes. In particular, we analyze scalar, vector and gravitational perturbations of the black hole with the semianalytic WKB method. We analyze in detail the behaviour of the spectrum depending on the parameter p/q of the black hole, the quantum number of angular momentum and the s number. In addition, we compare our results with the classical solution valid for p = q = 1.
1 Introduction One of the most striking predictions of General Relativity (GR) [1] is the existence of Black Holes (BHs), objects which produce a region where not even light can escape. They can be formed in the extreme final stages of the gravitational collapse of stars. Such astrophysical objects are remarkably simple, being characterized by three parameters: mass, charge and angular momentum, by virtue of the so-called “no-hair” theorems [2–4]. Since gravitational radiation emitted by an oscillating black hole can carry information about its inner properties like mass and charge [5,6], this enables to use BHs as a laboratory for studying gravity in strong regimes, where quantum phenomena might take uttermost importance. Also, after Hawking’s seminal papers where the radiation from the black hole horizon was explained [5,6], black boles become an excellent laboratory to study and also enhance our comprehension about quantum gravity. Naively, the Hawking radiation is taken as black body radiation parametrized by the hawking temperature TH . However, the latter is just an approximated picture because emitted particles feel an effective potential barrier in the exterior region. Such barrier backscatters a percentage of the outgoing radiation back into a e-mail:
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the black hole [7]. Thus, the spectrum of the Hawking radiation as seen by an asymptotic observer has not a complete blackbody distribution: it is better described by a greybody distribution. The greybody factor can obtained from the transmission amplitude as the field modes pass from near horizon region to an asymptotic observer through the effective potential induced by the spacetime geometry. Estimation of this greybody factor is usually a difficult task and often one has to resort to approximations, usually in low/high frequency limits. There are monodromy methods [8,9] and computations in a variety of scenarios [10–13], where one can also em
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