Schwarzschild-like black holes: Light-like trajectories and massless scalar absorption

Abstract

Black holes are among the most intriguing objects in nature. They are believed to be fully described by General Relativity (GR), and the astrophysical black holes are expected to belong to the Kerr family, obeying the nohair theorems. Alternative theories of gravity or parameterized deviations of GR allow black hole solutions, which have additional parameters other than mass and angular momentum. We analyze a Schwarzschild-like metric, proposed by Johannsen and Psaltis, characterized by its mass and a deformation parameter. We compute the absorption cross section of massless scalar waves for different values of this deformation parameter and compare it with the corresponding scalar absorption cross section of the Schwarzschild black hole. We also present analytical approximations for the absorption cross section in the high-frequency regime. We check the consistence of our results comparing the numerical and analytical approaches, finding excellent agreement.

Transmission of low-energy scalar waves through a traversable wormhole

“…It is well-known that for a spherically symmetric blackhole the zero-frequency limit of the absorption cross section associated with a minimally coupled massless scalar field coincides with the area of its event horizon [41]. See also [42,43]. Equation (57) shows that using the extreme lowenergy scattering data for a massless field the observer O + cannot distinguish between the wormhole and a blackhole with event horizon area A (radius ρ).…”

“…The behavior of the absorption cross section of more general blackholes for low-energy massless scalar fields has been investigated in Refs. [41][42][43].…”

Scattering by deformed black holes

“…It is important to point out that for positive values of the parameter 3 , the line element (3) has only one singularity, located at r = 0, while for negative values of 3 , the line element has an additional singularity at r = | 3 | 1/3 M [12,29]. If the parameter 3 is sufficiently negative, namely 3 ≤ −8, the singularity lies outside ( 3 < −8) or on ( 3 = −8) the event horizon.…”

“…In particular, two processes, namely the absorption and scattering of fundamental fields by BHs, have been studied over the years considering different fields propagating in various BH spacetimes [19][20][21][22][23][24][25][26][27]. More recently, the absorption of massless scalar waves by parameterized BHs has been investigated considering two distinct parametrized static solutions [28,29].…”

Connection between Sinc Approximation for High-Energy Absorption Cross Section and Shadow of Black Holes

“…Consequently, this effective idea of absorption and emission of particles in the strong gravity region gets physicist attentions [10][11][12][13][14][15]. There are stimulating phenomena between the interactions of fields and black holes such as scattering [16,17], emission [18][19][20][21][22][23][24] and absorption [25][26][27][28][29][30][31][32][33][34][35][36][37][38].…”