Rotating black hole in Rastall theory

Abstract

Due to gravitational lensing effect, a black hole casts a shadow larger than its horizon over a bright background and the shape and size can be calculated. We discuss rotating black holes surrounded by a perfect fluid, namely rotating Rastall black hole, which is characterized by mass M , spin a, field structure parameter N s and the Rastall parameter ψ. Based on a detailed discussion of the photon regions in these space-times, we derive an analytical formula for the shadow of a rotating Rastall black hole. We go on to visualize the shadow of black holes for various values of the parameters. For a given value of parameters, the presence of a positive Rastall parameter ψ enlarges the shadow and reduces its deformation with respect to the one in the Kerr spacetime, while for a negative Rastall parameter ψ, the effect is opposite. Interestingly, for a given value of parameters a and N s , shadows of the black hole, deformed concentric circles with right border becoming significantly more oblate with increase in the parameter ψ and similar effect is seen while increasing N s with a given a and ψ. Further, the deformed circles become larger in these both cases.The shadow of a black hole surrounded by a quintessence matter (ψ = 0) is also included for a comparison. We use the absorption cross section to study the energy emission rate of the black hole in Rastall gravity.

Dynamics of charged and rotating NUT black holes in Rastall gravity

“…Here we presents inner, outer, and cosmological horizon solutions for arbitrary parameter in Table 2, where ω = − 2 3 and ω = −1 denotes the surrounding field for quintessence and cosmological constant, respectively. 12 It shows that some suitable parameters are able to wipe out inner horizon. We can see a detailed behavior of the ∆ function with respect to r in Fig.…”

“…Besides the radial function f (r), we can also solve for the perfect fluid density ρ q (r) from Eqs. (13) and (14) as in 1,12…”

“…The θ dependence might rises because we are working with non-vacuum surrounding and modified theory of gravity. 5,12 From this transformations, we finally to the final result of this section: the Kerr-Newman-NUT black hole in Rastall gravity metric solution in Boyer-Lindquist coordinate,…”

“…The value of ω is chosen specifically to match the common surrounding matters such as: dust field (ω = 0), radiation field (ω = 1/3), and quintessence field (ω = −1/3, −2/3). 12 Hence the Rastall parameter has been chosen arbitrarily to match the solutions. Table 1.…”

Rotating black holes with an anisotropic matter field

“…First, we construct a rotating geometry and then obtain matter field satisfying the Einstein equations. For the first step, we employ the Newman-Janis (NJ) algorithm [17,18,19], which has become popular to study the rotational geometry [20,21,22,23,24,25]. This algorithm generates a rotating geometry from a known static one.…”