Phases of 4d Scalar–tensor Black Holes Coupled to Born–infeld Nonlinear Electrodynamics

Abstract

Recent results show that when non-linear electrodynamics is considered the no-scalar-hair theorems in the scalar-tensor theories (STT) of gravity, which are valid for the cases of neutral black holes and charged black holes in the Maxwell electrodynamics, can be circumvented [1,2]. What is even more, in the present work, we find new non-unique, numerical solutions describing charged black holes coupled to non-linear electrodynamics in a special class of scalar-tensor theories. One of the phases has a trivial scalar field and coincides with the corresponding solution in General Relativity. The other phases that we find are characterized by the value of the scalar field charge. The causal structure and some aspects of the stability of the solutions have also been studied. For the scalar-tensor theories considered, the black holes have a single, non-degenerate horizon, i.e., their causal structure resembles that of the Schwarzschild black hole. The thermodynamic analysis of the stability of the solutions indicates that a phase transition may occur.

Slowly rotating neutron and strange stars inR2gravity

“…Moreover the neutron stars can serve as a tool to test the strong field regime of the alternative theories of gravity. As the investigations show, nonlinear effects can appear in alternative theories of gravity when strong fields are considered for both neutron stars and black holes [4][5][6][7], which are not present for weak fields.…”

Orbital and epicyclic frequencies around rapidly rotating compact stars in scalar-tensor theories of gravity

“…Different astrophysical implications of scalarized neutron stars were examined in [9][10][11][12][13][14][15][16][17][18][19]. Similar nonlinear phenomena in STTs are present also in the black hole case [20][21][22][23].…”

A Connection Between Quasinormal Modes and Nonuniqueness of Charged Scalar-Tensor Black Holes

“…STEFANOV (4) (1) Theoretical Astrophysics, Eberhard-Karls University of Tübingen, Tübingen 72076, Germany (2) INRNE, Bulgarian Academy of Sciences, Sofia, Bulgaria (3) Dept. of Theoretical Physics, Sofia University, 1164 Sofia, Bulgaria (4) Dept.…”

“…Actually this is the simplest choice for the coupling function when the scalar-tensor theories are indistinguishable from the general relativity in the weak field regime, but they can deviate significantly in the strong field regime. [1][2][3] The nonlinear electrodynamics we use is the Born-Infeld one, but the results presented here are valid for a much larger class of nonlinear electrodynamics.…”