Nonlinear charged black hole solution in Rastall gravity

TL;DR

This paper derives a novel spherically symmetric charged black hole solution in Rastall gravity with nonlinear electrodynamics, revealing the influence of the Rastall parameter on spacetime properties, stability, and thermodynamics.

Contribution

It introduces a new black hole solution in Rastall gravity with nonlinear electrodynamics, showing how the Rastall parameter affects the spacetime and thermodynamic stability.

Findings

The solution reduces to Reissner-Nordström in GR limit.

The black hole is thermodynamically stable.

The Rastall parameter is absorbed into the cosmological constant.

Abstract

We show that the spherically symmetric { black hole (BH)} solution of a charged (linear case) field equation of Rastall gravitational theory is not affected by the Rastall parameter and this is consistent with the results presented in the literature. However, when we apply the field equation of Rastall's theory to a special form of nonlinear electrodynamics (NED) source, we derive a novel spherically symmetric BH solution that involves the Rastall parameter. The main source of the appearance of this parameter is the trace part of the NED source, which has a non-vanishing value, unlike the linear charged field equation. We show that the new BH solution is just Anti-de-Sitter Reissner-Nordstr\"om spacetime in which the Rastall parameter is absorbed into the cosmological constant. This solution coincides with Reissner-Nordstr\"om solution in the GR limit, i.e. when Rastall's parameter vanishing. To gain more insight into this BH, we study the stability using the deviation of geodesic equations to derive the stability condition. Moreover, we explain the thermodynamical properties of this BH and show that it is stable, unlike the linear charged case that has a second-order phase transition. Finally, we prove the validity of the first law of thermodynamics.