Charged spherically symmetric black holes in the Lyra geometry and a preliminary investigation on the overcharging process

Abstract

This paper aims to investigate charged spherically symmetric static black holes in the Lyra geometry, in which a scale function naturally arises in the metric and affine structure of these type of manifolds. In particular, it is utilized the appropriate generalization of General Relativity, the recently proposed Lyra Scalar-Tensor Theory (LyST). The simplest generalization of Maxwell electrodynamics for Lyra manifolds is considered. It is presented an analytic solution for the line element of a Reissner-Nordstr\"om LyST generalization. It is shown that, due to the natural presence of a scale radius, it is possible to have three different extremal charges for positive or negative charge intervals. As a consequence, in natural units, the equality of the mass and charge defined on Lyra manifolds does not give rise to an extremal black hole, which allows the existence of solutions in which the charge is greater than the mass. An analysis with charged test particles indicates that a finite positive Lyra scale radius possibly allows for a violation of the weak cosmic censorship on Lyra manifolds, it is shown that an extremal black hole can be overcharged to the point that the emergence of a naked singularity becomes possible. The same behavior is observed for negative values of the Lyra radius if its absolute value is greater than four times the black hole mass. Notably, this investigation also shows that an eternal black hole can exist for any charge increase if the Lyra scale radius is sufficiently close to some critical values.