Black string bounce to traversable wormhole

TL;DR

This paper introduces a regular black string solution that can transition into a traversable wormhole by adjusting a parameter, analyzing its regularity, energy conditions, thermodynamics, and particle orbits.

Contribution

It presents a novel regular black string model inspired by Simpson-Visser's method, capable of representing both black holes and wormholes within a unified framework.

Findings

Null energy condition is always violated across the space.

Thermodynamic properties are modified compared to the original black string.

Stable and unstable orbits for particles are analyzed and compared with non-regular solutions.

Abstract

In this work, a regular black string solution will be presented from the method used by Simpson-Visser to regularize the Schwarzschild solution. As in the Simpson-Visser work, in this new black string solution, it is possible to represent both a regular black hole and a wormhole just by changing the value of a parameter "$a$" used in its metric. Tensors and curvature invariants were analyzed to verify the regularity of the solution, as well as the energy conditions of the system. It was found that the null energy condition will always be violated for the entire space. The analysis of the thermodynamic properties of the regular black string was also carried out, in which the modifications generated about the original solution of the black string, were evaluated, specifically, the Hawking temperature, entropy, its thermal capacity, and the Helmholtz free energy. Finally, we investigate the possible stable or unstable circular orbits for photons and massive particles. The results were compared with those of the non-regular black string, seeking to make a parallel with the Simpson-Visser work.