A toy model for representing regular black holes at the black string style

TL;DR

This paper constructs a regular four-dimensional black hole model within a five-dimensional black string framework, establishing geometric and physical relations consistent with known theories and deriving thermodynamic properties.

Contribution

It introduces a novel regular black hole model in a five-dimensional black string setting with specific topological and geometric constraints, aligning 4D and 5D equations of motion.

Findings

The 5D geometry is regular and topologically distinct from traditional Kaluza-Klein black strings.

The relation between 4D and 5D Newton constants matches previous literature.

The first law of thermodynamics is verified with correct temperature and entropy values.

Abstract

We provide a way of representing a four dimensional regular black hole geometry at the black string style. We enunciate a list of constrains in order to that the complete five dimensional geometry to be regular. Following these constraints were constructed both the four and the five dimensional geometries. The assumptions used to solve the equations of motion suggest a relation between the $4D$ and the $5D$ Newton constants, which coincides with relations previously showed in the literature. Furthermore, the $(\mu,\nu)$ components of the five dimensional equations of motion adopt the form of the four dimensional equations of motion. Also, the five dimensional conservation equation adopts the form of the four dimensional conservation equation. At the origin the topology of the five dimensional geometry corresponds to the product between the four dimensional de--Sitter space--time and $S^1$ with $z$ compact. This latter differs from the Kaluza-Klein black string, where, at the origin the topology corresponds to the product between the Schwarzschild singularity and $R(S^1)$ for $z$ non compact (compact). The topology of the complete five dimensional geometry corresponds to $S^2 \times S^1$. At the infinity of the radial coordinate the topology corresponds to the product between Minkowski and $S^1$. At the induced four dimensional geometry we compute the first law of thermodynamics with the correct values of temperature and entropy.