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

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 $(μ,ν)$ 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.