Newman-Janis algorithm's application to regular black hole models

TL;DR

This paper investigates how the Newman-Janis algorithm can generate Kerr-like black hole solutions from regular static solutions with scalar fields, highlighting discrepancies in Einstein's equations within certain regions.

Contribution

It demonstrates the application of the Newman-Janis algorithm to a scalar field-based regular black hole, revealing limitations and discrepancies in Einstein's equations.

Findings

The algorithm produces a Kerr-like black hole with regularity.

Discrepancies in Einstein's equations occur in a small domain.

Outside this domain, the solution matches standard Kerr spacetime.

Abstract

We examine the Newman-Janis algorithm's application to an exact regular static solution sustained by a minimally coupled scalar field with a non-standard kinetic term. Although coordinate complexification leads to a regular Kerr-like black hole, we are facing discrepancies in Einstein's equations in a fairly small domain, for which the regularizing parameter is responsible. Outside this most intriguing region, the geometry is nothing but the standard Kerr spacetime.