Regular Stringy Black Holes?

TL;DR

This paper investigates first-order $$ corrections to massless stringy black holes, showing they can produce regular, geodesically complete spacetimes with horizons and eliminated singularities, highlighting the role of higher curvature terms.

Contribution

It demonstrates that $$ corrections can regularize singular black holes, creating new globally extended solutions with horizons and positive or negative mass regions.

Findings

$$ corrections induce horizons and remove singularities.

The resulting spacetime is geodesically complete.

Negative energy contributions are crucial for these properties.

Abstract

We study the first-order $\alpha'$ corrections to the singular 4-dimensional massless stringy black holes studied in the nineties in the context of the Heterotic Superstring. We show that the $\alpha'$ corrections not only induce a non-vanishing mass and give rise to an event horizon, but also eliminate the singularity giving rise to a regular spacetime whose global structure includes further asymptotically flat regions in which the spacetime's mass is positive or negative. We study the timelike and null geodesics and their effective potential, showing that the spacetime is geodesically complete. We discuss the validity of this solution, arguing that the very interesting and peculiar properties of the solution are associated to the negative energy contributions coming from the terms quadratic in the curvature. As a matter of fact, the 10-dimensional configuration is singular. We extract some general lessons on attempts to eliminate black-hole singularities by introducing terms of higher order in the curvature.