On small black holes, KK monopoles and solitonic 5-branes

TL;DR

This paper reviews and extends the understanding of higher-curvature corrections in superstring configurations involving black holes, monopoles, and branes, highlighting how these corrections and source modifications affect the system's properties and singularities.

Contribution

It provides a detailed analysis of how higher-curvature corrections influence the nature of black holes, monopoles, and branes, including non-perturbative effects and the conditions for regular horizons.

Findings

Higher-curvature corrections do not alter the black hole, soliton, or naked singularity nature when sources are fixed.

Source modifications can change the system's character independently of curvature corrections.

Existence of regular horizon black holes with entropy matching DH states in four dimensions.

Abstract

We review and extend results on higher-curvature corrections to different configurations describing a superposition of heterotic strings, KK monopoles, solitonic 5-branes and momentum waves. Depending on which sources are present, the low-energy fields describe a black hole, a soliton or a naked singularity. We show that this property is unaltered when perturbative higher-curvature corrections are included, provided the sources are fixed. On the other hand, this character may be changed by appropriate introduction (or removal) of sources regardless of the presence of curvature corrections, which constitutes a non-perturbative modification of the departing system. The general system of multicenter KK monopoles and their 5-brane charge induced by higher-curvature corrections is discussed in some detail, with special attention paid to the possibility of merging monopoles. Our results are particularly relevant for small black holes (Dabholkar-Harvey states, DH), which remain singular after quadratic curvature corrections are taken into account. When there are four non-compact dimensions, we notice the existence of a black hole with regular horizon whose entropy coincides with that of the DH states, but the charges and supersymmetry preserved by both configurations are different. A similar construction with five non-compact dimensions is possible, in this case with the same charges as DH, although it fails to reproduce the DH entropy and supersymmetry. No such configuration exists if $d>5$, which we interpret as reflecting the necessity of having a 5-brane wrapping the compact space.