Supersymmetric Black Holes in $N=8$ Supergravity

TL;DR

This paper investigates how extremal dilaton black hole solutions embed into N=4 and N=8 supergravity theories, revealing relations between the parameter a and supersymmetry preservation, and highlighting duality connections.

Contribution

It identifies the embedding patterns of black hole solutions in N=8 supergravity and their supersymmetry properties, showing the role of dualities and the special case of dyonic embeddings.

Findings

All embeddings in N=8 have the same unbroken supersymmetries for a given solution.

The parameter a influences supersymmetry in N=8 but not in N=4.

Dyonic a=0 solution breaks all supersymmetries in both theories.

Abstract

We study the embedding of extreme (multi-) dilaton black hole solutions for the values of the parameter $a=\sqrt{3},1,1/\sqrt{3},0$ in $N=4$ and $N=8$ four-dimensional supergravity. For each black hole solution we find different embeddings in $N=4$ supergravity which have different numbers of unbroken supersymmetries. When embedded in $N=8$ supergravity, all different embeddings of the same solution have the same number of unbroken supersymmetries. Thus, there is a relation between the value of the parameter $a$ and the number of unbroken supersymmetries in $N=8$ supergravity, but not in $N=4$, and the different embeddings must be related by dualities of the $N=8$ theory which are not dualities of the $N=4$ theory. The only exception in this scheme is a {\it dyonic} embedding of the $a=0$ black-hole solution which seems to break all supersymmetries both in the $N=4$ and in the $N=8$ theories.