A fixed point formula for the index of multi-centered N=2 black holes

TL;DR

This paper introduces a formula to compute the moduli-dependent contribution of multi-centered BPS black hole solutions to the total index, using localization techniques to analyze fixed points in supergravity configurations.

Contribution

It provides a novel fixed point formula for multi-centered black hole indices, incorporating both scaling and non-scaling solutions with a minimal modification hypothesis.

Findings

Refined index computed via localization methods.

Fixed point contributions determined by a minimal modification hypothesis.

Applicable to both scaling and non-scaling multi-centered solutions.

Abstract

We propose a formula for computing the (moduli-dependent) contribution of multi-centered solutions to the total BPS index in terms of the (moduli-independent) indices associated to single-centered solutions. The main tool in our analysis is the computation of the refined index Tr(-y)^{2J_3} of configurational degrees of freedom of multi-centered BPS black hole solutions in N=2 supergravity by localization methods. When the charges carried by the centers do not allow for scaling solutions (i.e. solutions where a subset of the centers can come arbitrarily close to each other), the phase space of classical BPS solutions is compact and the refined index localizes to a finite set of isolated fixed points under rotations, corresponding to collinear solutions. When the charges allow for scaling solutions, the phase space is non-compact but appears to admit a compactification with finite volume and additional non-isolated fixed points. We give a prescription for determining the contributions of these fixed submanifolds by means of a `minimal modification hypothesis', which we prove in the special case of dipole halo configurations.