Instanton condensation and a new phase of BPS black holes

TL;DR

This paper investigates a new phase transition in BPS black holes in AdS_5 x S_5, revealing instanton-induced instability and proposing a link to partial deconfinement in the dual field theory.

Contribution

It uncovers an instanton condensation instability in the superconformal index, indicating a new dominant phase and clarifying the phase diagram of BPS black holes.

Findings

Evidence for instanton condensation in the matrix model

Identification of a new dominant phase for small black holes

Connection to partial deconfinement in the dual field theory

Abstract

We analyse the 1/16-BPS superconformal index for BPS black holes at equal charge in $AdS_5 \times S_5$, uncovering evidence for a new instability in the microcanonical ensemble along the small black hole saddle. This is indicated by instanton condensation in the matrix model description of the index. This instability occurs for black holes of radius close to, but below, the scale at which black holes become `small', and implies a new dominant phase in this region. We propose a connection to the partially deconfined phase in the field theory dual description. This would resolve recent confusion about the location of the partially deconfined phase in the BPS phase diagram and promises new avenues for understanding confinement, partial deconfinement, and the encoding of colour degrees of freedom under the holographic map. We also motivate the importance of instantons in partial deconfinement from a matrix model perspective.