Half-BPS Giants, Free Fermions and Microstates of Superstars

TL;DR

This paper explores the microstate structure of 1/2-BPS states in AdS/CFT, revealing dualities between fermion, giant graviton, and dual-giant configurations, and matching state degeneracies with supergravity geometries.

Contribution

It introduces explicit mappings among fermions, giant gravitons, and dual-giant gravitons, demonstrating a duality that reflects particle-hole symmetry and matching microstate counts with supergravity predictions.

Findings

Duality between giant and dual-giant configurations

Degeneracy of 1/2-BPS states matches between CFT and string theory

Superstar geometry reproduces microstate entropy via Bekenstein-Hawking formula

Abstract

We consider 1/2-BPS states in AdS/CFT. Using the matrix model description of chiral primaries explicit mappings among configurations of fermions, giant gravitons and the dual-giant gravitons are obtained. These maps lead to a `duality' between the giant and the dual-giant configurations which is the reflection of particle-hole duality of the fermion picture. These dualities give rise to some interesting consequences which we study. We then calculate the degeneracy of 1/2-BPS states both from the CFT and string theory and show that they match. The asymptotic degeneracy grows exponentially with the comformal dimension. We propose that the five-dimensional single charge `superstar' geometry should carry this density of states. An appropriate stretched horizon can be placed in this geometry and the entropy predicted by the CFT and the string theory microstate counting can be reproduced by the Bekenstein-Hawking formula up to a numerical coefficient. Similar M-theory examples are also considered.