Holographic covering and the fortuity of black holes
Chi-Ming Chang, Ying-Hsuan Lin
TL;DR
The work introduces a holographic covering framework to classify BPS states in holographic CFTs into monotone and fortuitous categories using supercharge cohomology. It argues that monotone BPS states map to perturbative, smooth horizonless bulk geometries, while fortuitous BPS states account for the majority of black hole microstates and entropy, with fortuitous states vastly outnumbering monotone ones at large N. The authors provide evidence from ${\cal N}=4$ SYM and symmetric product orbifolds by quantizing classical moduli spaces of LLM/LM geometries, recovering finite-N BPS spectra and linking trace relations to the holographic picture. The results suggest a new route to microstate construction and raise open questions about extending the framework to less supersymmetric settings and to continuous-N algebras.
Abstract
We propose a classification of BPS states in holographic CFTs into monotone and fortuitous, based on their behaviors in the large $N$ limit. Intuitively, monotone BPS states form infinite sequences with increasing rank $N$, while fortuitous ones exist within finite ranges of consecutive ranks. A precise definition is formulated using supercharge cohomology. We conjecture that under the AdS/CFT correspondence, monotone BPS states are dual to smooth horizonless geometries, and fortuitous ones are responsible for typical black hole microstates and give dominant contributions to the entropy. We present supporting evidence for our conjectures in the ${\cal N}=4$ SYM and symmetric product orbifolds.
