Finite $N$ black hole cohomologies
Jaehyeok Choi, Sunjin Choi, Seok Kim, Jehyun Lee, Siyul Lee
TL;DR
The work tackles finite-$N$ black hole microstates in $\mathcal{N}=4$ SYM by formulating the problem in terms of $Q$-cohomologies of $1/16$-BPS operators and exploiting a BMN truncation to render calculations tractable. It develops strategies to separate graviton from non-graviton cohomologies, computes the graviton index via eigenvalue and Gröbner-basis methods, and identifies non-graviton cohomologies by analyzing the index, including an explicit SU(3) threshold cohomology at $j=24$. The findings reveal structured towers, partial no-hair phenomena, and black-hole-like entropy growth in the BMN sector at large $N$, suggesting rich finite-$N$ microstate structure and guiding future exact index computations at larger $N$. These insights offer a path toward understanding black hole microstates in AdS/CFT through controlled, finite-$N$ $Q$-cohomology constructions and their spectral organization.
Abstract
We study new cohomologies for the BPS operators of the $\mathcal{N}=4$ Yang-Mills theory with $SU(3)$ and $SU(4)$ gauge groups, to better understand the black hole microstates. We first study the index of these black hole operators and identify their apparent threshold levels. For $SU(3)$, we find many towers of states and partial no-hair behaviors. We explicitly construct the threshold cohomology in the $SU(3)$ theory. We study throughout this paper a subsector of the field theory corresponding to the BMN matrix theory. We also argue that the BMN sector exhibits a black hole like entropy growth at large $N$.
