A proposal of the gauge theory description of the small Schwarzschild black hole in AdS$_5\times$S$^5$
Masanori Hanada, Jonathan Maltz
TL;DR
This work proposes a gauge-theory description for the small Schwarzschild black hole in AdS$_5\times$S$^5$ by interpreting a BH as a bound state of eigenvalues of the scalar fields in 4d ${\cal N}=4$ SYM on $\mathbb{R}^{1}\times$S$^3$ and its emission as a reduction in dynamical degrees of freedom. By analyzing the microcanonical ensemble and leveraging the AdS/CFT correspondence for the large BH, the authors derive the energy–temperature relation $E \sim 1/(G_{\rm 10,N} T^7)$ for the small BH, and show that Hagedorn behavior emerges in the strong-coupling regime via long closed strings or winding matrix degrees of freedom. The framework also yields consistent ABJM (11d) black-hole scalings and extends to generic theories with a single characteristic scale, suggesting a universal mechanism where small BHs are just smaller realizations of large BHs in gauge theory language. The results underscore the central role of eigenvalue dynamics in gauge/gravity duality and propose avenues for direct gauge-theory tests, including Monte Carlo simulations and matrix RG approaches, to probe horizon physics and information-related aspects. Overall, the paper provides a coherent gauge-theory narrative linking large and small BHs through dynamical truncation of matrix degrees of freedom and captures key gravity-side expectations in the strongly coupled regime.
Abstract
Based on 4d ${\cal N}=4$ SYM on $\mathbb{R}^{1}\times$S$^3$, a gauge theory description of a small black hole in AdS$_5\times$S$^5$ is proposed. The change of the number of dynamical degrees of freedom associated with the emission of the scalar fields' eigenvalues plays a crucial role in this description. By analyzing the microcanonical ensemble, the Hagedorn behavior of long strings at low energy is obtained. Modulo an assumption based on the AdS/CFT duality for a large black hole, the energy of the small ten-dimensional Schwarzschild black hole $E\sim 1/(G_{\rm 10,N}T^7)$ is derived. A heuristic gauge theory argument supporting this assumption is also given. The same argument applied to the ABJM theory correctly reproduces the relation for the eleven-dimensional Schwarzschild black hole. One of the consequences of our proposal is that the small and large black holes are very similar when seen from the gauge theory point of view.
