[HEG] Living on the edge: a non-perturbative resolution to the negativity of bulk entropies

Who: Stefano Antonini (UC Berkeley)
When: Tuesday, November 18, 12:30 pm
Where: Broida 3302
Title: Living on the edge: a non-perturbative resolution to the negativity of bulk entropies
Abstract: In this talk, I will discuss two puzzles in JT gravity. In both cases, entropies become negative when naively computed using bulk techniques. In the first puzzle, the one-sided entropy of a two-sided black hole becomes negative in the presence of many matter operator insertions; in the second puzzle, the thermal entropy in pure JT gravity becomes negative at very low temperatures. These puzzles arise when computing annealed (instead of quenched) entropies, corresponding to an incorrect averaging procedure in the dual matrix model. After defining an "intermediate" quantity, the semi-quenched entropy, I will explain how the positivity of entropy can be rescued. From the bulk perspective, both higher-genus topologies and wormhole effects are crucial, and the genus expansion must be re-summed. From the matrix model perspective, the resolution relies on the statistics of eigenvalues near the edge, governed, in different regimes, by the Airy distribution or by eigenvalue instantons.  Along the way, I will describe a new equivalence between many-point correlators in JT gravity with matter and pure JT gravity partition functions at low temperature, and explain its origin from a matrix model perspective.