Singularities of thermal correlators at strong coupling

TL;DR

This paper investigates the singularities in thermal correlators within conformal field theories at strong coupling, revealing new bulk-induced singularities and their resolution via tidal effects in holographic models.

Contribution

It identifies and analyzes new singularities in thermal correlators caused by bulk null geodesics and demonstrates their resolution through string worldsheet calculations in the holographic setting.

Findings

New singularities arise from bulk null geodesics around the photon sphere.

Tidal effects resolve these singularities in the string worldsheet analysis.

Discussion of singularities in asymptotically flat black hole geometries.

Abstract

We analyze the singularities of the two-point function in a conformal field theory at finite temperature. In a free theory, the only singularity is along the boundary light cone. In the holographic limit, a new class of singularities emerges since two boundary points can be connected by a nontrivial null geodesic in the bulk, encircling the photon sphere of the black hole. We show that these new singularities are resolved by tidal effects due to the black hole curvature, by solving the string worldsheet theory in the Penrose limit. Singularities in the asymptotically flat black hole geometry are also discussed.