Evaporation of large black holes in AdS: coupling to the evaporon

TL;DR

The paper introduces a toy model to simulate evaporation of large AdS black holes by coupling a bulk scalar to an evaporon living in an extra dimension, thereby making the AdS boundary partially absorptive. It develops the necessary holographic renormalization via counterterms for two conformal dimensions, analyzes the resulting interface scattering, and derives a closed-form transmission coefficient that governs energy leakage into the external sector. The findings reveal a resonant-like dependence of transmission on frequency and provide a framework to estimate evaporation rates as a gray-body factor within the AdS/CFT context. This approach offers a concrete mechanism to address the information paradox in AdS by allowing controlled energy transfer to an external sector, while highlighting the role of boundary conditions and renormalization in holographic setups.

Abstract

Large black holes in an asymptotically AdS spacetime have a dual description in terms of approximately thermal states in the boundary CFT. The reflecting boundary conditions of AdS prevent such black holes from evaporating completely. On the other hand, the formulation of the information paradox becomes more stringent when a black hole is allowed to evaporate. In order to address the information loss problem from the AdS/CFT perspective we then need the boundary to become partially absorptive. We present a simple model that produces the necessary changes on the boundary by coupling a bulk scalar field to the evaporon, an external field propagating in one extra spatial dimension. The interaction is localized at the boundary of AdS and leads to partial transmission into the additional space. The transmission coefficient is computed in the planar limit and perturbatively in the coupling constant. Evaporation of the large black hole corresponds to cooling down the CFT by transferring energy to an external sector.