Some remarks on 't Hooft's S-matrix for black holes

TL;DR

This paper critically examines 't Hooft's black hole S-matrix proposal, highlighting its limitations and the implications for semi-classical approximation validity at scales larger than the Planck length.

Contribution

It reveals that the validity of 't Hooft's S-matrix requires semi-classical approximation breakdown at large scales and emphasizes the importance of the centrifugal barrier effect.

Findings

Semi-classical approximation breaks down at scales larger than Planck length.

Centrifugal barrier significantly influences the S-matrix at large transverse distances.

Limitations of 't Hooft's proposal are identified in the context of black hole physics.

Abstract

We discuss the limitations of 't Hooft's proposal for the black hole S-matrix. We find that the validity of the S-matrix implies violation of the semi-classical approximation at scales large compared to the Planck scale. We also show that the effect of the centrifugal barrier on the S-matrix is crucial even for large transverse distances.