Comment on `Hawking radiation from fluctuating black holes'

TL;DR

This paper critiques a previous study on how quantum gravitational fluctuations affect Hawking radiation, clarifying gauge issues and proposing ways to correctly compute the spectrum correction.

Contribution

It identifies gauge artifacts in prior calculations of Hawking radiation corrections and suggests methods to properly eliminate divergences for accurate results.

Findings

Previous calculations contained gauge artifacts leading to divergences.

Proper gauge choice can eliminate unphysical divergences.

Clarifies the correct approach to include gravitational fluctuations in Hawking radiation analysis.

Abstract

Takahashi & Soda (2010 Class. Quantum Grav. v27 p175008, arXiv:1005.0286) have recently considered the effect (at lowest non-trivial order) of dynamical, quantized gravitational fluctuations on the spectrum of scalar Hawking radiation from a collapsing Schwarzschild black hole. However, due to an unfortunate choice of gauge, the dominant (even divergent) contribution to the coefficient of the spectrum correction that they identify is a pure gauge artifact. I summarize the logic of their calculation, comment on the divergences encountered in its course and comment on how they could be eliminated, and thus the calculation be completed.