Conformally rescaled spacetimes and Hawking radiation

TL;DR

This paper investigates how Hawking radiation properties, such as horizon location and temperature, transform under conformal rescaling of spacetime metrics, revealing that horizon location is not invariant but temperature transforms simply.

Contribution

It provides a detailed analysis of Hawking radiation derivations in conformally rescaled spacetimes, clarifying the behavior of horizon location and temperature under such transformations.

Findings

Hawking radiation production is not always linked to the trapping horizon.

Horizon location varies under conformal transformations.

Hawking temperature remains invariant for asymptotic observers when the conformal factor approaches unity.

Abstract

We study various derivations of Hawking radiation in conformally rescaled metrics. We focus on two important properties, the location of the horizon under a conformal transformation and its associated temperature. We find that the production of Hawking radiation cannot be associated in all cases to the trapping horizon because its location is not invariant under a conformal transformation. We also find evidence that the temperature of the Hawking radiation should transform simply under a conformal transformation, being invariant for asymptotic observers in the limit that the conformal transformation factor is unity at their location.