Temporal contribution to gravitational WKB-like calculations

TL;DR

This paper reveals a previously overlooked temporal contribution in gravitational WKB-like calculations of Hawking radiation, which is essential for obtaining the correct temperature and applies broadly to horizons where time signature changes.

Contribution

It identifies a new temporal contribution in quasi-classical calculations of gravitational radiation, highlighting subtleties not present in standard quantum tunneling approaches.

Findings

Temporal contribution is crucial for correct radiation temperature.

Method applies to any gravitational background with horizon-induced time signature change.

Enhances understanding of semi-classical methods in quantum gravity.

Abstract

Recently, it has been shown that the radiation arising from quantum fields placed in a gravitational background (e.g. Hawking radiation) can be derived using a quasi-classical calculation. Here we show that this method has a previously overlooked temporal contribution to the quasi--classical amplitude. The source of this temporal contribution lies in different character of time in general relativity versus quantum mechanics. Only when one takes into account this temporal contribution does one obtain the canonical temperature for the radiation. Although in this letter the specific example of radiation in de Sitter space--time is used, the temporal contribution is a general contribution to the radiation given off by any gravitational background where the time coordinate changes its signature upon crossing a horizon. Thus, the quasi--classical method for gravitational backgrounds contains subtleties not found in the usual quantum mechanical tunneling problem.