Essential and inessential features of Hawking radiation

TL;DR

This paper presents a minimalist derivation of Hawking radiation, showing that quantum physics and a slowly evolving apparent horizon are sufficient, without relying on Einstein equations or Bekenstein entropy.

Contribution

It simplifies the derivation of Hawking radiation by identifying the essential features needed, removing unnecessary assumptions and physical concepts.

Findings

Hawking radiation can be derived without Einstein equations.

A slowly evolving apparent horizon suffices for the derivation.

Bekenstein entropy is not necessary in the derivation.

Abstract

There are numerous derivations of the Hawking effect available in the literature. They emphasise different features of the process, and sometimes make markedly different physical assumptions. This article presents a ``minimalist'' argument, and strips the derivation of as much excess baggage as possible. All that is really necessary is quantum physics plus a slowly evolving future apparent horizon (*not* an event horizon). In particular, neither the Einstein equations nor Bekenstein entropy are necessary (nor even useful) in deriving Hawking radiation.