The Unruh vacuum and the in-vacuum in the Reissner-Nordstr\"om spacetime

TL;DR

This paper investigates the relationship between the Unruh vacuum and the in-vacuum in Reissner-Nordstr"om black hole spacetimes, revealing key similarities and differences relevant to black hole evaporation.

Contribution

It provides a detailed analysis of the connection between the Unruh vacuum and the in-vacuum specifically in Reissner-Nordstr"om black hole backgrounds, including extremal cases.

Findings

Identifies similarities between the Unruh and in-vacuum states near the horizon.

Highlights differences in the quantum states for extremal and non-extremal black holes.

Enhances understanding of quantum field behavior in charged black hole spacetimes.

Abstract

The Unruh vacuum is widely used as quantum state to describe black hole evaporation since near the horizon it reproduces the physical state of a quantum field, the so called in-vacuum, in the case the black hole is formed by gravitational collapse. We examine the relation between these two quantum states in the background spacetime of a Reissner-Nordstr\"om black hole (both extremal and not) highlighting similarities and striking differences.