Tortoise coordinate and Hawking effect in a dynamical Kerr black hole

TL;DR

This paper investigates Hawking radiation from a dynamical Kerr black hole using an improved method, revealing that the temperature varies across the horizon and remains non-zero even in extremal cases.

Contribution

It introduces a new tortoise coordinate transformation to analyze Hawking effect in dynamical Kerr black holes, providing point-by-point temperature calculations.

Findings

Hawking temperature varies across the black hole surface.

Temperature remains non-zero in extremal dynamical black holes.

New coordinate transformation improves analysis accuracy.

Abstract

Hawking effect from a dynamical Kerr black hole is investigated using the improved Damour-Ruffini method with a new tortoise coordinate transformation. Hawking temperature of the black hole can be obtained point by point at the event horizon. It is found that Hawking temperatures of different points on the surface are different. Moreover, the temperature does not turn to zero while the dynamical black hole turns to an extreme one.