The trans-Planckian problem as a guiding principle

TL;DR

This paper explores the trans-Planckian problem in Hawking radiation, proposing three possible scenarios for black hole evaporation based on horizon stability and high-energy physics, and suggests pulsations as a Hawking-like emission mechanism.

Contribution

It introduces a framework using the avoidance of the trans-Planckian problem to classify possible black hole evaporation scenarios and analyzes their physical viability.

Findings

Long-lived horizons with superluminal signaling are unstable.

Pulsations near the gravitational radius can produce Hawking-like radiation.

Only three scenarios are consistent with the trans-Planckian avoidance principle.

Abstract

We use the avoidance of the trans-Planckian problem of Hawking radiation as a guiding principle in searching for a compelling scenario for the evaporation of black holes or black-hole-like objects. We argue that there exist only three possible scenarios, depending on whether the classical notion of long-lived horizon is preserved by high-energy physics and on whether the dark and compact astrophysical objects that we observe have long-lived horizons in the first place. Along the way, we find that (i) a theory with high-energy superluminal signalling and a long-lived trapping horizon would be extremely unstable in astrophysical terms and that (ii) stellar pulsations of objects hovering right outside but extremely close to their gravitational radius can result in a mechanism for Hawking-like emission.