What simplified models say about unitarity and gravitational collapse

TL;DR

This paper reviews quantum models of gravitational collapse, showing that unitarity can be preserved and transient black-white hole pairs may form instead of permanent black holes.

Contribution

It applies Kuchař decomposition to a quantum shell model, demonstrating unitarity and proposing a transient black-white hole pair scenario.

Findings

Quantum collapse can be modeled unitarily.

High-energy shells may form transient black-white holes.

No permanent black hole necessarily results from collapse.

Abstract

This paper is an extended version of a talk at the conference Constrained Dynamics and Quantum Gravity QG99. It reviews some work on the quantum collapse of the spherically symmetric gravitating thin shell of zero rest mass. Recent results on Kucha\v{r} decomposition are applied. The constructed version of quantum mechanics is unitary, although the shell falls under its Schwarzschild radius if its energy is high enough. Rather that a permanent black hole, something like a transient black and white hole pair seems to be created in such a case.