Quantum Gravity and Non-unitarity in Black Hole Evaporation

TL;DR

This paper explores how quantum gravitational effects influence black hole evaporation, revealing that near the Planck scale, unitarity can be violated in the non-gravitational sector, impacting the information loss paradox.

Contribution

It introduces a semiclassical expansion of the Wheeler-DeWitt equation showing unitarity violation during black hole evaporation's final stage.

Findings

Unitarity is explicitly violated near the Planck regime.

Pure states remain pure despite non-unitarity effects.

Non-pure states become more pure in the non-gravitational sector.

Abstract

We discuss the relevance of quantum gravitational corrections to the functional Schr\"odinger equation for the information loss paradox in black hole evaporation. These corrections are found from the Wheeler-DeWitt equation through a semiclassical expansion scheme. The dominant contribution in the final evaporation stage, when the black hole approaches the Planck regime, is a term which explicitly violates unitarity in the non-gravitational sector. While pure states remain pure, there is an increase in the degree of purity for non-pure states in this sector. This result holds irrespective of whether full quantum gravity respects unitarity or not.