Hawking radiation with pure states

TL;DR

This paper proposes a novel quantization approach in quantum field theory in curved spacetime that preserves unitarity in Hawking radiation by representing states as a direct sum of entangled pure states across black hole regions.

Contribution

It introduces a direct-sum QFTCS with geometric superselection rules that maintains unitarity and describes black hole states as pure states, addressing the information loss problem.

Findings

Preserves unitarity in Hawking radiation.

Represents black hole states as pure states in a direct-sum framework.

Maintains entanglement structure across black hole regions.

Abstract

Hawking's seminal work on black hole radiation highlights a critical issue in our understanding of quantum field theory in curved spacetime (QFTCS), specifically the problem of unitarity loss (where pure states evolve into mixed states). In this paper, we examine a recent proposal for a direct-sum QFTCS, which maintains unitarity through a novel quantization method that employs geometric superselection rules based on discrete spacetime transformations. This approach describes a quantum state in terms of components that evolve within geometric superselection sectors of the complete Hilbert space, adhering to the discrete symmetries of a Schwarzschild black hole. Consequently, it represents a maximally entangled pure state as a direct-sum of two components in the interior and exterior regions of the black hole, thereby preserving the unitarity of Hawking radiation by keeping it in the form of pure states.