Does black-hole evaporation imply that physics is non-unitary, and if so, what must the laws of physics look like? An Essay

TL;DR

This paper explores whether black hole evaporation implies non-unitary physics and discusses recent developments suggesting that quantum gravity might preserve unitarity, challenging traditional views on information loss and locality.

Contribution

It reviews the information loss paradox and recent theoretical advances indicating that quantum gravity could maintain unitarity, potentially resolving the paradox.

Findings

Recent theories suggest unitarity may be preserved in black hole evaporation.

Ideas about locality and semi-classical approximations might be misleading.

Observable consequences of non-unitarity could be circumvented in new models.

Abstract

Stephen Hawking's discovery of black hole evaporation had the remarkable consequence that information is destroyed by a black hole, which can only be accommodated by modifying the laws of quantum mechanics. Different attempts to evade the information loss paradox were subsequently suggested, apparently without a satisfactory resolution of the paradox. On the other hand, the attempting to include non-unitarity into quantum mechanics might lead to laws predicting observable consequences such as nonlocality or violation of energy-momentum conservation; but it may be possibly to circumvent these obstacles. Recent developments seem to require a different view on quantum gravity and suggest that ideas about locality in physics and Hawking's semi-classical approximation are misleading. An accurate description may show unitary evolution and no information loss after all.