Remarks on matter-gravity entanglement, entropy, information loss and events

TL;DR

This paper discusses the matter-gravity entanglement hypothesis, proposing it as a solution to black hole information loss and suggesting it as a basis for understanding the emergence of classical inhomogeneities from quantum fluctuations.

Contribution

It introduces the matter-gravity entanglement entropy as a candidate for the universe's entropy and explores its implications for cosmology and the nature of events.

Findings

Matter-gravity entanglement entropy may increase monotonically over time.

The hypothesis offers a potential resolution to the black hole information loss puzzle.

A tentative framework for understanding 'events' based on this entropy is proposed.

Abstract

I recall my 'matter-gravity entanglement hypothesis' and briefly review the evidence for it, based partly on its seeming ability to resolve a number of puzzles related to quantum black holes including the black hole information loss puzzle. I point out that, according to this hypothesis, there is a quantity, i.e. the universe's 'matter-gravity entanglement entropy' -- which deserves to be considered the 'entropy of the universe' and which, with suitable initial conditions, will plausibly increase monotonically with cosmological time. In the last section, which is more tentative and raises a number of further puzzles and open questions, I discuss the prospects for a notion of 'events' which 'happen' whose statistical properties are described by this entropy of the universe. It is hoped that such a theory of events may be a step on the way towards explaining how initial quantum fluctuations convert themselves into inhomogeneities in a seemingly classical universe.