Arrow of time in a recollapsing quantum universe

TL;DR

This paper explores how quantum effects influence the arrow of time in a recollapsing universe, suggesting a reversal of time direction near classical turning points and implications for horizons and information paradoxes.

Contribution

It demonstrates that the Wheeler-DeWitt equation allows for a reversed arrow of time in recollapsing universes, with quantum effects enabling consistency across classical turning points.

Findings

Quantum effects facilitate time arrow reversal at turning points.

Collapsing matter begins re-expanding before horizon formation.

No mass inflation or information loss paradox occurs.

Abstract

We show that the Wheeler-DeWitt equation with a consistent boundary condition is only compatible with an arrow of time that formally reverses in a recollapsing universe. Consistency of these opposite arrows is facilitated by quantum effects in the region of the classical turning point. Since gravitational time dilation diverges at horizons, collapsing matter must then start re-expanding ``anticausally" (controlled by the reversed arrow) before horizons or singularities can form. We also discuss the meaning of the time-asymmetric expression used in the definition of ``consistent histories". We finally emphasize that there is no mass inflation nor any information loss paradox in this scenario.