Quantum bounce and cosmic recall

TL;DR

This paper demonstrates, using an exactly solvable loop quantum cosmology model, that the universe retains almost complete memory of its previous state across the quantum bounce, with negligible change in fluctuations.

Contribution

It provides an analytical proof that semiclassical states preserve their properties through the quantum bounce in a simplified loop quantum cosmology model.

Findings

Fluctuations across the bounce are bounded by less than 10^{-56}.

The universe maintains near-total recall of its pre-bounce state.

The model supports the idea of a universe with preserved quantum information through the bounce.

Abstract

Loop quantum cosmology predicts that, in simple models, the big bang singularity of classical general relativity is replaced by a quantum bounce. Because of the extreme physical conditions near the bounce, a natural question is whether the universe can retain, after the bounce, its memory about the previous epoch. More precisely, does the universe retain various properties of the state after evolving unitarily through the bounce or does it suffer from some cosmic amnesia as has been recently suggested? Here we show that this issue can be answered unambiguously at least within an exactly solvable model, derived from a small simplification of loop quantum cosmology, for which there is full analytical control on the quantum theory. We show that if there exists a semiclassical state at late times on one side, peaked around a pair of canonically conjugate variables, then there are very strong bounds on the fluctuations on the other side of the bounce, implying semi-classicality. For such a model universe which grows to a size of 1 megaparsec, at late times, the change in relative fluctuations of the only non-trivial observable of the model across the bounce is less than $10^{-56}$ (becoming smaller for universes which grow larger). The universe maintains (an almost) total recall.