Echo of the Quantum Bounce

TL;DR

This paper proposes that quantum gravitational effects from the early universe, especially a quantum bounce, leave lasting signatures in quantum field fluctuations observable today, offering a potential test for quantum gravity theories.

Contribution

It identifies a persistent quantum noise signature from the early universe's quantum bounce, providing a novel observational window into quantum gravity effects.

Findings

Quantum bounce leaves non-damped signatures in quantum noise.

Estimated energy and length scales where quantum effects are relevant.

Potential observational methods to detect quantum gravity signatures.

Abstract

We identify a signature of quantum gravitational effects that survives from the early universe to the current era: Fluctuations of quantum fields as seen by comoving observers are significantly influenced by the history of the early universe. In particular we show how the existence (or not) of a quantum bounce leaves a trace in the background quantum noise that is not damped and would be non-negligible even nowadays. Furthermore, we estimate an upper bound for the typical energy and length scales where quantum effects are relevant. We discuss how this signature might be observed and therefore used to build falsifiability tests of quantum gravity theories.