Might quantum-induced deviations from the Einstein equations detectably affect gravitational wave propagation?

TL;DR

Quantum measurement-like events can cause deviations from Einstein's equations, potentially affecting gravitational wave propagation, and gravitational wave observations could test semi-classical gravity theories.

Contribution

The paper explores how quantum-induced deviations from Einstein's equations might influence gravitational wave signals and proposes using gravitational wave astronomy to test semi-classical gravity.

Findings

Quantum events can produce macroscopically distinct gravitational fields.

Stochastic quantum effects may cause faster decay of gravitational wave coherence.

Detection or non-detection of signals constrains semi-classical gravity models.

Abstract

A quantum measurement-like event can produce any of a number of macroscopically distinct results, with corresponding macroscopically distinct gravitational fields, from the same initial state. Hence the probabilistically evolving large-scale structure of space-time is not precisely or even always approximately described by the deterministic Einstein equations. Since the standard treatment of gravitational wave propagation assumes the validity of the Einstein equations, it is questionable whether we should expect all its predictions to be empirically verified. In particular, one might expect the stochasticity of amplified quantum indeterminacy to cause coherent gravitational wave signals to decay faster than standard predictions suggest. This need not imply that the radiated energy flux from gravitational wave sources differs from standard theoretical predictions. An underappreciated bonus of gravitational wave astronomy is that either detecting or failing to detect predicted gravitational wave signals would constrain the form of the semi-classical theory of gravity that we presently lack.