# Quantum gravity and gravitational-wave astronomy

## TL;DR

This paper explores how gravitational-wave observations can detect signatures of quantum gravity, focusing on effects like dimensional flow and modifications to the Planck mass, providing new constraints on quantum-gravity theories.

## Contribution

It introduces a framework to test quantum gravity effects through GW data, including the first constraints from actual LIGO data and simulated LISA sources.

## Key findings

- GW observations can constrain quantum-gravity parameters more strongly than some traditional tests.
- Dimensional flow effects can be tested with current and future GW detectors.
- Specific quantum-gravity models can be constrained or distinguished using GW data.

## Abstract

We investigate possible signatures of quantum gravity which could be tested with current and future gravitational-wave (GW) observations. In particular, we analyze how quantum gravity can influence the GW luminosity distance, the time dependence of the effective Planck mass and the instrumental strain noise of interferometers. Using both model-dependent and model-independent formulae, we show that these quantities can encode a non-perturbative effect typical of all quantum-gravity theories, namely the way the dimension of spacetime changes with the probed scale. Effects associated with such dimensional flow might be tested with GW observations and constrained significantly in theories with a microscopically discrete spacetime geometry, more strongly than from propagation-speed constraints. Making use of public LIGO data as well as of a simulated higher-redshift LISA source, we impose the first, respectively, actual and mock constraints on quantum-gravity parameters affecting the GW luminosity distance and discuss specific theoretical examples. If also the Newtonian potential is modified but light geodesics are not, then solar-system bounds may be stronger than GW ones. Yet, for some theories GW astronomy can give unique information not available from solar-system tests.