Quantum gravity and gravitational-wave astronomy

We review the present status of quantum-gravity phenomenology in relation to gravitational waves (GWs). The topic can be approached from two direction, a model-dependent one and a model-independent one. In the first case, we introduce some among the most prominent cosmological models embedded in theories of quantum gravity, while in the second case we point out certain common features one finds in quantum gravity. Three cosmological GW observables can be affected by perturbative as well as non-perturbative quantum-gravity effects: the stochastic GW background, the propagation speed of GWs and the luminosity distance of GW sources. While many quantum-gravity models do not give rise to any observable signal, some predict a blue-tilted stochastic background or a modified luminosity distance, both detectable by future GW interferometers. We conclude that it is difficult, but still possible, to test quantum gravity with GW observations.