Probing Dark Energy with Gravitational Waves
Gravitational wave (GW) astronomy can probe fundamental properties of gravity and provides novel tests of dark energy (DE) models with dynamical fields. The recent measurement of the GW speed following GW170817 is an excellent example of the immense potential available to GWs tests of gravity. I will introduce a theoretical framework for GW propagation in general space-times, present the conditions for anomalous GW speed and classify the theories for DE that remain viable after GW170817. Besides the propagation speed, other effects may provide signatures between the GW emission and the detection, arising both from additional polarizations and non-trivial backgrounds. I will discuss how to compute these effects using our formalism and the potential of these signatures in the quest for the nature of DE.