TPPC weekly seminar (in-person): Antonio Enea Romano - “The effects of dark energy on the propagation of gravitational waves”

Wednesday 18 Jan 2023, 12:30 → 14:00 Europe/London

Strand Building, S7.06

Speaker: Antonio Enea Romano

Title: The effects of dark energy on the propagation of gravitational waves

Abstract: Modeling dark energy as an effective stress-energy-momentum tensor (EST) in the Einstein's equations, we derive a model independent equation for the propagation of gravitation waves (GW) in terms of an effective GW speed cT related to the anisotropy of the EST, showing that it can depend on time, space, and polarization. A similar result is derived in momentum space, in terms of an appropriately defined momentum effective speed c~T. The friction term depends on c~′T/c~T, and can be expressed in terms of an effective frequency dependent scale factor. The corresponding effective Lagrangian density is derived in Einstein's and Jordan's frame, showing that the effects of higher order interaction terms are encoded in the frequency and polarization dependency of the c~T. Introducing an appropriate effective metric depending on cT, the GW propagation equation can be written in terms of the covariant d'Alambert operator. The modification of the friction term induces a frequency and polarization dependent difference between GW and electromagnetic luminosity distance, given by the relation dGWL(z)=c~T(z)dEML(z). We discuss the implications for constraining dark energy models and modified gravity theories with GW luminosity distance observations, using bright and dark sirens.