Title:Constraints on cosmological viscosity and self interacting dark matter from gravitational wave observations

Abstract:It has been shown that gravitational waves propagate through ideal fluids without experiencing any dispersion or dissipation. However, if the medium has a non-zero shear viscosity $\eta$ , gravitational waves will be dissipated at a rate proportional to $G \,\eta$. We constrain dark matter and dark energy models with non-zero shear viscosity by calculating the dissipation of gravitational waves from GW150914 which propagate over a distance of $410\, $ Mpc through the dissipative fluid and comparing the data with the theoretical prediction. This provides a proof-of-principle demonstration of the fact that future observations gravitational waves at LIGO have the potential of better constraining the viscosity of dark matter and dark energy.