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