Speaker
Description
Self-Interacting Dark Matter (SIDM) is a lucrative candidate to address the small-scale issues faced by the collisionless cold dark matter. We propose that the collisional nature of the SIDM particles on the small scales can lead to dissipative effects. We estimate the shear and bulk viscosity of SIDM using the kinetic theory in relaxation time approximation. We investigate the effect of SIDM dissipation on cosmic evolution and find that $ \sigma/m $ constraints on SIDM from astrophysical data provide sufficient viscosity to account for the observed cosmic acceleration. Furthermore, we also found that the energy dissipation from the viscous SIDM fluid was small at a large redshift but became important at the recent epochs of cosmic evolution (when the Universe is dominant by the non-linear structure). Consequently, the viscous SIDM fluid can also explain the low redshift cosmological observations without any need for the extra dark energy component. The entire analysis is independent of any specific particle physics motivated model for SIDM.
