Structure formation with causal bulk viscosity

Dissipative features of dark matter affect its clustering properties and could lead to observable consequences for the evolution of large--scale structure. We analyse the evolution of cold dark matter density perturbations allowing for the possibility of bulk viscous pressure in a causal dissipative theory. Our analysis employs a Newtonian approximation for cosmological dynamics and the transport properties of bulk viscosity are described by the Israel--Stewart theory. We obtain a third order evolution equation for density perturbations. For some parameter values the density contrast can be suppressed compared to results obtained in the $Λ$CDM scenario. For other values causal bulk viscous dark matter can exhibit an enhancement of clustering. 5 pages, 1 figure, accepted for publication in The Proceedings of SAIP2017, the 62nd Annual Conference of the South African Institute of Physics