Analysing dissipative effects in the $\Lambda$CDM model

Understand

In the present paper, the effects of viscous dark matter are analysed within the $\Lambda$CDM model.

• Here we consider bulk viscosity through the Israel-Stewart theory approach, leading to an effective pressure term in the continuity equation that accomplishes for the dissipative effects of the dark matter fluid.
• Then, the corresponding equation for viscosity is solved and a general equation for the Hubble parameter is obtained with the presence of a cosmological constant.
• The existence of de Sitter solutions is discussed, where a wider range of solutions is found in comparison to the $\Lambda$CDM model.