Qualitative analysis for viscous cosmologies in a non linear regime of the Israel-Stewart formalism

Abstract We explore the dynamical properties of a cosmological model that includes viscous effects in dark matter sector fluid equations flat Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetime. The bulk are described by non linear extension full Israel-Stewart model, which is causal scheme. allow interchange energy and describe this means interaction term, namely Q . establish system corresponding to Friedmann set associated study stability its critical points. From exploration system, we show appearance point characterizing de Sitter universe within interacting sector. focus our analyse fixed large region parameter space derive linearized solutions around it. These approximate analytical potentially able expansion since they close stationary solution. Within regime with ≠ 0, realize existence regions parameters where stable describes behavior as quintessence, constant phantom like fluids. perform comparison between numerical nearby points regimes also contrast them against ΛCDM fiducial model. find fully favored observations closer concordance due non-zero value j , controls viscosity. In fact, at low redshift values, rate practically indistinguishable from deceleration obtained exhibits transition decelerated accelerated cosmic expansion.