Phase-space analysis of the viscous fluid cosmological models in the coincident [formula omitted] gravity

Abstract

In this article, we consider a newly proposed parameterization of the viscosity coefficient ζ, specifically ζ=ζ̄0ΩmsH, where ζ̄0=ζ0Ωm0s within the coincident f(Q) gravity formalism. We consider a non-linear function f(Q)=−Q+αQn, where α and n are arbitrary model parameters, which is a power-law correction to the STEGR scenario. We find an autonomous system by invoking the dimensionless density parameters as the governing phase-space variables. We discuss the physical significance of the model corresponding to the parameter choices n=−1 and n=2 along with the exponent choices s=0,0.5, and 1.05. We find that model I shows the stable de-Sitter type or stable phantom type (depending on the choice of exponent s) behavior with no transition epoch, whereas model II shows the evolutionary phase from the radiation epoch to the accelerated de-Sitter epoch via passing through the matter-dominated epoch. Hence, we conclude that model I provides a good description of the late-time cosmology but fails to describe the transition epoch, whereas model II modifies the description in the context of the early universe and provides a good description of the matter and radiation era along with the transition phase.