Siberian Federal University

This research paper investigates the dynamics of a Friedmann–Robertson–Walker cosmolog- ical model characterized by perfect fluid pressure and barotropic bulk viscous pressure. By obtaining exact solutions to Einstein’s field equations with a time-varying periodic deceleration parameter, the study reveals periodic behaviour in most parameters, attributed to the influence of a cosine function in the deceleration parameter. The analysis delves into the physical and dynamical implications of this model, particularly highlighting how negative pressure contributes to the late-time expansion of the universe