Bulk viscous late acceleration under near equilibrium conditions in f(R, T) gravity with mixed matter

TL;DR

This paper proposes a modified gravity model with mixed dark matter components that explains late universe acceleration without a cosmological constant, satisfying near equilibrium conditions and fitting observational data.

Contribution

It introduces a new $f(R,T)$ gravity model with viscous and inviscid dark matter components that achieves late acceleration without requiring a cosmological constant.

Findings

Model predicts late acceleration while satisfying NEC.

Fits observational data from Supernovae and Hubble measurements.

Provides estimated cosmological parameters consistent with observations.

Abstract

Various studies have shown that the late acceleration of the universe can be caused by the bulk viscosity associated with dark matter. But recently, it was indicated that a cosmological constant is essential for maintaining Near Equilibrium Conditions (NEC) for the bulk viscous matter during the accelerated expansion of the universe. In the present study, we investigate a model of the universe composed of mixed dark matter components, with viscous dark matter (vDM), and inviscid cold dark matter (CDM) as it's constituents, in the context of $f(R,T)$ gravity and showed that the model predicts late acceleration by satisfying NEC throughout the evolution, without cosmological constant. We have also compared the model predictions with combined Type Ia Supernovae and observational Hubble data sets and thereby determined the estimated values of different cosmological parameters.