Non-singular solutions in f(R, T) gravity coupled with a bulk viscous fluid

In this paper, we have derived exact solutions to the Raychaudhuri equation in the presence of a bulk viscous fluid in f(R, T) modified gravity. We obtained the solutions for two distinct cases: the case of general relativity (GR) and non-GR. We have identified that these solutions can describe a non-singular inflationary Universe, i.e. the Emergent Universe (EU). It is seen that the Einstein static (ES) radius of the EU depends on the viscosity parameters and the parameter (?) associated with the f(R, T) model in consideration. In other words, we found that bulk viscosity plays an effective role in determining the ES radius. Further, we also looked upon the inflationary evolution for the model in terms of the temporal variation of the Equation of State (EoS) parameter of the associated inflaton field in light of the latest BICEP2-Keck-Planck (BKP) data. It is found that the model evolves within the constraints set by the BKP data. We have also investigated whether the general solutions obtained for the model can be used as a possible explanation for the present day accelerated expansion of the Universe, based on the statefinder diagnostics and luminosity distance modulus curve. We found that the solutions obtained in our model are well behaved and approach the ACDM phase. Finally, we examined the late-time behaviour of the model by constraining it using the recent Union2.1 supernova dataset and Hubble data.

Automated summary

In this paper, exact solutions to the Raychaudhuri equation in the presence of a bulk viscous fluid in f(R, T) modified gravity were derived. The obtained solutions for two cases, general relativity (GR) and non-GR, can describe a non-singular inflationary Universe, known as the Emergent Universe (EU). It was found that the Einstein static (ES) radius of the EU depends on viscosity parameters and the parameter associated with the f(R, T) model. Furthermore, the inflationary evolution of the model was studied in relation to the Equation of State (EoS) parameter and found to be consistent with the BICEP2-Keck-Planck (BKP) data.