Warm Viscous Inflation Inspired by Modified Chaplygin Gas within Rastall Theory of Gravity

Abstract

This thesis is a contribution to study the effectiveness of Rastall gravity (RG) to discuss warm viscous inflation inspired by modified Chaplygin gas. The mat- ter contents of our cosmos are taken to be standard scalar field (ϕ) and radiation within flat Friedman-Robertson-Walker (FRW) geometry. We establish the cur- rent model using intermediate form of scale factor and calculate the analytic solution of inflaton, effective potential V (ϕ) necessary to inflate the universe and entropy density S under slow-roll limit. The further work in this paper is restricted to high dissipative regime, taking constant and variable dissipa- tive (Γ) and viscous coefficients (ξ). The evaluated exact solutions are the main source in developing the inflationary observable like scalar/tensor power spec- tra, scalar/tensor spectral indices, tensor to scalar ratio and running of scalar spectral index for our model. The model parameters as well as additional the- ory parameter λ are constrained to check the compatibility of RG with Planck 2018 data via R − ns and αs − ns trajectories. We conclude that RG along with modification of Chaplygin gas model can lead to significant changes in the early universe.