Confronting the warm vector inflation in Rastall theory of gravity with Planck 2018 data

Abstract

Abstract The main focus of this manuscript is to explore the effectiveness of Rastall theory of gravity in describing very early epoch of the universe, called cosmic inflation. In this framework, we develop the basic inflationary dynamical equations for flat FRW metric. To find out the exact solutions of inflaton field and corresponding potentials, we start with a basic technique of choosing a known solution of the scale factor, i.e., intermediate and logamediate forms and then extracted the effective potential necessary to support the inflation under slow-roll condition. Via these solutions, we calculate the inflationary observable such as the slow-roll parameters, e-folding number, scalar/tensor power spectra, scalar spectral index and tensor–scalar ratio in both strong and weak dissipative regimes. The recent Planck 2018 data sets bounds for scalar power spectrum, scalar spectral index, n s = 0 . 966 and tensor–scalar ratio, R 0 . 16 . We have plotted graphical trajectories of R − n s by constraining the model parameters, which show that Planck bounds are fully satisfied by Rastall theory of gravity. Hence, this modified gravity theory has ability to describe the early as well as the late-time cosmic eras elegantly.