Non-minimal RT coupling and its impact on inflationary evolution in f(R,T) gravity

We examine inflationary models in the f(R,T) gravity framework where we have a conformal constant and an RT-mixing term apart from an R term. The RT-mixing term introduces non-minimal coupling between gravity and matter. We consider the exponential SUSY potential V(ϕ)=M4(1−e−λϕ/Mpl) and a novel potential V(ϕ)=λMpl4−2αϕ2αsin2⁡(βMplαϕα). With the help of COBE normalization, we constrain values of different parameters and extract the field value at the time of Hubble crossing. The end of inflation is marked by ϵ˜v(ϕi)=1 where ϕi is the field value at the end of inflation. Equipped with these values, we then move on to calculate values of spectral index ns and tensor-to-scalar ratio r. Our predicted values of ns and r fall within their observed values from the Planck 2018 survey and BICEP/Keck array measurement for both potential, making them plausible candidates for the inflationary model. We also display the variation of the tensor-to-scalar ratio and spectral index with the coefficient of RT-mixing term for fixed values of e-fold number. There, we find the existence of two local maxima of ns, which occur at a negative and a positive value of ξ, the coefficient of RT-mixing term. Our analysis finds a significant impact of ξ on values of observables.