Slow-roll inflation in f(R,T) gravity with a RT mixing term

Che-Yu Chen, Yakefu Reyimuaji, Xinyi Zhang 2022 Phys. Dark Univ. 38 (2022) 101130  

We consider slow-roll inflationary models in a class of modified theories of gravity which contains non-minimal curvature–inflaton couplings, i.e., the f(R,T) gravity, where R is the Ricci scalar and T is the trace of the inflaton energy–momentum tensor. On top of the minimally coupled T that has been widely investigated in the literature, we further include a RT mixing term in the theory. This mixing term introduces non-minimal derivative couplings and plays an important role in inflationary dynamics. Taking chaotic and natural inflation as examples, we find that the predictions for spectral tilt and the tensor-to-scalar ratio are sensitive to the existence of the RT mixing term. In particular, by turning on this mixing term, it is possible to bring chaotic and natural inflation into better agreement with observational data.