Cosmological parameters of the F(R,T,X,Phi)-gravity model

Abstract

In this paper, we study an extended modified F(R,X,Phi) gravity theory applied to the homogeneously isotropic Friedmann–Robertson–Walker metric. Based on the obtained field equations, we analyze the solutions, including additional conditions such as the Monge–Ampère equation. It is shown that for certain parameter values, the model leads to a regime corresponding to the quasi-de Sitter expansion of the Universe. We compare the theoretical results with observational data from the Planck 2018 mission, including the Hubble constant, dark energy density, spectral index, primordial fluctuation amplitude, and the tensor-to-scalar mode ratio. We show that the model is in natural agreement with cosmological observations of both the late and early Universe, providing the suppression of tensor perturbations and the correct spectral tilt. The results obtained confirm the physical consistency and observational compatibility of this modified gravity model.