Cosmic acceleration with tachyon field

Abstract

In this study, we examine two models of the scalar field, that is, a normal scalar field and a tachyon scalar field in F(R, T, X, phi) gravity to describe cosmic acceleration of the universe, where R, T and X are Ricci curvature scalar, trace of energy-momentum tensor and kinetic energy of scalar field phi, respectively. Using the minimal-coupling Lagrangian F(R, T, X, phi) = f (R) beta T-n + f (X, phi), for both the scalar models we obtain a viable cosmological system, where beta and n are real constants. While a normal scalar field gives a system describing expansion from the deceleration to the late-time acceleration, tachyon field together with R-sigma in the system produces a quintessential expansion which is very close to de Sitter point, where we find a new condition 1 < sigma < 1.005 for inflation.