Revisiting scalar field cosmology with $Λ(t)$ in $f(R,T)$ gravity

Abstract

Two scalar field cosmological models in f (R, T ) gravity with cosmic transit and varying cosmological constant have been investigated. The time-dependent cosmological constant Λ(t) is positive and tends to a very small value at the present epoch. The scalar field pressure p φ shows a sign flipping for normal scalar field. For the phantom field, the scalar potential V (φ) is negative and the energy density ρ φ = E k + V takes negative values when the equation of state parameter ω φ < −1. While the weak energy condition WEC implies that the total energy density ρ = i ρ i ≥ 0, we still can have a negative ρ term as long as the total ρ is positive. In the current work we argue that the WEC, ρ = i ρ i ≥ 0 and p i + ρ i ≥ 0, is not violated. For a scalar field φ, The conditionThe cosmology in both models has been probed using a given function a(t) deduced from the desired cosmic behavior which is the opposite of the conventional viewpoint.