2023/03/04 by Nasr Ahmed, Ahmed, Nasr, Kamel, Tarek M.
Earth and Planetary Sciences · Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #Geophysics and Gravity Measurements
paper · pdf · doi:10.48550/arxiv.2303.04076
openalex publication_date 2023/03/04 · openalex created_date 2023/03/10 · openalex updated_date 2026/07/28
This paper investigated two scalar field cosmological models in f(R,T) gravity with cosmic transit and varying cosmological constant Λ(t).The cosmological constant tends to have a tiny positive value in the current epoch.The scalar field pressure pϕ shows a sign reversal for a normal scalar field. For the phantom field, the scalar potential V(ϕ) is negative and the energy density ρϕ=Ek+V takes negative values when the equation of state parameter ωϕ is less than -1. While the weak energy condition WEC implies that the total energy density ρ=∑iρi≥ 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 ρi ≥ 0 and pi+ρi ≥ 0, is not violated but with an instability for the second model at late-times. For a scalar field ϕ, The condition ρϕ+pϕ=ρϕ (1+ωϕ)=2Ek≥ 0 allows for ρϕ<0 if ωϕ<-1. The causality and energy conditions have been discussed for both models. The cosmology in both models was studied using a given function a(t) derived from the desired cosmic behavior, which is the opposite of the traditional view.