Abstract
We consider a model of dark energy (DE) which contains three terms (one proportional to the squared Hubble parameter, one to the first derivative, and one to the second derivative with respect to the cosmic time of the Hubble parameter) in the light of the f(R,T)=μR+νT modified gravity model, with μ and ν being two constant parameters. R and T represent the curvature and torsion scalars, respectively. We found that the Hubble parameter exhibits a decaying behavior until redshifts z≈-0.5 (when it starts to increase) and the time derivative of the Hubble parameter goes from negative to positive values for different redshifts. The equation of state (EoS) parameter of DE and the effective EoS parameter exhibit a transition from ω<-1 to ω>-1 (showing a quintom-like behavior). We also found that the model considered can attain the late-time accelerated phase of the universe. Using the statefinder parameters r and s, we derived that the studied model can attain the ΛCDM phase of the universe and can interpolate between dust and ΛCDM phase of the universe. Finally, studying the squared speed of sound vs2, we found that the considered model is classically stable in the earlier stage of the universe but classically unstable in the current stage.
Highlights
The late-time accelerated expansion of the universe [1, 2] is a major challenge for cosmologists
We have considered a recently proposed model of energy density of dark energy (DE) which depends on three terms, one proportional to the squared Hubble parameter H, one proportional to the time derivative of H, and one proportional to the second time derivative of H interacting with pressureless DM in the framework of the f(R, T) modified gravity theory for the special model given by f(R, T) = μR + ]T, where μ and ] represent two constants
The time derivative of the Hubble parameter, that is, Ḣ, shows a transition from negative to positive values for different values of the redshift z according to the value of ε considered
Summary
The late-time accelerated expansion of the universe (which is well-established from different cosmological observations) [1, 2] is a major challenge for cosmologists. For good reviews on DE see [4,5,6]. Nojiri and Odintsov [7] described the reasons why modified gravity approach is extremely attractive in the applications for late accelerating universe and DE. Another good review on modified gravity was made by Clifton et al [8]. Many different theories of modified gravity have been recently proposed: some of them are f(R) (with R being the Ricci scalar curvature) [9, 10], f(T) (with T being the torsion scalar) [11,12,13,14], Horava-Lifshitz [15, 16], and
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