We propose a new fluid model of dark energy for −1 ≤ ω eff ≤ 0 as an alternative to the generalized Chaplygin gas models. The energy density of dark energy fluid is severely suppressed during barotropic matter dominant epochs, and it dominates the universe evolution only for eras of small redshift. From the perspective of fundamental physics, the fluid is a tachyon field with a scalar potential flatter than that of power-law decelerated expansion. Different from the standard ΛCDM model, the suggested dark energy model claims that the cosmic acceleration at present epoch can not continue forever but will cease in the near future and a decelerated cosmic expansion will recover afterwards.Recent cosmic observations, including Type Ia Supernovae[1, 2], Large Scale Structure (LSS) [3,4,5,6,7,8] and Cosmic Microwave Background (CMB)[9, *
We consider, in normal-gauge Lyra's geometry, evolution of a homogeneous isotropic universe in a gravitational model involving only the standard matter in interaction with a displacement vector field φ µ .Considering both constant and time-dependent displacement vector field we show that the observed cosmic acceleration could be explained without considering an alien energy component with a negative pressure.
In this work, we study the evolution of an isotropic universe in an extended theory of gravity obtained geometrically by transforming the normal-gauge Lyra displacement vector field [Formula: see text] as a complex vectorial function depending on a dynamical scalar field [Formula: see text]. By using the latest observational data, we observe that for [Formula: see text] the universe starts accelerating at the critical scale factor [Formula: see text] which corresponds to a redshift of [Formula: see text]. We also find that the dark energy fluid considered in this model is a generalized fluid with equation of state [Formula: see text].
In this paper, we investigate geometrically the late-time cosmic acceleration in the presence of pressureless matter and when the universe is devoid of matter. The expansion of the universe undergoes an acceleration due to the modification of Riemann manifold and could even evolve into a phantom regime without considering a ghost field. This phantom stage is explained in terms of generalized fluids with inhomogeneous modifications. Cosmological parameters found in this paper are roughly compatible with latest results based on astrophysical data. We also derive the corresponding [Formula: see text]-gravity.
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