A dark energy model alternative to generalized Chaplygin gas

Abstract

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, *

Challenging bulk viscous unified scenarios with cosmological observations

“…29 −0.17 (68% CL) whilst from the remaining datasets, the mean values of m are negative with increased significance when more datasets are considered: m = −0.32 +0. 16 −0.21 (68% CL, CMB+CC), m = −0.56 +0.25 −0.12 (68% CL, CMB+Pantheon), m = −0.51 +0.14 −0.09 (68% CL, CMB+Pantheon+CC). From all the analyses, we find that m = 0 at more than 68% CL, that means the observation data are in strong agreement of a nonzero bulk viscosity in the universe sector.…”

“…Theoretically, there is no objection to consider such UDM scenarios since the nature of dark sector could be anything. In the context of Einstein's gravitational theory, such UDM scenarios are described by an equation of state p = f (ρ), where p and ρ, are respectively the pressure and energy density of the UDM fluid and f is any analytic function of the energy density, ρ (one can quickly recall the Chaplygin gas [4,5,6,7,8,9,10,11,12,13,14,15] and other unified cosmologies [16,17,18] in this context). Sometimes, these UDM scenarios are also studied in the form of p = g(H) where g is any analytic function of H, the Hubble rate of the Friedmann-Lemaître-Robertson-Walker (FLRW) universe which is the well known geometrical description of our universe in the large scale and in this present work we have considered such geometrical configuration.…”

Cosmological constraints on alternative model to Chaplygin fluid revisited

“…As we mention previously, while most of these models postulate two dark components, the Chaplygin gas [17] and the generalized Chaplygin-like gas (GCG) [18][19][20] propose an unique dark fluid to describe the dynamics of the dark sector with an equation of state p = −Aρ −n [21] where 0 < n ≤ 1 and A is defined as positive 1 . In the inflationary model context, another elliptic Chaplygin generalization has been proposed through the Hamilton-Jacobi formalism [22].…”

“…al. [1], consisting on a modification of a perfect fluid, to explain the dynamics of dark matter and dark energy at cosmological scales immerse in a flat or curved universe. Adopting properties similar to a Chaplygin gas, the proposed model is a mixture of dark matter and dark energy components parameterized by only one free parameter denoted as µ.…”

Cosmic acceleration in unimodular gravity

“…The first way implies that approximately sixty nine [3] percent of our universe is filled with something we do not know yet. Following this line of thought, some of the most studied models are: the cosmological constant (CC) [4], phantom and quintessence fluids [5,6], generalized perfect fluids [7], etc. The second possibility considers that the Einstein's theory of gravitation must be changed in order to explain this gravitational anomaly.…”