Deceleration parameter

About: Deceleration parameter is a research topic. Over the lifetime, 1776 publications have been published within this topic receiving 89440 citations.

A new class of cosmological models in Lyra geometry

Abstract: FRW models have been studied in the cosmological theory based on Lyra’s geometry. A new class of exact solutions has been obtained by considering a time dependent displacement field for constant deceleration parameter models of the universe.

Dark Energy Models with Variable Equation of State Parameter

Abstract: The dark energy models with variable equation of state parameter ω are investigated by using law of variation of Hubble’s parameter that yields the constant value of deceleration parameter. Here the equation of state parameter ω is found to be time dependent and its existing range for this model is consistent with the recent observations of SN Ia data, SN Ia data (with CMBR anisotropy) and galaxy clustering statistics. The physical significance of the dark energy models have also been discussed.

Influence of structure formation on the cosmic expansion

Abstract: We investigate the effect that the average backreaction of structure formation has on the dynamics of the cosmological expansion, within the concordance model. Our approach in the Poisson gauge is fully consistent up to second order in a perturbative expansion about a flat Friedmann background, including a cosmological constant. We discuss the key length scales which are inherent in any averaging procedure of this kind. We identify an intrinsic homogeneity scale that arises from the averaging procedure, beyond which a residual offset remains in the expansion rate and deceleration parameter. In the case of the deceleration parameter, this can lead to a quite large increase in the value, and may therefore have important ramifications for dark energy measurements, even if the underlying nature of dark energy is a cosmological constant. We give the intrinsic variance that affects the value of the effective Hubble rate and deceleration parameter. These considerations serve to add extra intrinsic errors to our determination of the cosmological parameters, and, in particular, may render attempts to measure the Hubble constant to percent precision overly optimistic.

Curvature force and dark energy

Abstract: A curvature self-interaction of the cosmic gas is shown to mimic a cosmological constant or other forms of dark energy, such as a rolling tachyon condensate or a Chaplygin gas. Any given Hubble rate and deceleration parameter can be traced back to the action of an effective curvature force on the gas particles. This force self-consistently reacts back on the cosmological dynamics. The links between an imperfect fluid description, a kinetic description with effective antifriction forces and curvature forces, which represent a non-minimal coupling of gravity to matter, are established.

A holographic model of dark energy and the thermodynamics of a non-flat accelerated expanding universe

Abstract: Motivated by recent results on non-vanishing spatial curvature [1] we employ a holographic model of dark energy to investigate the validity of the first and second laws of thermodynamics in a non-flat (closed) universe enclosed by the apparent horizon RA and the event horizon measured from the sphere of the horizon named L. We show that for the apparent horizon the first law is roughly respected for different epochs while the second law of thermodynamics is respected, while for L as the system's IR cut-off the first law is broken and the second law is respected for the special range of the deceleration parameter. It is also shown that for the late-time universe L is equal to RA and the thermodynamic laws hold when the universe has non-vanishing curvature. Defining the fluid temperature as being proportional to the horizon temperature the range for the coefficient of proportionality is obtained, provided that the generalized second law of thermodynamics holds.