Showing papers on "Deceleration parameter published in 1988"
TL;DR: It is argued that a number of models in which the energy density of the scalar field red-shifts in a specific manner are studied could reconcile the low dynamical estimates of the mean mass density with the negligibly small spatial curvature preferred by inflation.
Abstract: The cosmological consequences of a pervasive, rolling, self-interacting, homogeneous scalar field are investigated. A number of models in which the energy density of the scalar field red-shifts in a specific manner are studied. In these models the current epoch is chosen to be scalar-field dominated to agree with dynamical estimates of the density parameter, ${\ensuremath{\Omega}}_{\mathrm{dyn}\mathrm{\ensuremath{\sim}}0.2}$, and zero spatial curvature. The required scalar-field potential is ``nonlinear'' and decreases in magnitude as the value of the scalar field increases. A special solution of the field equations which is an attractive, time-dependent, fixed point is presented. These models are consistent with the classical tests of gravitation theory. The E\"otv\"os-Dicke measurements strongly constrain the coupling of the scalar field to light (nongravitational) fields. Nucleosynthesis proceeds as in the standard hot big-bang model. In linear perturbation theory the behavior of baryonic perturbations, in the baryon-dominated epoch, do not differ significantly from the canonical scenario, while the presence of a substantial amount of homogeneous scalar-field energy density at low red-shifts inhibits the growth of perturbations in the baryonic fluid. The energy density in the scalar field is not appreciably perturbed by nonrelativistic gravitational fields, either in the radiation-dominated, matter-dominated, or scalar-field-dominated epochs. On the basis of this effect, we argue that these models could reconcile the low dynamical estimates of the mean mass density with the negligibly small spatial curvature preferred by inflation.
3,948 citations
TL;DR: In this paper, the necessary relations in each model, considering a perfect fluid, were derived by analyzing Einstein, Pryce-Hoyle and Brans-Dicke cosmologies.
Abstract: Berman presented elsewhere a law of variation for Hubble's parameter that yields constant deceleration parameter models of the universe. By analyzing Einstein, Pryce-Hoyle and Brans-Dicke cosmologies, we derive here the necessary relations in each model, considering a perfect fluid.
220 citations
TL;DR: In this article, an anisotropic cosmological model with a Bianchi I metric was obtained, and the interesting features of this model are its simplicity and the easy way we may define overall Hubble and deceleration parameters.
Abstract: Applying laws of the kind previously published by the author for isotropic models, we obtain an anisotropic cosmological model with a Bianchi I metric. The interesting features of this model are its simplicity and the easy way we may define overall Hubble and deceleration parameters.
9 citations