Early-Universe and Evolution of the Present Universe: Exact Solution Models

Koijam Manihar Singh,Kangujam Priyokumar Singh,Thiyam Jairam Singh

doi:10.4236/jmp.2011.28096

Abstract

The evolution of the Robertson-Walker type universes consisting of radiating perfect fluid distribution coupled with zero-mass scalar field in which the gravitational parameter G varies with cosmic time t are studied. Unified descriptions of the early evolution of the universe consisting of different phases are investigated. The different properties of the cosmological solutions are discussed and the physical behaviour of the model universes during the radiation-dominated era and also during the big bang scenario are studied. Here we obtain models which are geometrically closed and are thereby ever expanding and evolve from rest from a non-singular hot origin with maximum (finite) energy density and temperature and a small minimum (non-zero) gravitational coupling G.

Highlights

Though it is generally accepted that the Newtonian constant of gravity G plays the role of a coupling constant between geometry and matter in the Einstein field equations, it appears natural to look at this constant as a function of time in an evolving universe
The evolution of the Robertson-Walker type universes consisting of radiating perfect fluid distribution coupled with zero-mass scalar field in which the gravitational parameter G varies with cosmic time t are studied
We study the effects of incorporating a zero-mass scalar field which is operative during an instantaneous phase transition, and it is found that the presence of the scalar field is instrumental in avoiding the initial singularity and gives freedom to the choice of initial conditions, giving advantage of studying different scenarios

Summary

Introduction

Though it is generally accepted that the Newtonian constant of gravity G plays the role of a coupling constant between geometry and matter in the Einstein field equations, it appears natural to look at this constant as a function of time in an evolving universe. [3] studied the homogeneous and isotropic cosmological model in which the parameter gamma of “Gammalaw” equation of state p = (γ–1) ρ varies continuously with cosmic time t. He studied the evolution of the universe as it goes from an inflationary phase to a radiationdominated phase. Its presence results in particle creation and thereby influence the subsequent evolution of the universe find Robertson-Walker models starting either from a non-singular origin with a minimum, non-zero G or from a singularity with a vanishing G, where G increases continuously in the radiation dominated era and approaches a constant value as the universe turns matter-dominated, the models approaching the standard model. Such study of the evolution of the universe will be of great importance in revealing the many mysteries of the different astrophysical objects in general and the universe in particular

Gp G 2

N 3 Rc2

Conclusions