Time Dependence of Various Cosmological Parameters in the Framework of Kaluza-Klein Space-Time

Abstract

A theoretical model, regarding the time dependence of several cosmological parameters, has been constructed in the present study, in the framework of Kaluza-Klein theory, using its field equations for a spatially flat metric. Time dependent empirical expressions of the cosmological constant and the equation of state (EoS) parameter have been substituted into the field equations to determine the time dependence of various cosmological parameters. Time variations of these parameters have been shown graphically. The cosmological features obtained from this model are found to be in agreement with the observed characteristics of the accelerating universe. Interestingly, the signature flipping of the deceleration parameter, from positive to negative, is predicted by this model, indicating a transformation of the universe from a state of decelerated expansion to accelerated expansion, as obtained from astrophysical observations. Time dependence of the gravitational constant (G), energy density (?), cosmological constant (?) and the EoS parameter (?) have been determined and depicted graphically in the present study.

Variation of Scale Factor and Deceleration Parameter Through the Cosmic Evolution of Time and Temperature

“…The deceleration parameter variation with time, temperature and the scale factor Figs. (3-5) show a change of sign from positive (1 and 0.5 respectively at radiation and matter dominated eras) to negative value (-0.27 now and -0.33 later on) indicating a transition from a phase of decelerated expansion at both radiation and matter dominated eras to accelerated expansion now and time beyond, (Bengochea, 2019;Roy et al, 2019;Lin and Qian, 2020).…”