Akademik Veri Yönetim Sistemi
GRAVITATION & COSMOLOGY, cilt.25, ss.397-406, 2019 (SCI-Expanded)
Using variable gravitational and cosmological constants, the mechanism of particle creation in the universe is studied for Friedmann-Robertson-Walker (FRW) space-times at high dimensions to explain the early deceleration and present accelerating phases. To investigate the dynamics of these phases, we consider two scale factor of the forms a(t) = root t(alpha)e(t) and a(t) = (m)root sin h(kt), which yield two different time-dependent deceleration parameters. Firstly, we modify the d-dimensional time-dependent field equations, including the general formulation of particle creation and entropy generation mechanisms. Then, we investigate the time dependence of a few quantities such as the particle creation rate psi, the entropy S, the gravitational constant G, the cosmological constant Lambda, the energy density rho, the deceleration parameter q, etc. We show that all constants and quantities, except the gravitational constant G and the entropy S, characteristically decrease with time for two kinds of scale factors in all dimensions. However, the gravitational constant G and the entropy S increase with time. Additionally, we show that the cosmological constant Lambda is unexpectedly independent of the particle creation mechanism, unlike G.