Journal of Applied Physical Science International

Abstract

The distributions of radiation pressure and the total pressure of the universe were investigated in the general cosmic models in three time intervals. In the cosmic epoch t \(\le\) t_rm , logarithm of both radiation pressure and the total pressure descend gradually linearly with log (t). However, in the epoch t = t_{dec -} t_v , log(P_r(t)) decreases steeply up to t=6.2104 Myr, then it declines gradually until t=205.9406 Myr, hence it reduces slowly, whereas log(P(t)) decreases fast up to t=5.9406 Myr, afterwards it descends gradually until t = 112.8713 Myr, where it starts declining slowly. Nevertheless, in the time range t=t_v - 50 Gyr , log(P(t)) reduces fast up to t=1.4458 Gyr, then it descends in relatively less rate, while P(t) falls sharply until t=0.7229 Gyr, hence it declines rapidly up to t_app = 1.9277 Gyr, where P(t) approaches the dark energy pressure P_\(\Lambda\) . As P(t) decreases with cosmic time the horizon expansion speed of the universe d_h (t) descends continuously, while the negative values of the horizon expansion acceleration of the universe d_h (t) increase. On the other hand, the horizon volume speed of the universe expansion V_h (t) ascends with decreasing P(t) , whereas the horizon volume acceleration of the universe expansion V_h (t) descends. Slightly after t = t_app ,  V_h (t) increases to its maximum value at t=t_max, then it starts falling steeply with d_h (t) towards zero. However, at  t=t_max d_h (t) surges prominently towards zero, whereas V_h (t) fluctuates about this value. The drastic changes in d_h (t) , d_h (t) , V_h (t) and V_h (t) following the outstanding decrease in P(t) at t=t_app exhibits strong dependence of the cosmic dynamics on the total pressure of the universe.