Mild Inflation and Modified General Relativity in the Early Universe

Abstract

This article deals with particle creation andthe production of specific entropy per baryon in theearly universe, which is regarded as a thermodynamicallyopen system in the sense of Prigogine. The modified general relativity (MGR) theory of Rastall,Al-Rawaf, and Taha is employed. It contains an extraindependent constant η which is peculiar to thenon-Newtonian regime, besides the usual gravitationalconstant. Usual general relativity (GR) appears here asa special case for η = 1. With a modifiedthermodynamic energy conservation law, it is possible toobtain an equation for the expansion scalar byincorporating the epoch dependence of elementary particlemasses. The epoch dependence of particle masses for theRobertson-Walker (RW) universe appears as a consequenceof hadronic matter extension in a microlocal space-time regarded as anisotropic and Finslerian. Thegoverning equations in the present formalism specify theequation of state and give a solution for the expansionscalar. This solution represents a mild inflationary phase in the very early universe. It is alsoshown that there are no 'turn-on' and'turn-off' problems for this mild inflation.It can account for particle creation and production ofspecific entropy per baryon consistent with the observation. Theproduction of specific entropy per baryon is alsoconsidered here in the MGR framework with theintroduction of viscous pressure; the calculated valueis in good agreement with observation for the GR case, butfor the MGR case, in order to have its value withinobservational limits, η must lie in the range 0.75≤ η ≤ 1. It is also argued that this formalismdoes not have horizon and flatnessproblems.