Cosmological entropy production and viscous processes in the (1+3+6)-dimensional space-times

TL;DR

This paper investigates entropy production in a (1+3+6)-dimensional cosmological model, focusing on viscous processes and their role in entropy growth and space decoupling during early universe evolution.

Contribution

It introduces a detailed analysis of viscous entropy production in higher-dimensional cosmology, highlighting conditions for critical entropy levels and space decoupling.

Findings

Viscous dissipation enhances entropy production in the 3D outer space.

Conditions for reaching Guth-level entropy and space decoupling are identified.

Total entropy in 9D space is related to entropy in 3D space during early expansion.

Abstract

The cosmological entropy production is studied in the (1+3+6)-dimensional space-times consisting of the outer space (the 3-dimensional expanding section) and the inner space (the 6-dimensional section). The inner space expands initially and contracts later. First it is shown how the production of the 3-dimensional entropy S_3 within the horizon is strengthened by the dissipation due to viscous processes between the two spaces, in which we consider the viscosity caused by the gravitational-wave transport. Next it is shown under what conditions we can have the critical epoch when S_3 reaches the value 10^{88} in the Guth level and at the same time the outer space is decoupled from the inner space. Moreover, the total entropy S_9 in the 9-dimensional space at the primeval expanding stage is also shown corresponding to S_3.