Bulk viscosity, KaluzaKlein models and inflation
Abstract
In this work we have employed two hypotheses which have been separately used in order to try to solve the horizon problem, the first one is to take a KaluzaKlein cosmological model withd noncompact andD compact spacelike dimensions, in particular we considerD=1, the second one is to use an energymomentum tensor depicting a fluid out of equilibrium, in particular we take a mixture of two gases, one is formed by relativistic particles and the other one is a gas constituted by nonrelativistic particles and they are not in thermodynamical equilibrium, such that a bulk viscosity term arises. Without actually solving the Einstein equations, we prove that the scale factor of the noncompact space is a monotonic increasing function of time, and that if the scale factor of the compact space reaches a maximum at a certain time then the noncompact space is driven to expand rapidly, and, therefore, hinting us about the possibility of solving the horizon problem. The effective pressure and density in the noncompact space are found and it is proved that they satisfy the condition for having generalized inflation, and, therefore, might permit to solve the horizon problem, even in the case ofD=1, there is no need of a large number of extra dimensions, as some other previous authors have found. Despite our higherdimensional matter is one in which the kinetic approach is valid, the effective tensor in the noncompact spacetime has the property that this treatment is not applicable.
 Publication:

Astrophysics and Space Science
 Pub Date:
 November 1992
 DOI:
 10.1007/BF00645735
 Bibcode:
 1992Ap&SS.197..225C
 Keywords:

 Astronomical Models;
 Cosmology;
 Field Theory (Physics);
 SpaceTime Functions;
 Energy Transfer;
 Universe;
 Viscosity;
 Astrophysics