Bulk viscosity,Kaluza-Klein models and inflation

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 Kaluza-Klein cosmological model withd noncompact andD compact space-like dimensions, in particular we considerD=1, the second one is to use an energy-momentum 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 non-relativistic 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 non-compact 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 non-compact 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 non-compact 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 higher-dimensional matter is one in which the kinetic approach is valid, the effective tensor in the non-compact space-time has the property that this treatment is not applicable.Supported in part by CONACYT grant P228CCOX891723, and DGICSA SEP grant C90-03-03447.