Rip/singularity free cosmology models with bulk viscosity

Exact Solutions in Multidimensional Cosmology with Shear and Bulk Viscosity

Multidimensional cosmological model describing the evolution of a fluid with shear and bulk viscosity in n Ricci-flat spaces is investigated. The barotropic equation of state for the density and the pressure in each space is assumed. The second equation of state is chosen in the form when the bulk and the shear viscosity coefficients are inversely proportional to the volume of the Universe. The...

Universe models with negative bulk viscosity

The concept of negative temperatures has occasionally been used in connection with quantum systems. A recent example of this sort is reported in the paper of S. Braun et al. [Science 339, 52 (2013)], where an attractively interacting ensemble of ultracold atoms is investigated experimentally and found to correspond to a negative-temperature system since the entropy decreases with increasing ene...

Entropy generation in a five-dimensional cosmology admitting bulk viscosity

Cosmology with bulk pressure

It is well known that cosmological particle production processes may phenomenologically be described in terms of effective viscous pressures. We investigate the consistency of this approach on the level of relativistic kinetic theory, using a Boltzmann equation with an additional source term that leads to a change in the number of gas particles. For a simple creation rate model we find the cond...

Bulk viscosity in quasi particle models

We discuss transport properties of dynamical fluid composed of quasi-particles whose masses depend on temperature and charge chemical potentials. Based on the relativistic kinetic theory formulated under the relaxation time approximation, we derive a general expression for the bulk viscosity in the quasi-particle medium. We show that dynamically generated particle masses imply an essential modi...