Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Effects of the Shear Viscosity on the Character of Cosmological
  Evolution   Bianchi type I cosmological models are studied that contain a stiff fluid
with a shear viscosity that is a power function of the energy density, such as
$\zeta = \alpha \epsilon^n$. These models are analyzed by describing the
cosmological evolutions as the trajectories in the phase plane of Hubble
functions. The simple and exact equations that determine these flows are
obtained when $n$ is an integer. In particular, it is proved that there is no
Einstein initial singularity in the models of $0\leq n < 1$. Cosmologies are
found to begin with zero energy density and in the course of evolution the
gravitational field will create matter. At the final stage, cosmologies are
driven to the isotropic Fnedmann universe. It is also pointed out that although
the anisotropy will always be smoothed out asymptotically, there are solutions
that simultaneously possess non-positive and non-negative Hubble functions for
all time. This means that the cosmological dimensional reduction can work even
if the matter fluid having shear viscosity. These characteristics can also be
found in any-dimensional models.

13
The categories of this paper are: quant-ph
31
The categories of this paper are: ao-sci
12
The categories of this paper are: nucl-th
21
The categories of this paper are: adap-org
29
The categories of this paper are: funct-an
33
The categories of this paper are: plasm-ph
24
The categories of this paper are: dg-ga
4
The categories of this paper are: cond-mat
35
The categories of this paper are: mtrl-th
22
The categories of this paper are: chao-dyn
9
The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
25
The categories of this paper are: patt-sol
0
The categories of this paper are: hep-ph
30
The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex