Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Shear viscosity, relaxation and collision times in spherically symmetric
  spacetimes   We interpret as shear viscosity the anisotropic pressure that emerges in
inhomogeneous spherically symmetric spacetimes described by the
Lemaitre-Tolman-Bondi (LTB) metric in a comoving frame. By assuming that local
isotropic pressure and energy density satisfy a generic ideal gas equation of
state, we reduce the field equations to a set of evolution equations based on
auxiliary quasi-local variables. We examine the transport equation of shear
viscosity from Extended Irreversible Thermodynamics and use a numerical
solution of the evolution equations to obtain the relaxation times for the full
and "truncated" versions. Considering a gas of cold dark matter WIMPS after its
decoupling from the cosmic fluid, we show that the relaxation times for the
general equation are qualitatively analogous to collision times, while the
truncated version is inadequate to describe transient phenomena of transition
to equilibrium.

13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
21
The categories of this paper are: adap-org
0
The categories of this paper are: hep-ph
36
The categories of this paper are: cmp-lg
28
The categories of this paper are: alg-geom
6
The categories of this paper are: astro-ph
35
The categories of this paper are: mtrl-th
17
The categories of this paper are: q-fin
25
The categories of this paper are: patt-sol
12
The categories of this paper are: nucl-th
22
The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio
32
The categories of this paper are: atom-ph
26
The categories of this paper are: bayes-an