Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gravitational Instability in Presence of Bulk Viscosity: the Jeans Mass
  and the Quasi-Isotropic Solution   This paper focuses on the analysis of the gravitational instability in
presence of bulk viscosity both in Newtonian regime and in the
fully-relativistic approach. The standard Jeans Mechanism and the
Quasi-Isotropic Solution are treated expressing the bulk-viscosity coefficient
$\zeta$ as a power-law of the fluid energy density $\rho$, i.e.,
$\zeta=\zo\rho^{s}$. In the Newtonian regime, the perturbation evolution is
founded to be damped by viscosity and the top-down mechanism of structure
fragmentation is suppressed. The value of the Jeans Mass remains unchanged also
in presence of viscosity. In the relativistic approach, we get a power-law
solution existing only in correspondence to a restricted domain of $\zo$.

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The categories of this paper are: nlin
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The categories of this paper are: chao-dyn
33
The categories of this paper are: plasm-ph
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
28
The categories of this paper are: alg-geom
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
30
The categories of this paper are: q-alg
32
The categories of this paper are: atom-ph
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
6
The categories of this paper are: astro-ph