Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: From polytropic to barotropic perfect fluids in general-relativistic
  hydrodynamics   Two general-relativistic hydrodynamical models are considered: a model of
self-gravitating static configurations of perfect fluid and a model of steady
accretion of fluid onto a black hole. We generalise analytic results obtained
for the original polytropic versions of these models onto a wider class of
barotropic equations of state. The knowledge about the polytropic solutions is
used to establish bounds on certain characteristic quantities appearing in both
cases.

8
The categories of this paper are: hep-ex
9
The categories of this paper are: nlin
17
The categories of this paper are: q-fin
21
The categories of this paper are: adap-org
1
The categories of this paper are: cs
31
The categories of this paper are: ao-sci
14
The categories of this paper are: math-ph
6
The categories of this paper are: astro-ph
33
The categories of this paper are: plasm-ph
28
The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
19
The categories of this paper are: eess
7
The categories of this paper are: hep-th
2
The categories of this paper are: math
16
The categories of this paper are: stat
10
The categories of this paper are: q-bio