Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Universality and backreaction in a general-relativistic accretion of
  steady fluids   The spherically symmetric steady accretion of polytropic perfect fluids onto
a black hole is the simplest flow model that can demonstrate the effects of
backreaction. The analytic and numerical investigation reveals that
backreaction keeps intact most of the characteristics of the sonic point. For
any such system, with the only free parameter being the relative abundance of
the fluid, the mass accretion rate achieves maximal value when the mass of the
fluid is universally 1/3 of the total mass.

19
The categories of this paper are: eess
10
The categories of this paper are: q-bio
29
The categories of this paper are: funct-an
17
The categories of this paper are: q-fin
7
The categories of this paper are: hep-th
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
11
The categories of this paper are: hep-lat
4
The categories of this paper are: cond-mat
28
The categories of this paper are: alg-geom
23
The categories of this paper are: solv-int
26
The categories of this paper are: bayes-an
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys