Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Linear perturbations of an anisotropic Bianchi I model with a uniform
  magnetic field   In this work, we study the effect of a magnetic field on the growth of
cosmological perturbations. We develop a mathematical consistent treatment in
which a perfect fluid and a uniform magnetic field evolve together in a Bianchi
I universe. We then study the energy density perturbations on this background
with particular emphasis on the effect of the background magnetic field. We
develop a full relativistic solution which refines previous analysis in the
relativistic limit, recovers the known ones in the Newtonian treatment with
adiabatic sound speed, and it adds anisotropic effects to the relativistic ones
for perturbations with wavelength within the Hubble horizon. This represents a
refined approach on the perturbation theory of an isotropic universe in GR,
since most of the present studies deal with fully isotropic systems.

10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
0
The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
29
The categories of this paper are: funct-an
36
The categories of this paper are: cmp-lg
4
The categories of this paper are: cond-mat
21
The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
25
The categories of this paper are: patt-sol
22
The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph
17
The categories of this paper are: q-fin