Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Exact spherically-symmetric inhomogeneous model with n perfect fluids   We present the exact equations governing the dynamics of a
spherically-symmetric inhomogeneous model with n decoupled and non-comoving
perfect fluids. Thanks to the use of physically meaningful quantities we write
the set of 3+2n equations in a concise and transparent way. The n perfect
fluids can have general equations of state, thus making the model extremely
flexible to study a large variety of cosmological and astrophysical problems.
As applications we consider a model sourced by two non-comoving dust components
and a cosmological constant, and a model featuring dust and a dark energy
component with negligible speed of sound.

14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol
32
The categories of this paper are: atom-ph
29
The categories of this paper are: funct-an
2
The categories of this paper are: math
35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
36
The categories of this paper are: cmp-lg
28
The categories of this paper are: alg-geom
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The categories of this paper are: solv-int
10
The categories of this paper are: q-bio
3
The categories of this paper are: physics
20
The categories of this paper are: acc-phys
15
The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn