Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Conformal Symmetry and Cosmological Entropy Production   Introducing an effective refraction index of an isotropic cosmic medium, we
investigate the cosmological fluid dynamics which is consistent with a
conformal, timelike symmetry of a corresponding ``optical'' metric. We
demonstrate that this kind of symmetry is compatible with the existence of a
negative viscous pressure and, consequently, with cosmological entropy
production. We establish an exactly solvable model according to which the
viscous pressure is a consequence of a self-interacting one-particle force
which is self-consistently exerted on the microscopic particles of a
relativistic gas. Furthermore, we show that a sufficiently high decay rate of
the refraction index of an ultrarelativistic cosmic medium results in an
inflationary expansion of the universe.

19
The categories of this paper are: eess
14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol
18
The categories of this paper are: econ
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
29
The categories of this paper are: funct-an
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The categories of this paper are: solv-int
4
The categories of this paper are: cond-mat
32
The categories of this paper are: atom-ph
15
The categories of this paper are: nucl-ex
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The categories of this paper are: q-fin
12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th