Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Entropy of a Classical Stochastic Field and Cosmological Perturbation   We propose a general definition of nonequilibrium entropy of a classical
stochastic field. As an example of particular interest in cosmology we apply
this definition to compute the entropy of density perturbations in an
inflationary Universe. On the scales of structures in the Universe, the entropy
of density perturbations dominates over the statistical fluctuations of the
entropy of cosmic microwave photons, indicating the relevance of the entropy of
density fluctuations for structure formation.

3
The categories of this paper are: physics
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
27
The categories of this paper are: comp-gas
34
The categories of this paper are: chem-ph
26
The categories of this paper are: bayes-an
10
The categories of this paper are: q-bio
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The categories of this paper are: cond-mat
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The categories of this paper are: cs
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The categories of this paper are: math
15
The categories of this paper are: nucl-ex
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The categories of this paper are: nucl-th
14
The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph