Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Non-Equilibrium Evolution of Scalar Fields in FRW Cosmologies I   We derive the effective equations for the out of equilibrium time evolution
of the order parameter and the fluctuations of a scalar field theory in
spatially flat FRW cosmologies.The calculation is performed both to one-loop
and in a non-perturbative, self-consistent Hartree approximation.The method
consists of evolving an initial functional thermal density matrix in time and
is suitable for studying phase transitions out of equilibrium. The
renormalization aspects are studied in detail and we find that the counterterms
depend on the initial state. We investigate the high temperature expansion and
show that it breaks down at long times. We also obtain the time evolution of
the initial Boltzmann distribution functions, and argue that to one-loop order
or in the Hartree approximation, the time evolved state is a ``squeezed''
state. We illustrate the departure from thermal equilibrium by numerically
studying the case of a free massive scalar field in de Sitter and radiation
dominated cosmologies. It is found that a suitably defined non-equilibrium
entropy per mode increases linearly with comoving time in a de Sitter
cosmology, whereas it is {\it not} a monotonically increasing function in the
radiation dominated case.

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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: econ
34
The categories of this paper are: chem-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: stat
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The categories of this paper are: adap-org
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The categories of this paper are: nlin
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The categories of this paper are: patt-sol
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The categories of this paper are: plasm-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: math
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-bio
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The categories of this paper are: math-ph