Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Preheating in Generalized Einstein Theories   We study the preheating scenario in Generalized Einstein Theories,
considering a class of such theories which are conformally equivalent to those
of an extra field with a modified potential in the Einstein frame. Resonant
creation of bosons from oscillating inflaton has been studied before in the
context of general relativity taking also into account the effect of metric
perturbations in linearized gravity. As a natural generalization we include the
dilatonic/Brans-Dicke field without any potential of its own and in particular
we study the linear theory of perturbations including the metric perturbations
in the longitudinal gauge. We show that there is an amplification of the
perturbations in the dilaton/Brans-Dicke field on super-horizon scales (k -> 0)
due to the fluctuations in metric, thus leading to an oscillating Newton's
constant with very high frequency within the horizon and with growing amplitude
outside the horizon. We briefly mention the entropy perturbations generated by
such fluctuations and also mention that there is a possibility to excite the
Kaluza-Klein modes in the theories where the dilatonic/Brans-Dicke field is
interpreted as a homogeneous field appearing due to the dimensional reduction
from the higher dimensional theories.

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The categories of this paper are: hep-th
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The categories of this paper are: math
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The categories of this paper are: supr-con
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The categories of this paper are: econ
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The categories of this paper are: q-fin
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The categories of this paper are: hep-lat
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The categories of this paper are: chao-dyn
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The categories of this paper are: atom-ph
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The categories of this paper are: cs
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The categories of this paper are: stat
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The categories of this paper are: quant-ph
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The categories of this paper are: physics
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The categories of this paper are: nucl-ex
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The categories of this paper are: funct-an
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The categories of this paper are: alg-geom
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The categories of this paper are: cmp-lg