Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the Spectrum of Fluctuations in an Effective Field Theory of the
  Ekpyrotic Universe   We consider the four-dimensional effective field theory which has been used
in previous studies of perturbations in the Ekpyrotic Universe, and discuss the
spectrum of cosmological fluctuations induced on large scales by quantum
fluctuations of the bulk brane. By matching cosmological fluctuations on a
constant energy density hypersurface we show that the growing mode during the
very slow collapsing pre-impact phase couples only to the decaying mode in the
expanding post-impact phase, and that hence no scale-invariant spectrum of
adiabatic fluctuations is generated. Note that our conclusions may not apply to
improved toy models for the Ekpyrotic scenario.

16
The categories of this paper are: stat
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ
10
The categories of this paper are: q-bio
24
The categories of this paper are: dg-ga
2
The categories of this paper are: math
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The categories of this paper are: math-ph
4
The categories of this paper are: cond-mat
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The categories of this paper are: eess
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-fin
3
The categories of this paper are: physics
29
The categories of this paper are: funct-an
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The categories of this paper are: acc-phys
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The categories of this paper are: plasm-ph
1
The categories of this paper are: cs