Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Back Reaction Problem in the Inflationary Universe   We investigate the back reaction of cosmological perturbations on an
inflationary universe using the renormalization-group method. The second-order
zero mode solution which appears by the nonlinearity of the Einstein equation
is regarded as a secular term of a perturbative expansion, we renormalized a
constant of integration contained in the background solution and absorbed the
secular term to this constant in a gauge-invariant manner. The resultant
renormalization-group equation describes the back reaction effect of
inhomogeneity on the background universe. For scalar type classical
perturbation, by solving the renormalization-group equation, we find that the
back reaction of the long wavelength fluctuation works as a positive spatial
curvature, and the short wavelength fluctuation works as a radiation fluid. For
the long wavelength quantum fluctuation, the effect of back reaction is
equivalent to a negative spatial curvature.

30
The categories of this paper are: q-alg
9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph
25
The categories of this paper are: patt-sol
33
The categories of this paper are: plasm-ph
21
The categories of this paper are: adap-org
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The categories of this paper are: comp-gas
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
2
The categories of this paper are: math
26
The categories of this paper are: bayes-an
34
The categories of this paper are: chem-ph
3
The categories of this paper are: physics
7
The categories of this paper are: hep-th
14
The categories of this paper are: math-ph
4
The categories of this paper are: cond-mat