Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An Alternative to Inflation   Inflationary models are generally credited with explaining the large scale
homogeneity, isotropy, and flatness of our universe as well as accounting for
the origin of structure (i.e., the deviations from exact homogeneity) in our
universe. We argue that the explanations provided by inflation for the
homogeneity, isotropy, and flatness of our universe are not satisfactory, and
that a proper explanation of these features will require a much deeper
understanding of the initial state of our universe. On the other hand,
inflationary models are spectacularly successful in providing an explanation of
the deviations from homogeneity. We point out here that the fundamental
mechanism responsible for providing deviations from homogeneity -- namely, the
evolutionary behavior of quantum modes with wavelength larger than the Hubble
radius -- will operate whether or not inflation itself occurs. However, if
inflation did not occur, one must directly confront the issue of the initial
state of modes whose wavelength was larger than the Hubble radius at the time
at which they were "born". Under some simple hypotheses concerning the "birth
time" and initial state of these modes (but without any "fine tuning"), it is
shown that non-inflationary fluid models in the extremely early universe would
result in the same density perturbation spectrum and amplitude as inflationary
models, although there would be no "slow roll" enhancement of the scalar modes.

28
The categories of this paper are: alg-geom
31
The categories of this paper are: ao-sci
26
The categories of this paper are: bayes-an
23
The categories of this paper are: solv-int
21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas
4
The categories of this paper are: cond-mat
19
The categories of this paper are: eess
9
The categories of this paper are: nlin
1
The categories of this paper are: cs
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The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
10
The categories of this paper are: q-bio
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The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex