Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Pre-Big Bang Cosmology and Quantum Fluctuations   The quantum fluctuations of a homogeneous, isotropic, open pre-big bang model
are discussed. By solving exactly the equations for tensor and scalar
perturbations we find that particle production is negligible during the
perturbative Pre-Big Bang phase.

11
The categories of this paper are: hep-lat
32
The categories of this paper are: atom-ph
15
The categories of this paper are: nucl-ex
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an
10
The categories of this paper are: q-bio
26
The categories of this paper are: bayes-an
30
The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
3
The categories of this paper are: physics
36
The categories of this paper are: cmp-lg
23
The categories of this paper are: solv-int
37
The categories of this paper are: supr-con
0
The categories of this paper are: hep-ph