Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Unconventional Cosmology   I review two cosmological paradigms which are alternative to the current
inflationary scenario. The first alternative is the "matter bounce", a
non-singular bouncing cosmology with a matter-dominated phase of contraction.
The second is an "emergent" scenario, which can be implemented in the context
of "string gas cosmology". I will compare these scenarios with the inflationary
one and demonstrate that all three lead to an approximately scale-invariant
spectrum of cosmological perturbations.

12
The categories of this paper are: nucl-th
22
The categories of this paper are: chao-dyn
23
The categories of this paper are: solv-int
17
The categories of this paper are: q-fin
26
The categories of this paper are: bayes-an
4
The categories of this paper are: cond-mat
3
The categories of this paper are: physics
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
28
The categories of this paper are: alg-geom
25
The categories of this paper are: patt-sol
9
The categories of this paper are: nlin
2
The categories of this paper are: math
19
The categories of this paper are: eess