Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A classical, non-singular, bouncing universe   We present a model for a classical, non-singular bouncing cosmology without
violation of the null energy condition (NEC). The field content is General
Relativity plus a real scalar field with a canonical kinetic term and only
renormalizable, polynomial type self-interaction for the scalar field in the
Jordan frame. The universe begins vacuum-energy dominated and is contracting at
$t=-\infty$. We consider a closed universe with a positive spatial curvature,
which is responsible for the universe bouncing without any NEC violation. An
$R\phi^2$ coupling between the Ricci scalar and the scalar field drives the
scalar from the initial false vacuum to the true vacuum during the bounce. The
model is sub-Planckian throughout its evolution and every dimensionful
parameter is below the effective field theory scale $M_P$, so we expect no
ghost-type or tachyonic instabilities. This model solves the horizon problem
and extends co-moving particle geodesics to past infinity, resulting in a
geodesically complete universe without singularities. We solve the Friedman
equations and the scalar field equation of motion numerically, and analytically
under certain approximations.

32
The categories of this paper are: atom-ph
24
The categories of this paper are: dg-ga
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
12
The categories of this paper are: nucl-th
25
The categories of this paper are: patt-sol
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
16
The categories of this paper are: stat
2
The categories of this paper are: math
33
The categories of this paper are: plasm-ph
28
The categories of this paper are: alg-geom
14
The categories of this paper are: math-ph
26
The categories of this paper are: bayes-an
27
The categories of this paper are: comp-gas