Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gravity and Domain Wall Problem   It is well known that the spontaneous breaking of discrete symmetries may
lead to conflict with big-bang cosmology. This is due to formation of domain
walls which give unacceptable contribution to the energy density of the
universe. On the other hand it is expected that gravity breaks global
symmetries explicitly. In this work we propose that this could provide a
natural solution to the domain-wall problem.

18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
2
The categories of this paper are: math
10
The categories of this paper are: q-bio
13
The categories of this paper are: quant-ph
25
The categories of this paper are: patt-sol
17
The categories of this paper are: q-fin
20
The categories of this paper are: acc-phys
27
The categories of this paper are: comp-gas
30
The categories of this paper are: q-alg
14
The categories of this paper are: math-ph
6
The categories of this paper are: astro-ph