Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Defect formation in the early universe   Topological defects are common in many everyday systems. In general, they
appear if a symmetry is broken at a rapid phase transition. In this article, I
explain why it is believed that they should have also been formed in the early
universe and how that would have happened. If topological defects are found,
this will provide a way to study observationally the first fractions of a
second after the Big Bang, but their apparent absence can also tell us many
things about the early universe.

20
The categories of this paper are: acc-phys
19
The categories of this paper are: eess
23
The categories of this paper are: solv-int
26
The categories of this paper are: bayes-an
15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
31
The categories of this paper are: ao-sci
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th
13
The categories of this paper are: quant-ph
24
The categories of this paper are: dg-ga
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
8
The categories of this paper are: hep-ex