Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Berezinskii-Kosterlitz-Thouless-type transitions in d=2 quantum O(2) and
  O(2)xO(2) nonlinear sigma models
6
The categories of this paper are: astro-ph
17
The categories of this paper are: q-fin
37
The categories of this paper are: supr-con
24
The categories of this paper are: dg-ga
5
The categories of this paper are: gr-qc
3
The categories of this paper are: physics
12
The categories of this paper are: nucl-th
11
The categories of this paper are: hep-lat
30
The categories of this paper are: q-alg
13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
32
The categories of this paper are: atom-ph
20
The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
31
The categories of this paper are: ao-sci
14
The categories of this paper are: math-ph