Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Effective interaction potential and superfluid-solid transition of
  spatially indirect excitons
14
The categories of this paper are: math-ph
11
The categories of this paper are: hep-lat
16
The categories of this paper are: stat
23
The categories of this paper are: solv-int
2
The categories of this paper are: math
18
The categories of this paper are: econ
34
The categories of this paper are: chem-ph
35
The categories of this paper are: mtrl-th
10
The categories of this paper are: q-bio
20
The categories of this paper are: acc-phys
1
The categories of this paper are: cs
3
The categories of this paper are: physics
30
The categories of this paper are: q-alg
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin