Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Matter-positronium interaction: An exact diagonalization study of the He
  atom - positronium system
1
The categories of this paper are: cs
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
17
The categories of this paper are: q-fin
20
The categories of this paper are: acc-phys
2
The categories of this paper are: math
27
The categories of this paper are: comp-gas
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
0
The categories of this paper are: hep-ph
10
The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
13
The categories of this paper are: quant-ph
33
The categories of this paper are: plasm-ph
36
The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc