Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Self-energy O(alpha^2) correction to the positronium decay rate
3
The categories of this paper are: physics
22
The categories of this paper are: chao-dyn
4
The categories of this paper are: cond-mat
23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess
15
The categories of this paper are: nucl-ex
14
The categories of this paper are: math-ph
13
The categories of this paper are: quant-ph
1
The categories of this paper are: cs
2
The categories of this paper are: math
9
The categories of this paper are: nlin
18
The categories of this paper are: econ
6
The categories of this paper are: astro-ph
25
The categories of this paper are: patt-sol