Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Rare decays of the positronium ion and molecule, $\text{Ps}^{-}\to
  e^{-}\gamma$ and $\text{Ps}_{2}\to
  e^{+}e^{-}\gamma,~\gamma\gamma,~e^{+}e^{-}$
14
The categories of this paper are: math-ph
9
The categories of this paper are: nlin
13
The categories of this paper are: quant-ph
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ
5
The categories of this paper are: gr-qc
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
28
The categories of this paper are: alg-geom
4
The categories of this paper are: cond-mat
25
The categories of this paper are: patt-sol
17
The categories of this paper are: q-fin
1
The categories of this paper are: cs
23
The categories of this paper are: solv-int
21
The categories of this paper are: adap-org
20
The categories of this paper are: acc-phys