Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Need the masses of unstable particles and their antiparticles be equal
  in the CPT--invariant system?
12
The categories of this paper are: nucl-th
2
The categories of this paper are: math
11
The categories of this paper are: hep-lat
3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
29
The categories of this paper are: funct-an
15
The categories of this paper are: nucl-ex
14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
35
The categories of this paper are: mtrl-th
33
The categories of this paper are: plasm-ph
24
The categories of this paper are: dg-ga
25
The categories of this paper are: patt-sol
20
The categories of this paper are: acc-phys
26
The categories of this paper are: bayes-an