Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: A formal framework for the study of the notion of undefined particle
  number in quantum mechanics
31
The categories of this paper are: ao-sci
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
19
The categories of this paper are: eess
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
8
The categories of this paper are: hep-ex
32
The categories of this paper are: atom-ph
17
The categories of this paper are: q-fin
35
The categories of this paper are: mtrl-th
12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
6
The categories of this paper are: astro-ph
11
The categories of this paper are: hep-lat