Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On quantization of electromagnetic field   These are six papers joined by the same title. The main topics are:
  1. algebraic nature of quantization of relativistic fields,
  2. constructive definition of space of states of quantum electromagnetic
field,
  3. structure of space of states of quantum electromagnetic field from
functional analysis standpoint.

3
The categories of this paper are: physics
25
The categories of this paper are: patt-sol
8
The categories of this paper are: hep-ex
34
The categories of this paper are: chem-ph
10
The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
5
The categories of this paper are: gr-qc
27
The categories of this paper are: comp-gas
29
The categories of this paper are: funct-an
37
The categories of this paper are: supr-con
11
The categories of this paper are: hep-lat
26
The categories of this paper are: bayes-an
13
The categories of this paper are: quant-ph
35
The categories of this paper are: mtrl-th
15
The categories of this paper are: nucl-ex