Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Equivalence of two mathematical forms for the bound angular momentum of
  the electromagnetic field   It is shown that the mathematical form, obtained in a recent paper, for the
angular momentum of the electromagnetic field in the vicinity of electric
charge is equivalent to another form obtained previously by Cohen-Tannoudji,
Dupont-Roc and Gilbert. In this version of the paper an improved derivation is
given.

34
The categories of this paper are: chem-ph
17
The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph
24
The categories of this paper are: dg-ga
32
The categories of this paper are: atom-ph
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
8
The categories of this paper are: hep-ex
14
The categories of this paper are: math-ph
18
The categories of this paper are: econ
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
13
The categories of this paper are: quant-ph
31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th