Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Derivation of the paraxial form of the angular momentum of the
  electromagnetic field from the general form   It is shown how the standard forms for the spin and orbital components of the
angular momentum of a paraxial wave of electromagnetic radiation are obtained
from the general expressions for the angular momentum that have been derived
recently. This result will enable the general expressions for angular momentum
to be applied with confidence to the many configurations of electromagnetic
fields that are more complicated than plane or paraxial waves.

11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
24
The categories of this paper are: dg-ga
15
The categories of this paper are: nucl-ex
27
The categories of this paper are: comp-gas
36
The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn
32
The categories of this paper are: atom-ph
33
The categories of this paper are: plasm-ph
9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
5
The categories of this paper are: gr-qc
16
The categories of this paper are: stat
10
The categories of this paper are: q-bio