Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Stimulated Raman and Brillouin backscattering of collimated beams
  carrying orbital angular momentum   We study theoretically the exchange of angular momentum between
electromagnetic and electrostatic waves in a plasma, due to the stimulated
Raman and Brillouin backscattering processes. Angular momentum states for
plasmon and phonon fields are introduced for the first time. We demonstrate
that these states can be excited by nonlinear wave mixing, associated with the
scattering processes. This could be relevant for plasma diagnostics, both in
laboratory and in space. Nonlinearly coupled paraxial equations and instability
growth rates are derived.

21
The categories of this paper are: adap-org
23
The categories of this paper are: solv-int
28
The categories of this paper are: alg-geom
35
The categories of this paper are: mtrl-th
10
The categories of this paper are: q-bio
5
The categories of this paper are: gr-qc
14
The categories of this paper are: math-ph
36
The categories of this paper are: cmp-lg
8
The categories of this paper are: hep-ex
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The categories of this paper are: q-fin
16
The categories of this paper are: stat
33
The categories of this paper are: plasm-ph
24
The categories of this paper are: dg-ga
29
The categories of this paper are: funct-an
0
The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas