Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Neutrinos and electrons in background matter   We present a rather powerful method in investigations of different phenomena
that can appear when neutrinos and electrons propagate in background matter.
This method is based on the use of the modified Dirac equations for particles
wave functions, in which the correspondent effective potentials accounting for
the matter influence on particles are included.

31
The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
8
The categories of this paper are: hep-ex
22
The categories of this paper are: chao-dyn
24
The categories of this paper are: dg-ga
28
The categories of this paper are: alg-geom
9
The categories of this paper are: nlin
37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess
2
The categories of this paper are: math
11
The categories of this paper are: hep-lat
21
The categories of this paper are: adap-org
30
The categories of this paper are: q-alg
14
The categories of this paper are: math-ph
4
The categories of this paper are: cond-mat