Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Alternative Discrete Energy Solutions to the Free Particle Dirac
  Equation   The usual method of solving the free particle Dirac equation results in the
so called continuum energy solutions. Here, we take a different approach and
find a set of solutions with quantized energies which are proportional to the
total angular momentum.

13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
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The categories of this paper are: eess
24
The categories of this paper are: dg-ga
36
The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc
30
The categories of this paper are: q-alg
2
The categories of this paper are: math
16
The categories of this paper are: stat
4
The categories of this paper are: cond-mat
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs
8
The categories of this paper are: hep-ex
0
The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
21
The categories of this paper are: adap-org