Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dirac electron in a Coulomb Field in 2+1 Dimensions   Exact solutions of Dirac equation in two spatial dimensions in the Coulomb
field are obtained. Equation which determines the so-called critical charge of
the Coulomb field is derived and solved for a simple model.

26
The categories of this paper are: bayes-an
15
The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn
31
The categories of this paper are: ao-sci
2
The categories of this paper are: math
21
The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom
18
The categories of this paper are: econ
11
The categories of this paper are: hep-lat
34
The categories of this paper are: chem-ph
17
The categories of this paper are: q-fin
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
8
The categories of this paper are: hep-ex