Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Qualitative analysis of trapped Dirac fermions in graphene   We study the confinement of Dirac fermions in graphene and in carbon
nanotubes by an external magnetic field, mechanical deformations or
inhomogeneities in the substrate. By applying variational principles to the
square of the Dirac operator, we obtain sufficient and necessary conditions for
confinement of the quasi-particles. The rigorous theoretical results are
illustrated on the realistic examples of the three classes of traps.

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
29
The categories of this paper are: funct-an
18
The categories of this paper are: econ
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
8
The categories of this paper are: hep-ex
25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
17
The categories of this paper are: q-fin
3
The categories of this paper are: physics
31
The categories of this paper are: ao-sci
28
The categories of this paper are: alg-geom