Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A note on the three dimensional Dirac operator with zigzag type boundary
  conditions   In this note the three dimensional Dirac operator $A_m$ with boundary
conditions, which are the analogue of the two dimensional zigzag boundary
conditions, is investigated. It is shown that $A_m$ is self-adjoint in
$L^2(\Omega;\mathbb{C}^4)$ for any open set $\Omega \subset \mathbb{R}^3$ and
its spectrum is described explicitly in terms of the spectrum of the Dirichlet
Laplacian in $\Omega$. In particular, whenever the spectrum of the Dirichlet
Laplacian is purely discrete, then also the spectrum of $A_m$ consists of
discrete eigenvalues that accumulate at $\pm \infty$ and one additional
eigenvalue of infinite multiplicity.

13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
22
The categories of this paper are: chao-dyn
26
The categories of this paper are: bayes-an
1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci
30
The categories of this paper are: q-alg
28
The categories of this paper are: alg-geom
21
The categories of this paper are: adap-org
11
The categories of this paper are: hep-lat