Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Armchair graphene nanoribbons: PT-symmetry breaking and exceptional
  points without dissipation   We consider a single layer graphene nanoribbon with armchair edges in a
longitudinally constant external potential and point out that its transport
properties can be described by means of an effective non-Hermitian Hamiltonian.
We show that this system has some features typical of dissipative systems,
namely the presence of exceptional points and of PT-symmetry breaking, although
it is not dissipative.

29
The categories of this paper are: funct-an
19
The categories of this paper are: eess
34
The categories of this paper are: chem-ph
17
The categories of this paper are: q-fin
35
The categories of this paper are: mtrl-th
10
The categories of this paper are: q-bio
8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
26
The categories of this paper are: bayes-an
36
The categories of this paper are: cmp-lg
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph
24
The categories of this paper are: dg-ga
1
The categories of this paper are: cs
5
The categories of this paper are: gr-qc