Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Explanation for the isotropy of the Dirac cone in graphene   It is shown that in the absence of spontaneous symmetry breaking the Dirac
cones in the system of interacting electrons on honeycomb lattice are isotropic
at low energies. The effect is due to the $Z_3$ subgroup of the $D_3$ symmetry
group of the dispersion relation of Dirac quasiparticles. Consequences of the
violations of the $Z_3$ or the sublattice symmetry are discussed.

36
The categories of this paper are: cmp-lg
21
The categories of this paper are: adap-org
22
The categories of this paper are: chao-dyn
25
The categories of this paper are: patt-sol
17
The categories of this paper are: q-fin
15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci
6
The categories of this paper are: astro-ph
30
The categories of this paper are: q-alg
23
The categories of this paper are: solv-int
37
The categories of this paper are: supr-con
0
The categories of this paper are: hep-ph
12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th