Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Photonic analog of graphene model and its extension -- Dirac cone,
  symmetry, and edge states --   This paper presents a theoretical analysis on bulk and edge states in
honeycomb lattice photonic crystals with and without time-reversal and/or
space-inversion symmetries. Multiple Dirac cones are found in the photonic band
structure and the mass gaps are controllable via symmetry breaking. The zigzag
and armchair edges of the photonic crystals can support novel edge states that
reflect the symmetries of the photonic crystals. The dispersion relation and
the field configuration of the edge states are analyzed in detail in comparison
to electronic edge states. Leakage of the edge states to free space is inherent
in photonic systems and is fully taken into account in the analysis. A
topological relation between bulk and edge, which is analogous to that found in
quantum Hall systems, is also verified.

18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
12
The categories of this paper are: nucl-th
13
The categories of this paper are: quant-ph
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
22
The categories of this paper are: chao-dyn
16
The categories of this paper are: stat
24
The categories of this paper are: dg-ga
28
The categories of this paper are: alg-geom
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol