Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Accidental degeneracy and topological phase transitions in
  two-dimensional core-shell dielectric photonic crystals   A simple core-shell two-dimensional photonic crystal is studied where the
triangle lattice symmetry and $C_{6v}$ rotation symmetry leads to rich physics
in the study of accidental degeneracy's in photonic bands. We systematically
evaluate different types of accidental nodal points, depending on the
dispersions around them and their topological properties, when the geometry and
permittivity are continuously changed. These accidental nodal points can be the
critical states lying between a topological phase and a normal phase and are
thus important for the study of topological photonic states. In time-reversal
systems, this leads to the photonic quantum spin Hall insulator where the spin
is defined upon the orbital angular momentum for transverse-magnetic
polarization. We study the topological phase transition as well as the
properties of the edge and bulk states and their application potentials in
optics.

36
The categories of this paper are: cmp-lg
18
The categories of this paper are: econ
34
The categories of this paper are: chem-ph
19
The categories of this paper are: eess
26
The categories of this paper are: bayes-an
2
The categories of this paper are: math
14
The categories of this paper are: math-ph
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
7
The categories of this paper are: hep-th
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs
23
The categories of this paper are: solv-int
12
The categories of this paper are: nucl-th
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci