Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Accidental and symmetry-protected bound states in the continuum in
  planar photonic-crystal structures, studied by the resonant-state expansion   The resonant-state expansion (RSE) provides a precise and computationally
cheap tool to find resonant states in complex systems using the optical modes
of a simpler system as a basis. We apply the RSE to a photonic crystal slab in
order to identify and analyze its bound states in the continuum (BICs). We show
that the RSE is a useful and reliable method for not only finding the BICs but
also for differentiating between accidental and symmetry-protected BICs, as
well as for understanding their formation from the basis modes and evolution
with structural and material parameters of the system. The high efficiency of
the RSE allows us to track the properties of BICs and other high-quality
optical modes, covering the full parameter space of the system in a reasonable
time frame.

21
The categories of this paper are: adap-org
11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin
28
The categories of this paper are: alg-geom
4
The categories of this paper are: cond-mat
19
The categories of this paper are: eess
0
The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con
12
The categories of this paper are: nucl-th
30
The categories of this paper are: q-alg
26
The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys
16
The categories of this paper are: stat
17
The categories of this paper are: q-fin
34
The categories of this paper are: chem-ph