Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Possible Realization of Optical Quadratic and Dirac Points in Woodpile
  Photonic Crystals   The simulation of fermionic relativistic physics, e.g., Dirac and Weyl
physics, has led to the discovery of many unprecedented phenomena in photonics,
of which the optical-frequency realization is, however, still challenging.
Here, surprisingly, we discover that the woodpile photonic crystals commonly
used for optical frequency applications host exotic fermion-like relativistic
degeneracies: a Dirac nodal line and a fourfold quadratic point, as protected
by the nonsymmorphic crystalline symmetry. Deforming the woodpile photonic
crystal leads to the emergence of type-II Dirac points from the fourfold
quadratic point. Such type-II Dirac points can be detected by its anomalous
refraction property which is manifested as a giant birefringence in a slab
setup. Our findings provide a promising route towards 3D optical Dirac physics
in all-dielectric photonic crystals.

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The categories of this paper are: hep-ex
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The categories of this paper are: q-bio
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The categories of this paper are: math
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The categories of this paper are: quant-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: solv-int
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The categories of this paper are: nlin
0
The categories of this paper are: hep-ph
28
The categories of this paper are: alg-geom
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The categories of this paper are: acc-phys
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The categories of this paper are: supr-con
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The categories of this paper are: bayes-an
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The categories of this paper are: q-fin
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The categories of this paper are: stat
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The categories of this paper are: cs
30
The categories of this paper are: q-alg