Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electromagnetic energy and energy flows in photonic crystals made of
  arrays of parallel dielectric cylinders   We consider the electromagnetic propagation in two-dimensional photonic
crystals, formed by parallel dielectric cylinders embedded a uniform medium.
The frequency band structure is computed using the standard plane-wave
expansion method, and the corresponding eigne-modes are obtained subsequently.
The optical flows of the eigen-modes are calculated by a direct computation
approach, and several averaging schemes of the energy current are discussed.
The results are compared to those obtained by the usual approach that employs
the group velocity calculation. We consider both the case in which the
frequency lies within passing band and the situation in which the frequency is
in the range of a partial bandgap. The agreements and discrepancies between
various averaging schemes and the group velocity approach are discussed in
detail. The results indicate the group velocity can be obtained by appropriate
averaging method.

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The categories of this paper are: plasm-ph
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The categories of this paper are: patt-sol
16
The categories of this paper are: stat
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The categories of this paper are: cmp-lg
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The categories of this paper are: econ
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The categories of this paper are: atom-ph
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The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
10
The categories of this paper are: q-bio
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The categories of this paper are: supr-con
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The categories of this paper are: q-alg
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The categories of this paper are: nlin
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The categories of this paper are: adap-org
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The categories of this paper are: mtrl-th
12
The categories of this paper are: nucl-th
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The categories of this paper are: nucl-ex