Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Enhanced group velocity in metamaterials   The Bruggeman formalism is implemented to estimate the refractive index of an
isotropic, dielectric, homogenized composite medium (HCM). Invoking the
well--known Hashin--Shtrikman bounds, we demonstrate that the group velocity in
certain HCMs can exceed the group velocities in their component materials. Such
HCMs should therefore be considered as metamaterials.

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The categories of this paper are: q-alg
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-th
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The categories of this paper are: funct-an
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The categories of this paper are: quant-ph
9
The categories of this paper are: nlin
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The categories of this paper are: atom-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: supr-con
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The categories of this paper are: acc-phys
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The categories of this paper are: math
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The categories of this paper are: nucl-th
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The categories of this paper are: gr-qc
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The categories of this paper are: econ
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The categories of this paper are: cmp-lg