Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Liquid Surface Wave Band Structure Instabilities   We study interfacial instabilities between two spatially periodically sheared
ideal fluids. Bloch wavefunction decompositions of the surface deformation and
fluid velocities result in a nonhermitian secular matrix with an associated
band structure that yields both linear oscillating and nonoscillating
instabilities, enhanced near Bragg planes corresponding to the periodicity
determined by converging or diverging surface flows. The instabilities persist
even when the dynamical effects of the upper fluid are neglected, in contrast
to the uniform shear Kelvin-Helmholtz (KH) instability. Periodic flows can also
couple with uniform shear and suppress standard KH instabilities.

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The categories of this paper are: comp-gas
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The categories of this paper are: supr-con
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The categories of this paper are: physics
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The categories of this paper are: alg-geom
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The categories of this paper are: q-alg
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The categories of this paper are: nucl-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-ph
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The categories of this paper are: math-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: funct-an
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The categories of this paper are: astro-ph
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The categories of this paper are: nlin
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The categories of this paper are: hep-th
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The categories of this paper are: hep-ex
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The categories of this paper are: cmp-lg