Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Pseudo-surface acoustic waves in hypersonic surface phononic crystals   We present a theoretical framework allowing to properly address the nature of
surface-like eigenmodes in a hypersonic surface phononic crystal, a composite
structure made of periodic metal stripes of nanometer size and periodicity of 1
micron, deposited over a semi-infinite silicon substrate. In surface-based
phononic crystals there is no distinction between the eigenmodes of the
periodically nanostructured overlayer and the surface acoustic modes of the
semi-infinite substrate, the solution of the elastic equation being a
pseudo-surface acoustic wave partially localized on the nanostructures and
radiating energy into the bulk. This problem is particularly severe in the
hypersonic frequency range, where semi-infinite substrate's surface acoustic
modes strongly couple to the periodic overlayer, thus preventing any
perturbative approach. We solve the problem introducing a surface-likeness
coefficient as a tool allowing to find pseudo-surface acoustic waves and to
calculate their line shapes. Having accessed the pseudo-surface modes of the
composite structure, the same theoretical frame allows reporting on the gap
opening in the now well-defined pseudo-SAW frequency spectrum. We show how the
filling fraction, mass loading and geometric factors affect both the frequency
gap, and how the mechanical energy is scattered out of the surface waveguiding
modes.

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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: mtrl-th
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The categories of this paper are: atom-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: q-fin
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The categories of this paper are: patt-sol
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The categories of this paper are: cmp-lg
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-th
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The categories of this paper are: math
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The categories of this paper are: nucl-ex
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The categories of this paper are: physics
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The categories of this paper are: gr-qc
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The categories of this paper are: math-ph