Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Asymptotic approximations for the plasmon resonances of nearly touching
  spheres   Excitation of surface-plasmon resonances of closely spaced nanometallic
structures is a key technique used in nanoplasmonics to control light on
subwavelength scales and generate highly confined electric-field hotspots. In
this paper we develop asymptotic approximations in the near-contact limit for
the entire set of surface-plasmon modes associated with the prototypical sphere
dimer geometry. Starting from the quasi-static plasmonic eigenvalue problem, we
employ the method of matched asymptotic expansions between a gap region, where
the boundaries are approximately paraboloidal, pole regions within the spheres
and close to the gap, and a particle-scale region where the spheres appear to
touch at leading order. For those modes that are strongly localised to the gap,
relating the gap and pole regions gives a set of effective eigenvalue problems
formulated over a half space representing one of the poles. We solve these
problems using integral transforms, finding asymptotic approximations, singular
in the dimensionless gap width, for the eigenvalues and eigenfunctions. In the
special case of modes that are both axisymmetric and odd about the plane
bisecting the gap, where matching with the outer region introduces a
logarithmic dependence upon the dimensionless gap width, our analysis follows
[O. Schnitzer, \textit{Physical Review B}, \textbf{92} 235428 2015]. We also
analyse the so-called anomalous family of even modes, characterised by field
distributions excluded from the gap. We demonstrate excellent agreement between
our asymptotic formulae and exact calculations.

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The categories of this paper are: ao-sci
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The categories of this paper are: hep-lat
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The categories of this paper are: nucl-ex
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The categories of this paper are: alg-geom
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The categories of this paper are: gr-qc
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The categories of this paper are: eess
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The categories of this paper are: bayes-an
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The categories of this paper are: nucl-th
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The categories of this paper are: solv-int
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The categories of this paper are: chem-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: patt-sol
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The categories of this paper are: nlin
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The categories of this paper are: q-fin
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The categories of this paper are: q-alg
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The categories of this paper are: stat