Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Phonons in honeycomb and auxetic two-dimensional lattices   The modes of vibrations in honeycomb and auxetic structures are studied, with
models in which the lattice is represented by a planar network where sites are
connected by strings and rigid rods. The auxetic network is obtained modifying
a model proposed by Evans et al. in 1991, and used to explain the negative
Poisson's ratio of auxetic materials. This relevant property means that the
materials have a lateral extension, instead to shrink, when they are stretched.
For what concerns the acoustic properties of these structures, they absorb
noise and vibrations more efficiently than non-auxetic equivalents. The
acoustic and optical dispersions obtained in the case of the auxetic model are
compared with the dispersions displayed by a conventional honeycomb network. It
is possible to see that the phonon dispersions of the auxetic model possess a
complete bandgap and that the Goldstone mode group velocity is strongly
dependent on the direction of propagation. The presence of a complete bandgap
can explain some experimental observations on the sound propagation properties
of the auxetic materials.

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The categories of this paper are: solv-int
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The categories of this paper are: q-alg
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The categories of this paper are: q-bio
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The categories of this paper are: q-fin
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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-ex
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The categories of this paper are: stat
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The categories of this paper are: supr-con
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The categories of this paper are: adap-org
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The categories of this paper are: comp-gas
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The categories of this paper are: atom-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: chem-ph
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The categories of this paper are: hep-th
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The categories of this paper are: astro-ph
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The categories of this paper are: hep-lat