Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Scattering of phonons on two-level systems in disordered crystals   We calculate the scattering rates of phonons on two-level systems in
disordered trigonal and hexagonal crystals. We apply a model in which the
two-level system, characterized by a direction in space, is coupled to the
strain field of the phonon via a tensor of coupling constants. The structure of
the tensor of coupling constants is similar to the structure of the tensor of
elastic stiffness constants, in the sense that they are determined by the same
symmetry transformations. In this way, we emphasize the anisotropy of the
interaction of elastic waves with the ensemble of two-level systems in
disordered crystals. We also point to the fact that the ratio
$\gamma_l/\gamma_t$ has a much broader range of allowed values in disordered
crystals than in isotropic solids.

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The categories of this paper are: hep-th
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The categories of this paper are: q-bio
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The categories of this paper are: eess
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The categories of this paper are: solv-int
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The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
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The categories of this paper are: dg-ga
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The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: nlin
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The categories of this paper are: patt-sol
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The categories of this paper are: atom-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: math-ph