Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spontaneous magnon decays in planar ferromagnet   We predict that spin-waves in an easy-plane ferromagnet have a finite
lifetime at zero temperature due to spontaneous decays. In zero field the
damping is determined by three-magnon decay processes, whereas decays in the
two-particle channel dominate in a transverse magnetic field. Explicit
calculations of the magnon damping are performed in the framework of the
spin-wave theory for the $XXZ$ square-lattice ferromagnet with an anisotropy
parameter $\lambda<1$. In zero magnetic field the decays occur for
$\lambda^*<\lambda<1$ with $\lambda^*\approx 1/7$. We also discuss possibility
of experimental observation of the predicted effect in a number of
ferromagnetic insulators.

15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
16
The categories of this paper are: stat
32
The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
21
The categories of this paper are: adap-org
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
27
The categories of this paper are: comp-gas
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The categories of this paper are: acc-phys
1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th
26
The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph
25
The categories of this paper are: patt-sol