Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A generalized model of magnon kinetics and subgap magnetic noise   Magnetic noise spectroscopy provides a noninvasive probe of spin dynamics in
magnetic materials. We consider two-dimensional magnetically ordered insulators
with magnon excitations, especially those supporting long-distance magnon
transport, where nitrogen-vacancy (NV) centers enable the access to (nearly)
ballistic transport regime of magnons. We develop a generalized theory to
describe the magnon transport across a wide range of length scales. The
longitudinal dynamic spin susceptibility is derived from the Boltzmann equation
and extended to a Lindhard form, which is modified by both the spin-conserving
magnon collisions and spin relaxation. Our result is consistent with the
diffusive (ballistic) model for the length scale much larger (smaller) than the
magnon mean free path, and provides a description for the intermediate regime.
We also give a prediction for the NV transition rate in different magnon
transport regimes.

19
The categories of this paper are: eess
9
The categories of this paper are: nlin
1
The categories of this paper are: cs
25
The categories of this paper are: patt-sol
20
The categories of this paper are: acc-phys
26
The categories of this paper are: bayes-an
13
The categories of this paper are: quant-ph
29
The categories of this paper are: funct-an
32
The categories of this paper are: atom-ph
34
The categories of this paper are: chem-ph
27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
36
The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc
28
The categories of this paper are: alg-geom
17
The categories of this paper are: q-fin