Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dynamical magneto-electric coupling in helical magnets   Collective mode dynamics of the helical magnets coupled to electric
polarization via spin-orbit interaction is studied theoretically. The soft
modes associated with the ferroelectricity are not the transverse optical
phonons, as expected from the Lyddane-Sachs-Teller relation, but are the spin
waves hybridized with the electric polarization. This leads to the Drude-like
dielectric function $\epsilon(\omega)$ in the limit of zero magnetic
anisotropy. There are two more low-lying modes; phason of the spiral and
rotation of helical plane along the polarization axis. The roles of these soft
modes in the neutron scattering and antiferromagnetic resonance are revealed,
and a novel experiment to detect the dynamical magneto-electric coupling is
proposed.

29
The categories of this paper are: funct-an
28
The categories of this paper are: alg-geom
2
The categories of this paper are: math
16
The categories of this paper are: stat
24
The categories of this paper are: dg-ga
6
The categories of this paper are: astro-ph
3
The categories of this paper are: physics
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
19
The categories of this paper are: eess
12
The categories of this paper are: nucl-th
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
26
The categories of this paper are: bayes-an
23
The categories of this paper are: solv-int
0
The categories of this paper are: hep-ph