294,221 research outputs found
Vector chiral states in low-dimensional quantum spin systems
A class of exact spin ground states with nonzero averages of vector spin
chirality, , is presented. It is
obtained by applying non-uniform O(2) rotations of spin operators in the XY
plane on the SU(2)-invariant Affleck-Kennedy-Lieb-Tasaki (AKLT) states and
their parent Hamiltonians. Excitation energies of the new ground states are
studied with the use of single-mode approximation in one dimension for S=1. The
excitation gap remains robust. Construction of chiral AKLT states is shown to
be possible in higher dimensions. We also present a general idea to produce
vector chirality-condensed ground states as non-uniform O(2) rotations of the
non-chiral parent states. Dzyaloshinskii-Moriya interaction is shown to imply
non-zero spin chirality.Comment: 4 pages, 1 figur
Extraction of information about periodic orbits from scattering functions
As a contribution to the inverse scattering problem for classical chaotic
systems, we show that one can select sequences of intervals of continuity, each
of which yields the information about period, eigenvalue and symmetry of one
unstable periodic orbit.Comment: LaTeX, 13 pages (includes 5 eps-figures
Pointwise asymptotic behavior of modulated periodic reaction-diffusion waves
By working with the periodic resolvent kernel and Bloch-decomposition, we
establish pointwise bounds for the Green function of the linearized equation
associated with spatially periodic traveling waves of a system of reaction
diffusion equations.With our linearized estimates together with a nonlinear
iteration scheme developed by Johnson-Zumbrun, we obtain - behavior() of a nonlinear solution to a perturbation equation of a
reaction-diffusion equation with respect to initial data in
recovering and slightly sharpening results obtained by Schneider using weighted
energy and renormalization techniques. We obtain also pointwise nonlinear
estimates with respect to two different initial perturbations and , respectively,
sufficiently small and sufficiently large, showing that behavior is that
of a heat kernel. These pointwise bounds have not been obtained elsewhere, and
do not appear to be accessible by previous techniques
Coupling of phonons and spin waves in triangular antiferromagnet
We investigate the influence of the spin-phonon coupling in the triangular
antiferromagnet where the coupling is of the exchange-striction type. The
magnon dispersion is shown to be modified significantly at wave vector (2pi,0)
and its symmetry-related points, exhibiting a roton-like minimum and an
eventual instability in the dispersion. Various correlation functions such as
equal-time phonon correlation, spin-spin correlation, and local magnetization
are calculated in the presence of the coupling.Comment: 6 pages, 5 figures; references added, minor text revisions, submitted
to PR
- …