34 research outputs found
Spectral Measures and Generating Series for Nimrep Graphs in Subfactor Theory II: SU(3)
We complete the computation of spectral measures for SU(3) nimrep graphs
arising in subfactor theory, namely the SU(3) ADE graphs associated with SU(3)
modular invariants and the McKay graphs of finite subgroups of SU(3). For the
SU(2) graphs the spectral measures distill onto very special subsets of the
semicircle/circle, whilst for the SU(3) graphs the spectral measures distill
onto very special subsets of the discoid/torus. The theory of nimreps allows us
to compute these measures precisely. We have previously determined spectral
measures for some nimrep graphs arising in subfactor theory, particularly those
associated with all SU(2) modular invariants, all subgroups of SU(2), the
torus, SU(3), and some SU(3) graphs.Comment: 38 pages, 21 figure
Wormholes in AdS
We construct a few Euclidean supergravity solutions with multiple boundaries.
We consider examples where the corresponding boundary field theory is well
defined on each boundary. We point out that these configurations are puzzling
from the AdS/CFT point of view. A proper understanding of the AdS/CFT
dictionary for these cases might yield some information about the physics of
closed universes.Comment: 38 pages, 2 figures, harvmac. v2: minor typos corrected and
references adde
DOMAIN STRUCTURE IN HELICAL MAGNETS
For a helical magnet the axis of the helix is a hard axis in most materials but the moments are never constrained so completely. Without that restriction the moments have two degrees of freedom. The two appropriate equations of motion are derived and it is show in the continuum approximation that within a domain a modulated structure is predicted for the variation of the out-of-plane angle, as found experimentally. The domain walls are probably similar in width to those in which the moments are constrained
Advances in the fatigue assessment of wire ropes
This paper presents the findings from an in-depth analysis of the (axial) stiffness data recorded during tension-tension fatigue tests on wire ropes, particularly in relation to how changes in stiffness during testing relate to changes in rope strength. A linear relationship between stiffness and strength is shown to exist and a methodology presented for quantifying residual strength with applied cycles. New lower bound fatigue lines for six-strand rope and spiral strand are presented which are based on a 10% loss of strength. These new lines have the advantage of having been established using a common discard criterion for wire ropes
Pinning theory of domain walls in helical magnets
The theory of elasticity and pinning of domain walls in helical magnets is
presented. Domain walls perpendicular to the helical axis show non-local
elasticity and are marginally pinned by local disorder. Weak anisotropy
combined with magnetic dilution leads however to a non-local bulk pinning
effect. Domain walls with other orientations include generically vortex arrays,
similar to type-II superconductors. Their pinning force is calculated as a
function of wall orientation, pitch angle and impurity concentration. It is
shown that metastable domains can vary between needle and pancake like shape.Comment: The paper has been withdrawn due to change of format and some
correction