385 research outputs found
Unital Dilations of Completely Positive Semigroups
Dilations of completely positive semigroups to endomorphism semigroups have
been studied by numerous authors. Most existing dilation theorems involve a
non-unital embedding, corresponding to the embedding of as a corner of
for Hilbert spaces . A 1986 paper of Jean-Luc Sauvageot
shows how to achieve a unital dilation, but does not specify how to do so while
also preserving continuity properties of the original semigroup. This thesis
further develops Sauvageot's dilation theory in order to establish the
existence of continuous unital dilations, and to explore connections with free
probability.Comment: 171 pages. Ph. D. thesis; upon graduation, will be published by
ProQuest in cooperation with The University of Iow
Unital Dilations of Completely Positive Semigroups: From Combinatorics to Continuity
Using ideas due to Jean-Luc Sauvageot, we prove the existence of a continuous
unital dilation of a CP-semigroup on a separable W-algebra. This paper
presents the material in the author's Ph. D. thesis (arXiv.org:1304.0134.pdf)
with some generalizations and an improved exposition.Comment: 69 pages. Submitted to Memoirs of the AM
p-wave Feshbach molecules
We have produced and detected molecules using a p-wave Feshbach resonance
between 40K atoms. We have measured the binding energy and lifetime for these
molecules and we find that the binding energy scales approximately linearly
with magnetic field near the resonance. The lifetime of bound p-wave molecules
is measured to be 1.0 +/- 0.1 ms and 2.3 +/- 0.2 ms for the m_l = +/- 1 and m_l
= 0 angular momentum projections, respectively. At magnetic fields above the
resonance, we detect quasi-bound molecules whose lifetime is set by the
tunneling rate through the centrifugal barrier
The potential energy of a K Fermi gas in the BCS-BEC crossover
We present a measurement of the potential energy of an ultracold trapped gas
of K atoms in the BCS-BEC crossover and investigate the temperature
dependence of this energy at a wide Feshbach resonance, where the gas is in the
unitarity limit. In particular, we study the ratio of the potential energy in
the region of the unitarity limit to that of a non-interacting gas, and in the
T=0 limit we extract the universal many-body parameter . We find ; this value is consistent with previous measurements
using Li atoms and also with recent theory and Monte Carlo calculations.
This result demonstrates the universality of ultracold Fermi gases in the
strongly interacting regime
Robotic Resistance Treadmill Training Improves Locomotor Function in Children With Cerebral Palsy: A Randomized Controlled Pilot Study
Objective To determine whether applying controlled resistance forces to the legs during the swing phase of gait may improve the efficacy of treadmill training as compared with applying controlled assistance forces in children with cerebral palsy (CP). Design Randomized controlled study. Setting Research unit of a rehabilitation hospital. Participants Children with spastic CP (N=23; mean age, 10.6y; range, 6–14y; Gross Motor Function Classification System levels, I–IV). Interventions Participants were randomly assigned to receive controlled assistance (n=11) or resistance (n=12) loads applied to the legs at the ankle. Participants underwent robotic treadmill training 3 times a week for 6 weeks (18 sessions). A controlled swing assistance/resistance load was applied to both legs starting from the toe-off to mid-swing phase of gait during training. Main Outcome Measures Outcome measures consisted of overground walking speed, 6-minute walk distance, and Gross Motor Function Measure scores and were assessed pre and post 6 weeks of training and 8 weeks after the end of training. Results After 6 weeks of treadmill training in participants from the resistance training group, fast walking speed and 6-minute walk distance significantly improved (18% and 30% increases, respectively), and 6-minute walk distance was still significantly greater than that at baseline (35% increase) 8 weeks after the end of training. In contrast, overground gait speed and 6-minute walk distance had no significant changes after robotic assistance training. Conclusions The results of the present study indicated that robotic resistance treadmill training is more effective than assistance training in improving locomotor function in children with CP
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