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Current-induced torques in textured Rashba ferromagnets
In systems with small spin-orbit coupling, current-induced torques on the
magnetization require inhomogeneous magnetization textures. For large
spin-orbit coupling, such torques exist even without gradients in the
magnetization direction. Here, we consider current-induced torques in
ferromagnetic metals with both Rashba spin-orbit coupling and inhomogeneous
magnetization. We first phenomenologically construct all torques that are
allowed by the symmetries of the system, to first order in
magnetization-direction gradients and electric field. Second, we use a
Boltzmann approach to calculate the spin torques that arise to second order in
the spin-orbit coupling. We apply our results to current-driven domain walls
and find that the domain-wall mobility is strongly affected by torques that
result from the interplay between spin-orbit coupling and inhomogeneity of the
magnetization texture.Comment: 9 pages, 3 figure
Correspondence: No substantial long-term bias in the Cenozoic benthic foraminifera oxygen-isotope record
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DESIGNING FOR THE DEEPEST NEEDS OF BOTH PUBLIC SERVICE CONSUMERS AND PROVIDERS; INNOVATION IN MENTAL HEALTH CRISIS RESPONSE
Anomalous Hall conductivity from the dipole mode of spin-orbit-coupled cold-atom systems
Motivated by recent experiments [Lin {\it et al.}, Nature {\bf 417}, 83
(2011)] that engineered spin-orbit coupling in ultra-cold mixtures of bosonic
atoms, we study the dipole oscillation of trapped spin-orbit-coupled
non-condensed Bose and Fermi gases. We find that different directions of
oscillation are coupled by the spin-orbit interactions. The phase difference
between oscillatory motion in orthogonal directions and the trapping
frequencies of the modes are shown to be related to the anomalous Hall
conductivity. Our results can be used to experimentally determine the anomalous
Hall conductivity for cold-atom systems.Comment: 4 pages, 2 figure
Talking quiescence: a rigorous theory that supports parallel composition, action hiding and determinisation
The notion of quiescence - the absence of outputs - is vital in both
behavioural modelling and testing theory. Although the need for quiescence was
already recognised in the 90s, it has only been treated as a second-class
citizen thus far. This paper moves quiescence into the foreground and
introduces the notion of quiescent transition systems (QTSs): an extension of
regular input-output transition systems (IOTSs) in which quiescence is
represented explicitly, via quiescent transitions. Four carefully crafted rules
on the use of quiescent transitions ensure that our QTSs naturally capture
quiescent behaviour.
We present the building blocks for a comprehensive theory on QTSs supporting
parallel composition, action hiding and determinisation. In particular, we
prove that these operations preserve all the aforementioned rules.
Additionally, we provide a way to transform existing IOTSs into QTSs, allowing
even IOTSs as input that already contain some quiescent transitions. As an
important application, we show how our QTS framework simplifies the fundamental
model-based testing theory formalised around ioco.Comment: In Proceedings MBT 2012, arXiv:1202.582
An adaptive and strategic human-centred design approach to shaping pandemic design education that promotes wellbeing
Positive student wellbeing is intrinsically connected to positive learning outcomes. Students learn more when they feel well, and the way we shape education influences the way students feel. The COVID-19 crisis has forced us to radically change our design education and is having a large impact on student wellbeing and learning. While some students manage well to adapt to the new circumstances, others struggle and face challenges such as risk of burnout, lack of motivation, and social isolation. In this paper we describe how we approached this challenge by applying methods and principles from strategic human-centred design and systems thinking. The strategic design approach included researching values and patterns in student and staff experiences. The systems approach meant that we saw the university as a complex adaptive system, which focused our activities on connecting staff and students who were and are running multiple creative experiments to promote student wellbeing. This approach is strategic because it supports continuous design and implementation of initiatives to promote wellbeing. While this is work in progress, we here present a number of design principles that we developed through this work that enable future designs that promote student wellbeing in (pandemic) higher education
Spin Excitations and Sum Rules in the Heisenberg Antiferromagnet
Various bounds for the energy of collective excitations in the Heisenberg
antiferromagnet are presented and discussed using the formalism of sum rules.
We show that the Feynman approximation significantly overestimates (by about
30\% in the square lattice) the spin velocity due to the non
negligible contribution of multi magnons to the energy weighted sum rule. We
also discuss a different, Goldstone type bound depending explicitly on the
order parameter (staggered magnetization). This bound is shown to be
proportional to the dispersion of classical spin wave theory with a
q-independent normalization factor. Rigorous bounds for the excitation energies
in the anisotropic Heisenberg model are also presented.Comment: 26 pages, Plain TeX including 1 PostScript figure, UTF-307-10/9
Quantized vortices and collective oscillations of a trapped Bose condensed gas
Using a sum rule approach we calculate the frequency shifts of the quadrupole
oscillations of a harmonically trapped Bose gas due to the presence of a
quantized vortex. Analytic results are obtained for positive scattering lengths
and large N where the shift relative to excitations of opposite angular
momentum is found to be proportional to the quantum circulation of the vortex
and to decrease as N^{-2/5}. Results are also given for smaller values of N
covering the transition between the ideal gas and the Thomas-Fermi limit. For
negative scattering lengths we predict a macroscopic instability of the vortex.
The splitting of the collective frequencies in toroidal configurations is also
discussed.Comment: Rextex, 4 pages, 1 postscript figur
Patterns of LRF in elderly HNSCCpatients treated with definitive RT in relation to dose distribution
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