2,412 research outputs found
Regular Tunnelling Sequences in Mixed Systems
We show that the pattern of tunnelling rates can display a vivid and regular
pattern when the classical dynamics is of mixed chaotic/regular type. We
consider the situation in which the dominant tunnelling route connects to a
stable periodic orbit and this orbit is surrounded by a regular island which
supports a number of quantum states. We derive an explicit semiclassical
expression for the positions and tunnelling rates of these states by use of a
complexified trace formula.Comment: submitted to Physica E as a contribution to the workshop proceedings
of "Dynamics of Complex Systems" held at the Max Planck Institute for the
Physics of Complex Systems in Dresden from March 30 to June 15, 199
Scarring and the statistics of tunnelling
We show that the statistics of tunnelling can be dramatically affected by
scarring and derive distributions quantifying this effect. Strong deviations
from the prediction of random matrix theory can be explained quantitatively by
modifying the Gaussian distribution which describes wavefunction statistics.
The modified distribution depends on classical parameters which are determined
completely by linearised dynamics around a periodic orbit. This distribution
generalises the scarring theory of Kaplan [Phys. Rev. Lett. {\bf 80}, 2582
(1998)] to describe the statistics of the components of the wavefunction in a
complete basis, rather than overlaps with single Gaussian wavepackets. In
particular it is shown that correlations in the components of the wavefunction
are present, which can strongly influence tunnelling-rate statistics. The
resulting distribution for tunnelling rates is tested successfully on a
two-dimensional double-well potential.Comment: 20 pages, 4 figures, submitted to Ann. Phy
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Thesis (Ed.M.)--Boston Universit
Clinical solutions: not always what they seem?
Brenner and colleagues, in their article published in Critical Care, showed elevated levels of the reactive carbonyl species (RCS) methylglyoxal (MG) in the circulation of patients with septic shock. We commend the authors’ bravery in launching this molecule into a field well-populated with biomarkers and where clinical diagnosis persists as the ‘gold standard’
Applying a social justice framework to ensure good practice in monitoring student learning engagement
A current Australian Learning and Teaching Council (ALTC) funded action research project aims to provide a set of practical resources founded on a social justice framework, to guide good practice for monitoring student learning engagement (MSLE) in higher education. The project involves ten Australasian institutions, eight of which are engaged in various MSLE type projects. A draft framework, consisting of six social justice principles which emerged from the literature has been examined with reference to the eight institutional approaches for MSLE in conjunction with the personnel working on these initiatives during the first action research cycle. The cycle will examine the strategic and operational implications of the framework in each of the participating institutions. Cycle 2 will also build capacity to embed the principles within the institutional MSLE program and will identify and collect examples and resources that exemplify the principles in practice. The final cycle will seek to pilot the framework to guide new MSLE initiatives. In its entirety, the project will deliver significant resources to the sector in the form of a social justice framework for MSLE, guidelines and sector exemplars for MSLE. As well as increasing the awareness amongst staff around the criticality of transition to university (thereby preventing attrition) and the significance of the learning and teaching agenda in enhancing student engagement, the project will build leadership capacity within the participating institutions and provide a knowledge base and institutional capacity for the Australasian HE sector to deploy the deliverables that will safeguard student learning engagement At this early stage of the project the workshop session provides an opportunity to discuss and examine the draft set of social justice principles and to discuss their potential value for the participants’ institutional contexts. Specifically, the workshop will explore critical questions associated with the principles
A Matrix Element for Chaotic Tunnelling Rates and Scarring Intensities
It is shown that tunnelling splittings in ergodic double wells and resonant
widths in ergodic metastable wells can be approximated as easily-calculated
matrix elements involving the wavefunction in the neighbourhood of a certain
real orbit. This orbit is a continuation of the complex orbit which crosses the
barrier with minimum imaginary action. The matrix element is computed by
integrating across the orbit in a surface of section representation, and uses
only the wavefunction in the allowed region and the stability properties of the
orbit. When the real orbit is periodic, the matrix element is a natural measure
of the degree of scarring of the wavefunction. This scarring measure is
canonically invariant and independent of the choice of surface of section,
within semiclassical error. The result can alternatively be interpretated as
the autocorrelation function of the state with respect to a transfer operator
which quantises a certain complex surface of section mapping. The formula
provides an efficient numerical method to compute tunnelling rates while
avoiding the need for the exceedingly precise diagonalisation endemic to
numerical tunnelling calculations.Comment: Submitted to Annals of Physics. This work has been submitted to
Academic Press for possible publicatio
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