3,058 research outputs found
Virial statistical description of non-extensive hierarchical systems
In a first part the scope of classical thermodynamics and statistical
mechanics is discussed in the broader context of formal dynamical systems,
including computer programmes. In this context classical thermodynamics appears
as a particular theory suited to a subset of all dynamical systems. A
statistical mechanics similar to the one derived with the microcanonical
ensemble emerges from dynamical systems provided it contains, 1) a finite
non-integrable part of its phase space which is, 2) ergodic at a satisfactory
degree after a finite time. The integrable part of phase space provides the
constraints that shape the particular system macroscopical properties, and the
chaotic part provides well behaved statistical properties over a relevant
finite time. More generic semi-ergodic systems lead to intermittent behaviour,
thus may be unsuited for a statistical description of steady states. Following
these lines of thought, in a second part non-extensive hierarchical systems
with statistical scale-invariance and power law interactions are explored. Only
the virial constraint, consistent with their microdynamics, is included. No
assumptions of classical thermodynamics are used, in particular extensivity and
local homogeneity. In the limit of a large hierarchical range new constraints
emerge in some conditions that depend on the interaction law range. In
particular for the gravitational case, a velocity-site scaling relation is
derived which is consistant with the ones empirically observed in the fractal
interstellar medium.Comment: Based on the talk given at the Meeting on `Statistical Mechanics of
Non-Extensive Systems', 24-25 Oct 05, Paris. To be published in a Special
Issue of Les Comptes rendus de l'Academie des Sciences. 21 pages; 4 figure
One-loop fermionic corrections to the instanton transition in two dimensional chiral Higgs model
The one-loop fermionic contribution to the probability of an instanton
transition with fermion number violation is calculated in the chiral Abelian
Higgs model in 1+1 dimensions, where the fermions have a Yukawa coupling to the
scalar field. The dependence of the determinant on fermionic, scalar and vector
mass is determined. We show in detail how to renormalize the fermionic
determinant in partial wave analysis, which is convenient for computations.Comment: 36 pages, 5 figure
Preparing for professional practice: how well does professional training equip health and social care practitioners to engage in evidence-based practice?
This paper reports on the findings of a study that aimed to explore how relevant initial training is in relation to evidence-based practice, and explore the perceptions of recently qualified practitioners about their confidence to engage in evidence-based practice. A cross-sectional postal survey was used to ascertain the views of nurses, social workers, occupational therapists and physiotherapists who had been qualified no longer than two years prior to the survey, and had qualified at one of three London Universities. Fifty questionnaires were sent out to each professional group (a sample of 200 overall) and there was a 43% response rate achieved. The results show a clear discrepancy between what are generally positive attitudes towards evidence-based practice and the value of research evidence and the infrequency with which they actually do make use of research resources and engage in evidence-based practice. A number of constraints to engagement in accessing and utilising evidence were identified
General Monogamy Inequality for Bipartite Qubit Entanglement
We consider multipartite states of qubits and prove that their bipartite
quantum entanglement, as quantified by the concurrence, satisfies a monogamy
inequality conjectured by Coffman, Kundu, and Wootters. We relate this monogamy
inequality to the concept of frustration of correlations in quantum spin
systems.Comment: Fixed spelling mistake. Added references. Fixed error in
transformation law. Shorter and more explicit proof of capacity formula.
Reference added. Rewritten introduction and conclusion
Anomalies on Orbifolds
We discuss the form of the chiral anomaly on an S1/Z2 orbifold with chiral
boundary conditions. We find that the 4-divergence of the higher-dimensional
current evaluated at a given point in the extra dimension is proportional to
the probability of finding the chiral zero mode there. Nevertheless the
anomaly, appropriately defined as the five dimensional divergence of the
current, lives entirely on the orbifold fixed planes and is independent of the
shape of the zero mode. Therefore long distance four dimensional anomaly
cancellation ensures the consistency of the higher dimensional orbifold theory.Comment: 11 pages, latex, no figure
Gravitational anomalies in a dispersive approach
The gravitational anomalies in two dimensions, specifically the Einstein
anomaly and the Weyl anomaly, are fully determined by means of dispersion
relations. In this approach the anomalies originate from the peculiar infrared
feature of the imaginary part of the relevant formfactor which approaches a
-function singularity at zero momentum squared when .Comment: 10 page
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