A Bohmian approach to quantum fractals

A quantum fractal is a wavefunction with a real and an imaginary part continuous everywhere, but differentiable nowhere. This lack of differentiability has been used as an argument to deny the general validity of Bohmian mechanics (and other trajectory--based approaches) in providing a complete interpretation of quantum mechanics. Here, this assertion is overcome by means of a formal extension of Bohmian mechanics based on a limiting approach. Within this novel formulation, the particle dynamics is always satisfactorily described by a well defined equation of motion. In particular, in the case of guidance under quantum fractals, the corresponding trajectories will also be fractal.Comment: 19 pages, 3 figures (revised version

Singlet baryons in the graded symmetry approach to partially quenched QCD

Progress in the calculation of the electromagnetic properties of baryon excitations in lattice QCD is presenting new challenges in the determination of sea-quark loop contributions to matrix elements. A reliable estimation of the sea-quark loop contributions presents a pressing issue in the accurate comparison of lattice QCD results with experiment. In this article, an extension of the graded symmetry approach to partially quenched QCD is presented, which builds on previous theory by explicitly including flavor-singlet baryons in its construction. The formalism takes into account the interactions among both octet and singlet baryons, octet mesons, and their ghost counterparts; the latter enables the isolation of the quark-flow disconnected sea-quark loop contributions. The introduction of the flavor-singlet states anticipates the application of the method to baryon excitations such as the lowest-lying odd-parity Lambda baryon, the Lambda(1405), which is considered in detail as a worked example.Comment: arXiv copy updated to published version: Phys. Rev. D 94, 094004 (2016

Lost in hyperspace: Linearity versus exploration in the design of multimedia for independent learners

We are developing multimedia tutorials for independent learners based on a generic software shell. In doing so, one of the pedagogic issues we are addressing relates to navigation. This is a key factor in the effectiveness of multimedia teaching, since it affects how easy students find it to extract and integrate information. Multimedia tutorials tend to be either highly structured, with materials presented in a relatively linear fashion, or an encyclopedia-style explorative resource. The former is restrictive and provides the student with little freedom to study the materials in the order they choose; the latter makes systematic study difficult and students can easily become ‘lost’. Disorientation in explorative-style packages is a particular problem for Field Dependent people (Witkin et al., 1971). We have incorporated the best features of both linear and explorative packages in our shell and our tutorials, with the aim of supporting Field Dependent people as much as possible, while not denying those students who prefer to work in an explorative way the freedom to do so

Heisenberg-style bounds for arbitrary estimates of shift parameters including prior information

A rigorous lower bound is obtained for the average resolution of any estimate of a shift parameter, such as an optical phase shift or a spatial translation. The bound has the asymptotic form k_I/ where G is the generator of the shift (with an arbitrary discrete or continuous spectrum), and hence establishes a universally applicable bound of the same form as the usual Heisenberg limit. The scaling constant k_I depends on prior information about the shift parameter. For example, in phase sensing regimes, where the phase shift is confined to some small interval of length L, the relative resolution \delta\hat{\Phi}/L has the strict lower bound (2\pi e^3)^{-1/2}/, where m is the number of probes, each with generator G_1, and entangling joint measurements are permitted. Generalisations using other resource measures and including noise are briefly discussed. The results rely on the derivation of general entropic uncertainty relations for continuous observables, which are of interest in their own right.Comment: v2:new bound added for 'ignorance respecting estimates', some clarification

Pupil participation in Scottish schools: final report

This research was commissioned by Learning and Teaching Scotland (LTS) to evaluate the nature of pupil participation in primary and secondary schools across Scotland. The specific objectives of the research were: <p>· To describe what school staff and pupils understand by the term ‘pupil participation’.</p> <p>· To describe the range and usage of pupil participation mechanisms employed in schools.</p> <p>· To describe how school staff respect and respond to pupils’ views and ideas, and those of the wider community.</p> <p>· To identify the characteristics of schools and classrooms that facilitate effective pupil participation.</p> <p>· To identify possible barriers to the development of pupil participation in schools and to make suggestions about how these can be overcome.</p> <p>· To capture examples of effective practice of pupil participation.</p> <p>· To make suggestions about how pupil participation can help support the implementation of the Curriculum for Excellence.</p&gt

Low frequency electrical noise across contacts between a normal conductor and superconducting bulk YBa2Cu3O7

Virtually every device that makes use of the new ceramic superconductors will need normal conductor to supercondutor contacts. The current-voltage and electrical noise characteristics of these contacts could be become important design considerations. I-V and low frequency electrical noise measurements are presented on contacts between a normal conductor and superconducting polycrystalline YBa2Cu3O7. The contacts were formed by first sputtering gold palladium pads onto the surface of the bulk superconductor and then using silver epoxy to attach a wire(s) to each pad. Voltage across the contacts was found for small current densities. The voltage spectral density, S sub v(f), a quanity often used to characterize electrical noise, very closely followed an empirical relationship given by, S sub v(f) = C(VR)sq/f, where V is the DC voltage across the contact, R is the contact resistance, F is frequency, and C is a contant found to be 2 x 10(exp -10)/Omega sq at 78 K. This relationship was found to be independent of contact area, contact geometry, sample fabrication technique, and sample density