Vector Positronium States in QED3

The homogeneous Bethe-Salpeter equation is solved in the quenched ladder approximation for the vector positronium states of 4-component quantum electrodynamics in 2 space and 1 time dimensions. Fermion propagator input is from a Rainbow approximation Dyson-Schwinger solution, with a broad range of fermion masses considered. This work is an extension of earlier work on the scalar spectrum of the same model. The non-relativistic limit is also considered via the large fermion mass limit. Classification of states via their transformation properties under discrete parity transformations allows analogies to be drawn with the meson spectrum of QCD.Comment: 24 pages, 2 encapsulated postscript figure

The analytic structure of heavy quark propagators

The renormalised quark Dyson-Schwinger equation is studied in the limit of the renormalised current heavy quark mass m_R --> infinity. We are particularly interested in the analytic pole structure of the heavy quark propagator in the complex momentum plane. Approximations in which the quark-gluon vertex is modelled by either the bare vertex or the Ball-Chiu Ansatz, and the Landau gauge gluon propagator takes either a gaussian form or a gaussian form with an ultraviolet asymptotic tail are used.Comment: 21 pages Latex and 5 postscript figures. The original version of this paper has been considerably extended to include a formalism dealing with the renormalised heavy quark Dyson-Schwinger equation and uses a more realistic Ansatz for the gluon propagator

Nonperturbative Vertices in Supersymmetric Quantum Electrodynamics

We derive the complete set of supersymmetric Ward identities involving only two- and three- point proper vertices in supersymmetric QED. We also present the most general form of the proper vertices consistent with both the supersymmetric and U(1) gauge Ward identities. These vertices are the supersymmetric equivalent of the non supersymmetric Ball-Chiu vertices.Comment: seventeen pages late

Researching Bradford: A review of social research on Bradford District

A synthesis of findings from social research on the District of Bradford. This report synthesises the findings from a wide range of social research undertaken on the District of Bradford, primarily between 1995 and 2005. The researchers reviewed almost 200 pieces of work. The key results are summarised under thematic headings: - The social, economic and institutional context - Community cohesion - Housing, neighbourhoods and regeneration - Business and enterprise - Health, disability and social care - Children and young people - Education, skills and the labour market - Crime and community safety It also identifies a future research agenda. The main purpose of the review was to provide the Joseph Rowntree Foundation and local organisations in Bradford with a firm basis upon which to build future work in the District

A Quark-Antiquark Condensate in Three-Dimensional QCD

Three-dimensional lattice QCD is studied by Monte Carlo simulations within the quenched approximation. At zero temperature a quark-antiquark condensate is observed in the limit of vanishing quark masses. The condensate vanishes continuously at the finite-temperature deconfinement phase transition of the theory. A natural interpretation of this phenomenon in the full theory with dynamical quarks is in terms of the spontaneous flavor symmetry breaking $U(N_f) \to U(N_f/2)\times U(N_f/2)$. In addition, the spectrum of low-lying Dirac operator eigenvalues is computed and found to be consistent with a flat distribution at zero temperature, in agreement with analytical predictions.Comment: Extensive revision of the original version. 11 pages, 6 figures included as EPS files. The problem with figure encapsulation fixe

Mass singularity and confining property in QED3QED_3

We discuss the properties of the position space fermion propagator in three dimensional QED which has been found previouly based on Ward-Takahashi-identity for soft-photon emission vertex and spectral representation.There is a new type of mass singularity which governs the long distance behaviour.It leads the propagator vanish at large distance.This term corresponds to dynamical mass in position space.Our model shows confining property and dynamical mass generation for arbitrary coupling constant.Since we used dispersion retation in deriving spectral function there is a physical mass which sets a mass scale.For finite cut off we obtain the full propagator in the dispersion integral as a superposition of different massses.Low energy behaviour of the proagator is modified to decrease by position dependent mass.In the limit of zero infrared cut-off the propagator vanishes with a new kind of infrared behaviour.Comment: 22pages,4figures,revtex4,Notational sloppiness are crrected.Submitted to JHE

Constructing the fermion-boson vertex in QED3

We derive perturbative constraints on the transverse part of the fermion-boson vertex in massive QED3 through its one loop evaluation in an arbitrary covariant gauge. Written in a particular form, these constraints naturally lead us to the first non-perturbative construction of the vertex, which is in complete agreement with its one loop expansion in all momentum regimes. Without affecting its one-loop perturbative properties, we also construct an effective vertex in such a way that the unknown functions defining it have no dependence on the angle between the incoming and outgoing fermion momenta. Such a vertex should be useful for the numerical study of dynamical chiral symmetry breaking, leading to more reliable results.Comment: 13 pages, 2 figure

FieldscapesVR: Virtual world field trips to extend and enrich field teaching

Field teaching is an indispensable feature of geoscience education, at all levels. However, delivering effective field experiences is challenging under many circumstances – not least for distance students such as Open University (OU) undergraduates. Hence, OU geoscience modules over the last 25 years have featured virtual field trips (VFTs), exploiting a range of formats, typically delivered via CD-ROM, DVD or web browser. 2013 saw a dramatic reboot with the launch of Virtual Skiddaw, a field exercise framed in a multi-user virtual environment that was created using 3D gaming software (Unity 3D). Virtual world field trips (VWFTs) offer a wealth of new opportunities for online field learning. Advances in scanning and photogrammetry make detailed observation possible, while the digital landscape and ambient audio foster immersion. Rather than merely trying to replicate an outdoor field trip, the VWFT can also go ‘beyond fieldwork’: users can access aerial perspectives; drape the digital landscape with different imagery (e.g. maps); teleport and fly to save time; call up subsurface cross-sections; even fade other avatars out if they are obscuring the view! The multi-user capability enables collaborative work, even among groups that are widely dispersed, as OU students are. There are times when a VFT can replace physical fieldwork, for example for those who cannot access the outdoor locations. However, we regard their primary role as support for physical field teaching, so that students can make the most of their, often limited, time in the field: pre-trip familiarisation and orientation, followed by post-trip revision, reflection or extension – for both educators and students; introducing basic fieldwork concepts and logistics, risk assessment, and even some fieldwork skills – for instance to students with no prior field experience – to alleviate anxiety and build confidence. For example, in Virtual Skiddaw both mapwork and compass skills can be practised in the context of a 3D landscape. VWFTs also facilitate development of spatial literacy skills by bridging the 2D/3D conceptual gap, promote active learning, foster collaborative skills and reinvigorate problem-solving exercises