Hyper-Scaling Relations in the Conformal Window from Dynamic AdS/QCD

Dynamic AdS/QCD is a holographic model of strongly coupled gauge theories with the dynamics included through the running anomalous dimension of the quark bilinear, gamma. We apply it to describe the physics of massive quarks in the conformal window of SU(N_c) gauge theories with N_f fundamental flavours, assuming the perturbative two loop running for gamma. We show that to find regular, holographic, renormalization group flows in the infra-red the decoupling of the quark flavours at the scale of the mass is important and enact it through suitable boundary conditions when the flavours become on shell. We can then compute the quark condensate and the mesonic spectrum (M_rho, M_pi, M_sigma) and decay constants. We compute their scaling dependence on the quark mass for a number of examples. The model matches perturbative expectations for large quark mass and naive dimensional analysis (including the anomalous dimensions) for small quark mass. The model allows study of the intermediate regime where there is an additional scale from the running of the coupling and we present results for the deviation of scalings from assuming only the single scale of the mass.Comment: 12 pages, 26 figures, new references adde

Bowling Boccia on to the map at the University of Lincoln

People who have a disability have traditionally been excluded from different aspects of society like work, education and sports (DePauw and Gavron, 2005: Disability Sports, 15). In recent decades there has been a dramatic change in the extent of this exclusion, as legislation, interventions and programmes have increased the amount of opportunities available to those with a disability (DePauw and Gavron, 2005: Disability Sports, 16). However, even with these changes in recent years the University of Lincoln still provide little sports provision for disability sports and its followers. Therefore the principal aim of this project was to develop and complete a programme evaluation of additional provision of Boccia in the short term, with a view to ensuring long-term provision at the University. The project aimed to increase the awareness of the sport amongst students creating the conditions necessary to start up a club. The project took on a reverse integration approach as reverse integration can serve to promote a better understanding of the actual abilities of people with disability and create an equitable platform for socialisation and competition (Spencer-Cavaliere and Peers, 2011: Adapted Physical Activity Quarterly, 28, 291-309). As Boccia was a new sport to the university, the project focused on the short term goal of increasing the awareness of the sport amongst the university students but also to increase the interest of starting up a club. This was done by organising, promoting and running an event in which the sport was showcased to the students. A programme theory was developed which enabled us to complete a programme evaluation of the project (Evans and Sleap, 2012: International Journal of Aquatic Research and Education, 6, 24-38). A re-aim framework contoured outcome measures of this programme evaluation to ensure the validity and effectiveness of the project. Questionnaires were administered to participants in the programme and results suggested the project met initial targets, including; the increased awareness of Boccia, a number of qualified officials and also an interest in a Boccia specific club at the University. The project highlighted that the students at the University of Lincoln are in need of disability sports provision, beyond Boccia. In conclusion the project was able to increase the awareness of Boccia and this was achieved more so by the reverse integration approach that was taken

Inverse Magnetic Catalysis in Bottom-Up Holographic QCD

We explore the effect of magnetic field on chiral condensation in QCD via a simple bottom up holographic model which inputs QCD dynamics through the running of the anomalous dimension of the quark bilinear. Bottom up holography is a form of effective field theory and we use it to explore the dependence on the coefficients of the two lowest order terms linking the magnetic field and the quark condensate. In the massless theory, we identify a region of parameter space where magnetic catalysis occurs at zero temperature but inverse magnetic catalysis at temperatures of order the thermal phase transition. The model shows similar non-monotonic behaviour in the condensate with B at intermediate T as the lattice data. This behaviour is due to the separation of the meson melting and chiral transitions in the holographic framework. The introduction of quark mass raises the scale of B where inverse catalysis takes over from catalysis until the inverse catalysis lies outside the regime of validity of the effective description leaving just catalysis.Comment: 9 pages, 8 figure

Translational Symmetry Breaking in Higgs & Gauge Theory, and the Cosmological Constant

We argue, at a very basic effective field theory level, that higher dimension operators in scalar theories that break symmetries at scales close to their ultraviolet completion cutoff, include terms that favour the breaking of translation (Lorentz) invariance, potentially resulting in striped, chequered board or general crystal-like phases. Such descriptions can be thought of as the effective low energy description of QCD-like gauge theories near their strong coupling scale where terms involving higher dimension operators are generated. Our low energy theory consists of scalar fields describing operators such as $\bar{q} q$ and $\bar{q} F^{(2n)} q$. Such scalars can have kinetic mixing terms that generate effective momentum dependent contributions to the mass matrix. We show that these can destabilize the translationally invariant vacuum. It is possible that in some real gauge theory such operators could become sufficiently dominant to realize such phases and it would be interesting to look for them in lattice simulations. We present a holographic model of the same phenomena which includes RG running. A key phenomenological motive to look at such states is recent work that shows that the non-linear response in $R^2$ gravity to such short range fluctuations can mimic a cosmological constant. Intriguingly in a cosmology with such a Starobinsky inflation term, to generate the observed value of the present day acceleration would require stripes at the electroweak scale. Unfortunately, low energy phenomenological constraints on Lorentz violation in the electron-photon system appear to strongly rule out any such possibility outside of a disconnected dark sector.Comment: 9 pages, 1 figure; minor changes. Version to be published in PR

Prediction of microgeometrical influences on micropitting fatigue damage on 32CrMoV13 steel

Dr Fabre's sabbatical period at the Cardiff School of Engineering allowed the research to be conducted. Thanks are due to the M2P department of Arts et Métiers ParisTech, to Arts et Métiers ParisTech—Aix en Provence, and to the MécaSurf laboratory for supporting the visit financially, and to Cardiff University for provision of research facilities. Dr Sharif's contribution to the research was supported financially by UK Engineering & Physical Sciences Research Council (EPSRC) with Grant no. EP/G06024X/1.Micropitting is a form of surface fatigue damage that occurs in the gear teeth. It is due to the effect of variation in the mechanical loading in the contact zone between the two teeth, induced especially by flank roughness. In this study, generic roughness profiles were built with geometrical parameters to simulate the contact between two rough surfaces. Using elastohydrodynamic lubrication code and Crossland’s fatigue criteria, the influence on fatigue lifetime was analysed for changes in each parameter. The relevant parameters were determined that influence(i) the conventional pitting,(ii) the extent to which the von Mises equivalent stress exceeds the material yield stress in the zone where micropitting occurs, and(iii) the fatigue lifetime for steel teeth. With nitriding benefits, the same trends were shown with weaker effects

The steady performance of a porous and compliant aerostatic thrust bearing

Recent developments in aerostatic thrust bearings have included: (a) the porous aerostatic thrust bearing containing a porous pad and (b) the inherently compensated compliant surface aerostatic thrust bearing containing a thin elastomer layer. Both these developments have been reported to improve the bearing load capacity compared to conventional aerostatic thrust bearings with rigid surfaces. This development is carried one stage further in a porous and compliant aerostatic thrust bearing incorporating both a porous pad and an opposing compliant surface. The thin elastomer layer forming the compliant surface is bonded to a rigid backing and is of a soft rubber like material. Such a bearing is studied experimentally and theoretically under steady state operating conditions. A mathematical model is presented to predict the bearing performance. In this model is a simplified solution to the elasticity equations for deflections of the compliant surface. Account is also taken of deflections in the porous pad due to the pressure difference across its thickness. The lubrication equations for flow in the porous pad and bearing clearance are solved by numerical finite difference methods. An iteration procedure is used to couple deflections of the compliant surface and porous pad with solutions to the lubrication equations. Comparisons between experimental results and theoretically predicted bearing performance are in good agreement. However these results show that the porous and compliant aerostatic thrust bearing performance is lower than that of a porous aerostatic thrust bearing with a rigid surface in place of the compliant surface. This discovery is accounted to the recess formed in the bearing clearance by deflections of the compliant surface and its effect on flow through the porous pad

The biomechanical role of the chondrocranium and sutures in a lizard cranium

The role of soft tissues in skull biomechanics remains poorly understood. Not least, the chondrocranium, the portion of the braincase which persists as cartilage with varying degrees of mineralization. It also remains commonplace to overlook the biomechanical role of sutures despite evidence that they alter strain distribution. Here, we examine the role of both the sutures and the chondrocranium in the South American tegu lizard Salvator merianae. We use multi-body dynamics analysis (MDA) to provide realistic loading conditions for anterior and posterior unilateral biting and a detailed finite element model to examine strain magnitude and distribution. We find that strains within the chondrocraniumare greatest during anterior biting and are primarily tensile; also that strain within the cranium is not greatly reduced by the presence of the chondrocraniumunless it is given the same material properties as bone. This result contradicts previous suggestions that the anterior portion (the nasal septum) acts as a supporting structure. Inclusion of sutures to the cranium model not only increases overall strain magnitudes but also leads to a more complex distribution of tension and compression rather than that of a beam under sagittal bending