External leg amputation in conformal invariant three-point function

Amputation of external legs is carried out explicitly for the conformal invariant three-point function involving two spinors and one vector field. Our results are consistent with the general result that amputing an external leg in a conformal invariant Green function replaces a field by its conformal partner in the Green function. A new star-triangle relation, involving two spinors and one vector field, is derived and used for the calculation.Comment: 16 pages; last paragraph added in Sec. 10, presentation improved, to appear in Eur. Phys. J.

Three-point Green function of massless QED in position space to lowest order

The transverse part of the three-point Green function of massless QED is determined to the lowest order in position space. Taken together with the evaluation of the longitudinal part in arXiv:0803.2630, this gives a relation for QED which is analogous to the star-triangle relation. We relate our result to conformal-invariant three-point functions.Comment: 8 page

Development of an instrument for non-destructive identification of Unexploded Ordnance using tagged neutrons - a proof of concept study

Range clearance operations at munitions testing grounds must discriminate Unexploded Ordnance (UXO) from clutter items and distinguish UXO filled with High Explosives (HE) from those with inert fillers. Non-destructive technologies are thus necessary for the cost-effective disposal of UXO during remediation of such sites. The only technique showing promise so far for the non-destructive elemental characterization of UXO fillers utilizes neutron interactions with the material to detect carbon (C), nitrogen (N) and oxygen (O) which have unique ratios in HE. However, several unresolved issues hinder the wide application of this potentially very suitable technique. The most important one is that neutrons interact with all surrounding matter in addition to the interrogated material, leading to a very high gamma-ray background in the detector. Systems requiring bulky shielding and having poor signal-to-noise ratios (SNRs) for measuring elements are unsuitable for field deployment. The inadequacies of conventional neutron interrogation methods are overcome by using the tagged-neutron approach, and the availability of compact sealed neutron generators exploiting this technique offers field deployment of non-intrusive measurement systems for detecting threat materials, like explosives and drugs. By accelerating deuterium ions into a tritium target, the subsequent fusion reaction generates nearly back-to-back emissions of neutrons and alpha particles of energy 14.1 and 3.5 MeV respectively. A position-sensitive detector recognizes the associated alpha particle, thus furnishing the direction of the neutron. The tagged neutrons interact with the nuclei of the interrogated object, producing element-specific prompt gamma-rays that the gamma detectors recognize. Measuring the delay between the detections of the alpha particle and the gamma-ray determines where the reaction occurred along the axis of the neutron beam (14.1 MeV neutrons travel at 5 cm/nanosecond, while gamma rays cover 30 cm/nanosecond). The main advantage of the technique is its ability to simultaneously provide 2D and 3D imaging of objects and their elemental composition. This work reports on the efficacy of using 14 MeV neutrons tagged by the associated particle neutron time-of-flight technique (APnTOF) to extract neutron induced characteristic gamma-rays from an object-of-interest with high SNR and without interference from nearby clutter

Evidence for a Finite Temperature Insulator

In superconductors the zero-resistance current-flow is protected from dissipation at finite temperatures (T) by virtue of the short-circuit condition maintained by the electrons that remain in the condensed state. The recently suggested finite-T insulator and the "superinsulating" phase are different because any residual mechanism of conduction will eventually become dominant as the finite-T insulator sets-in. If the residual conduction is small it may be possible to observe the transition to these intriguing states. We show that the conductivity of the high magnetic-field insulator terminating superconductivity in amorphous indium-oxide exhibits an abrupt drop, and seem to approach a zero conductance at T<0.04 K. We discuss our results in the light of theories that lead to a finite-T insulator

A refined Razumov-Stroganov conjecture

We extend the Razumov-Stroganov conjecture relating the groundstate of the O(1) spin chain to alternating sign matrices, by relating the groundstate of the monodromy matrix of the O(1) model to the so-called refined alternating sign matrices, i.e. with prescribed configuration of their first row, as well as to refined fully-packed loop configurations on a square grid, keeping track both of the loop connectivity and of the configuration of their top row. We also conjecture a direct relation between this groundstate and refined totally symmetric self-complementary plane partitions, namely, in their formulation as sets of non-intersecting lattice paths, with prescribed last steps of all paths.Comment: 20 pages, 4 figures, uses epsf and harvmac macros a few typos correcte

Criterion for dynamical chiral symmetry breaking

The Bethe-Salpeter equation is related to a generalized quantum-mechanical Hamiltonian. Instability of the presumed vacuum, indicated by a tachyon, is related to a negative energy eigenstate of this Hamiltonian. The variational method shows that an arbitrarily weak long-range attraction leads to chiral symmetry breaking, except in the scale-invariant case when the instability occurs at a critical value of the coupling. In the case of short-range attraction, an upper bound for the critical coupling is obtained.Comment: 10 pages, 2 figures; made minor changes, published versio

Perceptions and experiences of financial incentives: a qualitative study of dialysis care in England

OBJECTIVE: The objective of the study was to understand the extent to which financial incentives such as Payment by Results and other payment mechanisms motivate kidney centres in England to change their practices. DESIGN: The study followed a qualitative design. Data collection involved 32 in-depth semistructured interviews with healthcare professionals and managers, focusing on their subjective experience of payment structures. PARTICIPANTS: Participants were kidney healthcare professionals, clinical directors, kidney centre managers and finance managers. Healthcare commissioners from different parts of England were also interviewed. SETTING: Participants worked at five kidney centres from across England. The selection was based on the prevalence of home haemodialysis, ranging from low (<3%), medium (5–8%) and high (>8%) prevalence, with at least one centre in each one of these categories at the time of selection. RESULTS: While the tariff for home haemodialysis is not a clear incentive for its adoption due to uncertainty about operational costs, Commissioning for Quality and Innovation (CQUIN) targets and the Best Practice Tariff for vascular access were seen by our case study centres as a motivator to change practices. CONCLUSIONS: The impact of financial incentives designed at a policy level is influenced by the understanding of cost and benefits at the local operational level. In a situation where costs are unclear, incentives which are based on the improvement of profit margins have a smaller impact than incentives which provide an additional direct payment, even if this extra financial support is relatively small

Evolution of dynamical motions in monolayer protected metal-clusters

Here we report orientational dynamics in monolayer protected metal-cluster (MPC) systems as studied by quasielastic neutron scattering (QENS) technique. Experiments carried out using two different instruments having very different energy windows, thus covering a time scale of 10-9-10-12 s. Clear evidence of absence of 'rotator phase' has been found in isolated MPCs (Au-SC18H37, Au-SC12H25, Au-SC8H17 and Au-SC6H13), a superlattice MPC (Ag-SC18H37) as well as planar thiolates (Ag-SC6H13, Ag-SC12H25, Ag-SC18H37) at room temperature. However, dynamics were found to evolve on increase of temperature and its behaviour is found to be different in the superlattice and isolated cluster systems. Detailed dynamical informations for MPCs are obtained for the first time in these systems