2,739 research outputs found
A Superfield for Every Dash-Chromotopology
The recent classification scheme of so-called adinkraic off-shell
supermultiplets of N-extended worldline supersymmetry without central charges
finds a combinatorial explosion. Completing our earlier efforts, we now
complete the constructive proof that all of these trillions or more of
supermultiplets have a superfield representation. While different as
superfields and supermultiplets, these are still super-differentially related
to a much more modest number of minimal supermultiplets, which we construct
herein.Comment: 13 pages, integrated illustration
Effective Symmetries of the Minimal Supermultiplet of N = 8 Extended Worldline Supersymmetry
A minimal representation of the N = 8 extended worldline supersymmetry, known
as the `ultra-multiplet', is closely related to a family of supermultiplets
with the same, E(8) chromotopology. We catalogue their effective symmetries and
find a Spin(4) x Z(2) subgroup common to them all, which explains the
particular basis used in the original construction. We specify a constrained
superfield representation of the supermultiplets in the ultra-multiplet family,
and show that such a superfield representation in fact exists for all adinkraic
supermultiplets. We also exhibit the correspondences between these
supermultiplets, their Adinkras and the E(8) root lattice bases. Finally, we
construct quadratic Lagrangians that provide the standard kinetic terms and
afford a mixing of an even number of such supermultiplets controlled by a
coupling to an external 2-form of fluxes.Comment: 13 Figure
Early Dark Energy Cosmologies
We propose a novel parameterization of the dark energy density. It is
particularly well suited to describe a non-negligible contribution of dark
energy at early times and contains only three parameters, which are all
physically meaningful: the fractional dark energy density today, the equation
of state today and the fractional dark energy density at early times. As we
parameterize Omega_d(a) directly instead of the equation of state, we can give
analytic expressions for the Hubble parameter, the conformal horizon today and
at last scattering, the sound horizon at last scattering, the acoustic scale as
well as the luminosity distance. For an equation of state today w_0 < -1, our
model crosses the cosmological constant boundary. We perform numerical studies
to constrain the parameters of our model by using Cosmic Microwave Background,
Large Scale Structure and Supernovae Ia data. At 95% confidence, we find that
the fractional dark energy density at early times Omega_early < 0.06. This
bound tightens considerably to Omega_early < 0.04 when the latest Boomerang
data is included. We find that both the gold sample of Riess et. al. and the
SNLS data by Astier et. al. when combined with CMB and LSS data mildly prefer
w_0 < -1, but are well compatible with a cosmological constant.Comment: 6 pages, 3 figures; references added, matches published versio
How to identify when a performance indicator has run its course
The official published version can be found at the link below.Increasing numbers of countries are using indicators to evaluate the quality of clinical care, with some linking payment to achievement. For performance frameworks to remain effective the indicators need to be regularly reviewed. The frameworks cannot cover all clinical areas, and achievement on chosen indicators will eventually reach a ceiling beyond which further improvement is not feasible. However, there has been little work on how to select indictors for replacement. The Department of Health decided in 2008 that it would regularly replace indicators in the national primary care pay for performance scheme, the Quality and Outcomes Framework, making a rigorous approach to removal a priority. We draw on our previous work on pay for performance and our current work advising the National Institute for Health and Clinical Excellence (NICE) on the Quality and Outcomes Framework to suggest what should be considered when planning to remove indicators from a clinical performance framework
Orbifold Models in M-Theory
Among orbifold compactifications of -theory, we examine
models containing the particle physics Standard Model in four-dimensional
spacetimes, which appear as fixed subspaces of the ten-dimensional spacetimes
at each end of the interval, , spanning the
dimension. Using the projection to break the gauge symmetry in each
of the four-planes and a limiting relation to corresponding heterotic string
compactifications, we discuss the restrictions on the possible resulting gauge
field and matter spectra. In particular, some of the states are non-local: they
connect two four-dimensional Worlds across the dimension.
We illustrate our programmable calculations of the matter field spectrum,
including the anomalous U(1) factor which satisfies a universal Green-Schwarz
relation, discuss a Dynkin diagram technique to showcase a model with
gauge symmetry, and discuss generalizations to
higher order orbifolds.Comment: 23 pages, 2 figures, 4 tables; LaTeX 3 time
A genomic approach to understanding the cause and effect of annual ryegrass toxicity
Annual Ryegrass Toxicity (ARGT) is a potentially lethal disease affecting livestock grazing on pastures or consuming fodder that include annual ryegrass (Lolium rigidum) contaminated with corynetoxins. The corynetoxins (CTs), among the most lethal toxins produced in nature, are produced by the bacterium Rathayibacter toxicus that uses a nematode vector to attach to and infect the seedheads of L.rigidum. There is little known of the factors that control toxin production. Several studies have speculated that a bacteriophage specific to R.toxicus may be implicated in CT production. We have developed a PCR-based assay to test for both bacterium and phage in ryegrass material and results indicate that there is a correlation between phage and bacterial presence in all toxic ryegrass samples tested so far. This PCR-based technique may ultimately allow for a rapid, high-throughput screening assay to identify potentially toxic pastures and feed in the field. Currently, ~80% of the 45 Kb genome has been sequenced an investigation to further elucidate its potential role in toxin production.Furthermore, specific alterations in gene expression as a result of exposure to CTs or the closely related tunicamycins (TMs), which are commercially available and considered biologically indistinguishable from CTs, will be evaluated for use as biomarkers of exposure. The effects of both toxins will be analysed in vitro using a rat hepatocyte cell line and screened on a low-density DNA micro array “CT-Chip” that contains <100 selected rat hepatic genes. The results are expected to further define the bioequivalence of CTs and TMs and to identify levels of exposure that are related to specific toxic effects or have no adverse effect on livestock.<br /
New Techniques for Analysing Axisymmetric Gravitational Systems. 1. Vacuum Fields
A new framework for analysing the gravitational fields in a stationary,
axisymmetric configuration is introduced. The method is used to construct a
complete set of field equations for the vacuum region outside a rotating
source. These equations are under-determined. Restricting the Weyl tensor to
type D produces a set of equations which can be solved, and a range of new
techniques are introduced to simplify the problem. Imposing the further
condition that the solution is asymptotically flat yields the Kerr solution
uniquely. The implications of this result for the no-hair theorem are
discussed. The techniques developed here have many other applications, which
are described in the conclusions.Comment: 30 pages, no figure
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