UK Business Investment: Long-Run Elasticities and Short-Run Dynamics

From neoclassical theory output, capital stock and the user cost are cointegrated; capital and investment also (multi)cointegrate through the capital accumulation identity. An investment equation is estimated on UK data using a new capital stock series and a long series for the weighted cost of capital. Assuming CES technology, the elasticity of substitution is well-determined and below unity. Over-identifying restrictions are accepted. The long-run parameter is robust to alternative specifications, but single-equation investment relationships may obscure the dynamics. The Johansen method is over-sized, but outperforms a single equation test for excluding the capital accumulation identity from the investment equation.investment, capital stock, identification, multicointegration

Persistent homology of groups

We introduce and investigate notions of persistent homology for p-groups and for coclass trees of p-groups. Using computer techniques we show that persistent homology provides fairly strong homological invariants for p-groups of order at most 81. The strength of these invariants, and some elementary theoretical properties, suggest that persistent homology may be a useful tool in the study of prime-power groups.Comment: 12 pages, 6 figure

Attitudes and principles of making

This is a list of principles – or perhaps attitudes – of choreographic practice and making. The list is not exhaustive, and indeed comprises many ideas that are so general that they would hold for any kind of making. In such a way they demand that we consider to what extent choreographic making is special at all. Perhaps the list might – as we continue to consider the nature of choreographic practices – help to provoke our questions, our processes, our methods and our choreographies

PRAXIS: a low background NIR spectrograph for fibre Bragg grating OH suppression

Fibre Bragg grating (FBG) OH suppression is capable of greatly reducing the bright sky background seen by near infrared spectrographs. By filtering out the airglow emission lines at high resolution before the light enters the spectrograph this technique prevents scattering from the emission lines into interline regions, thereby reducing the background at all wavelengths. In order to take full advantage of this sky background reduction the spectrograph must have very low instrumental backgrounds so that it remains sky noise limited. Both simulations and real world experience with the prototype GNOSIS system show that existing spectrographs, designed for higher sky background levels, will be unable to fully exploit the sky background reduction. We therefore propose PRAXIS, a spectrograph optimised specifically for this purpose. The PRAXIS concept is a fibre fed, fully cryogenic, fixed format spectrograph for the J and H-bands. Dark current will be minimised by using the best of the latest generation of NIR detectors while thermal backgrounds will be reduced by the use of a cryogenic fibre slit. Optimised spectral formats and the use of high throughput volume phase holographic gratings will further enhance sensitivity. Our proposal is for a modular system, incorporating exchangeable fore-optics units, integral field units and OH suppression units, to allow PRAXIS to operate as a visitor instrument on any large telescope and enable new developments in FBG OH suppression to be incorporated as they become available. As a high performance fibre fed spectrograph PRAXIS could also serve as a testbed for other astrophotonic technologies.Comment: 7 pages, 3 figures, published in Proc. SPIE 845

Astrophysical signatures of leptonium

More than 10^43 positrons annihilate every second in the centre of our Galaxy yet, despite four decades of observations, their origin is still unknown. Many candidates have been proposed, such as supernovae and low mass X-ray binaries. However, these models are difficult to reconcile with the distribution of positrons, which are highly concentrated in the Galactic bulge, and therefore require specific propagation of the positrons through the interstellar medium. Alternative sources include dark matter decay, or the supermassive black hole, both of which would have a naturally high bulge-to-disc ratio. The chief difficulty in reconciling models with the observations is the intrinsically poor angular resolution of gamma-ray observations, which cannot resolve point sources. Essentially all of the positrons annihilate via the formation of positronium. This gives rise to the possibility of observing recombination lines of positronium emitted before the atom annihilates. These emission lines would be in the UV and the NIR, giving an increase in angular resolution of a factor of 10^4 compared to gamma ray observations, and allowing the discrimination between point sources and truly diffuse emission. Analogously to the formation of positronium, it is possible to form atoms of true muonium and true tauonium. Since muons and tauons are intrinsically unstable, the formation of such leptonium atoms will be localised to their places of origin. Thus observations of true muonium or true tauonium can provide another way to distinguish between truly diffuse sources such as dark matter decay, and an unresolved distribution of point sources.Comment: Accepted for publication in EPJ-D, 9 pages, 4 figure

Screendance Now

Editorial for IJSD volume 10

IJSD Volume 6 Editorial: Field Perceptions

No abstract available

Unexamined Assumptions: A Conversation between Arabella Stanger and Simon Ellis

A Conversation between Arabella Stanger and Simon Ellis regarding student screendance projects at Roehampton University