Baryon Resonance Analysis from SAID

We discuss the analysis of data from piN elastic scattering and single pion photo- and electroproduction. The main focus is a study of low-lying non-strange baryon resonances. Here we concentrate on some difficulties associated with resonance identification, in particular the Roper and higher P11 states.Comment: 4 pages, 6 figures; Nstar2009 Conf Proceedings; small revisio

The homotopy theory of dg-categories and derived Morita theory

The main purpose of this work is the study of the homotopy theory of dg-categories up to quasi-equivalences. Our main result provides a natural description of the mapping spaces between two dg-categories $C$ and $D$ in terms of the nerve of a certain category of $(C,D)$-bimodules. We also prove that the homotopy category $Ho(dg-Cat)$ is cartesian closed (i.e. possesses internal Hom's relative to the tensor product). We use these two results in order to prove a derived version of Morita theory, describing the morphisms between dg-categories of modules over two dg-categories $C$ and $D$ as the dg-category of $(C,D)$-bi-modules. Finally, we give three applications of our results. The first one expresses Hochschild cohomology as endomorphisms of the identity functor, as well as higher homotopy groups of the \emph{classifying space of dg-categories} (i.e. the nerve of the category of dg-categories and quasi-equivalences between them). The second application is the existence of a good theory of localization for dg-categories, defined in terms of a natural universal property. Our last application states that the dg-category of (continuous) morphisms between the dg-categories of quasi-coherent (resp. perfect) complexes on two schemes (resp. smooth and proper schemes) is quasi-equivalent to the dg-category of quasi-coherent complexes (resp. perfect) on their product.Comment: 50 pages. Few mistakes corrected, and some references added. Thm. 8.15 is new. Minor corrections. Final version, to appear in Inventione

Topological complexity of the relative closure of a semi-Pfaffian couple

Gabrielov introduced the notion of relative closure of a Pfaffian couple as an alternative construction of the o-minimal structure generated by Khovanskii's Pfaffian functions. In this paper, use the notion of format (or complexity) of a Pfaffian couple to derive explicit upper-bounds for the homology of its relative closure. Keywords: Pfaffian functions, fewnomials, o-minimal structures, Betti numbers.Comment: 12 pages, 1 figure. v3: Proofs and bounds have been slightly improve

The Effect of Humidity on the Reliability of a Surface Micromachined Microengine

Humidity is shown to be a strong factor in the wear of rubbing surfaces in polysilicon micromachines. We demonstrate that very low humidity can lead to very high wear without a significant change in reliability. We show that the volume of wear debris generated is a function of the humidity in an air environment. As the humidity decreases, the wear debris generated increases. For the higher humidity levels, the formation of surface hydroxides may act as a lubricant. The dominant failure mechanism has been identified as wear. The wear debris has been identified as amorphous oxidized silicon. Large slivers (approximately 1 micron in length) of debris observed at the low humidity level were also amorphous oxidized silicon. Using transmission electron microscopy, we observed that the wear debris forms spherical and rod-like shapes. We compared two surface treatment processes: a fluorinated si- lane chain, (FITl) and supercritical C02 dried (SCC02). The microengines using the SCC02 process were found to be less reliable than those released with the FIX process under two humidity levels

Distributive justice with and without culture

Academic treatments of distributive justice normally adopt a static approach centred on resource allocation among a set of individual agents. The resulting models, expressed in mathematical language, make no allowance for culture, as they never engage with the society’s way of life or the moulding of individuals within society. This paper compares the static approach to distributive justice with a cultural one, arguing that a case for redistribution should rest upon its cultural effects in assisting well-being and social cohesion. Unless we recognise culture, we can have little understanding of why inequalities matter, where they come from, and how they might be reduced. Redistribution may be motivated by universal value judgements taken from external sources, but it also entails internal cultural changes that refashion social relations through cumulative causation. In practical terms, it has to penetrate beyond reallocating resource endowments to bring revised attitudes in a society less tolerant of unequal outcomes. Egalitarian reforms will flourish only if they generate and reflect an egalitarian culture

Photoproduction of pions and properties of baryon resonances from a Bonn-Gatchina partial wave analysis

Masses, widths and photocouplings of baryon resonances are determined in a coupled-channel partial wave analysis of a large variety of data. The Bonn-Gatchina partial wave formalism is extended to include a decomposition of t- and u-exchange amplitudes into individual partial waves. The multipole transition amplitudes for $\gamma p\to p\pi^0$ and $\gamma p\to n\pi^+$ are given and compared to results from other analyses.Comment: 18 pages, 14 figure

Measurement of the beam asymmetry Sigma for pi(0) and eta photoproduction on the proton at E-gamma=9 GeV

We report measurements of the photon beam asymmetry Sigma for the reactions (gamma) over right arrowp -\u3e p pi(0) and gamma p -\u3e p eta from the GLUEX experiment using a 9 GeV linearly polarized, tagged photon beam incident on a liquid hydrogen target in Jefferson Lab\u27s Hall D. The asymmetries, measured as a function of the proton momentum transfer, possess greater precision than previous pi(0) measurements and are the first. measurements in this energy regime. The results are compared with theoretical predictions based on t-channel, quasiparticle exchange and constrain the axial-vector component of the neutral meson production mechanism in these models