A note on the third family of N=2 supersymmetric KdV hierarchies

We propose a hamiltonian formulation of the $N=2$ supersymmetric KP type hierarchy recently studied by Krivonos and Sorin. We obtain a quadratic hamiltonian structure which allows for several reductions of the KP type hierarchy. In particular, the third family of $N=2$ KdV hierarchies is recovered. We also give an easy construction of Wronskian solutions of the KP and KdV type equations

Effective field theories for QED bound states: extending Nonrelativistic QED to study retardation effects

Nonrelativistic QED bound states are difficult to study because of the presence of at least three widely different scales: the masses, three-momenta ($p_i$) and kinetic energies ($K_i$) of the constituents. Nonrelativistic QED (NRQED), an effective field theory developed by Caswell and Lepage, simplifies greatly bound state calculations by eliminating the masses as dynamical scales. As we demonstrate, NRQED diagrams involving only photons of energy $E_\gamma \simeq p_i$ contribute, in any calculation, to a unique order in $\alpha$. This is not the case, however, for diagrams involving photons with energies $E_\gamma \simeq K_i$ (``retardation effects"), for which no simple counting counting rules can be given. We present a new effective field theory in which the contribution of those ultra-soft photons can be isolated order by order in $\alpha$. This is effectively accomplished by performing a multipole expansion of the NRQED vertices.Comment: 39 pages, 9 Postscript figures, uses Rev.tex V3.0 and epsf.te

Relativistic and Binding Energy Corrections to Direct Photon Production In Upsilon Decay

A systematic gauge-invariant method is used to calculate the rate for an upsilon meson to decay inclusively into a prompt photon. An expansion is made in the quark relative velocity v, which is a small natural parameter for heavy quark systems. Inclusion of these O(v^2) corrections tends to increase the photon rate in the middle z range and to lower it for larger z, a feature supported by the data.Comment: 13 pages, LateX, One figure (to be published in Phys. Rev. D, Sept. 1, 1996

Telemetry-validated nitrogen stable isotope clocks identify ocean-to-estuarine habitat shifts in mobile organisms

Throughout their life history, many animals transition among heterogeneous environments to facilitate behaviours such as reproduction, foraging and predator avoidance. The dynamic environmental and biological conditions experienced by mobile species are integrated in the chemical composition of their tissues, providing retrospective insight into movement. Here, we present a unique application of nitrogen stable isotope clocks (‘isotopic clocks’), which integrate tissue turnover rates, consumer stable isotope ratios and habitat-specific isotope baselines to predict time-since-immigration and the timing of habitat shifts in a migratory species. Nitrogen stable isotope values of blood plasma collected from juvenile sand tiger sharks Carcharias taurus, a species known to undertake seasonal movements between ocean and estuarine environments, were used to derive estimates of time-since-immigration and the timing of seasonal habitat shifts undertaken by this species. Nitrogen isotopic clocks estimated for 65 juvenile sand tiger sharks sampled across 6 years indicated that individual sharks predominantly arrived to estuarine habitats between June and July, with some individuals arriving as early as mid-May. These estimates were validated by comparing isotope-derived estuarine arrival times with those from acoustically tracked individuals. The median estuarine arrival day estimates from our isotopic approach aligned with estimates from acoustic telemetry for each sampling population. Sensitivity analyses indicated that isotopically inferred time-since-immigration and estuarine arrival estimates were robust to variation in isotopic turnover rate and diet tissue discrimination factors under multiple modelling scenarios. This suggests that parameterization of the nitrogen isotopic clock provides reliable estimates of time-since-immigration and day of arrival into new habitats if isotopic variation exists between origin and new locations. Our study presents a unique application of telemetry-validated isotope clocks to derive retrospective estimates of time-since-immigration and timing of habitat shifts for animals that seasonally traverse heterogeneous environments. This approach can be readily applied across many temporal and spatial scales, and to other species and ecosystems, to facilitate rapid assessment of changes in animal habitat use and broader ecosystem structure

Soft-Collinear Factorization in Effective Field Theory

The factorization of soft and ultrasoft gluons from collinear particles is shown at the level of operators in an effective field theory. Exclusive hadronic factorization and inclusive partonic factorization follow as special cases. The leading order Lagrangian is derived using power counting and gauge invariance in the effective theory. Several species of gluons are required, and softer gluons appear as background fields to gluons with harder momenta. Two examples are given: the factorization of soft gluons in B->D pi, and the soft-collinear convolution for the B->Xs gamma spectrum.Comment: 32 pages, 11 figs, journal versio

The QCD Potential at O(1/m)O(1/m)

Within an effective field theory framework, we obtain an expression for the next-to-leading term in the $1/m$ expansion of the singlet $Q{\bar Q}$ QCD potential in terms of Wilson loops, which holds beyond perturbation theory. The ambiguities in the definition of the QCD potential beyond leading order in $1/m$ are discussed and a specific expression for the $1/m$ potential is given. We explicitly evaluate this expression at one loop and compare the outcome with the existing perturbative results. On general grounds we show that for quenched QED and fully Abelian-like models this expression exactly vanishes.Comment: 19 pages, LaTeX, 1 figure. Journal version. Discussion refined, misprints corrected, few references added; results unchange

Colour-Octet Effects in Radiative Υ\Upsilon Decays

We investigate the effects of colour-octet contributions to the radiative $\Upsilon$ decay within the Bodwin, Braaten and Lepage NRQCD factorization framework. Photons coming both from the coupling to hard processes (`direct') and by collinear emission from light quarks (`fragmentation') are consistently included at next-to-leading order (NLO) in $\alpha_s$. An estimate for the non-perturbative matrix elements which enter in the final result is then obtained. By comparing the NRQCD prediction at NLO for total decay rates with the experimental data, it is found that the non-perturbative parameters must be smaller than expected from the na\"\i ve scaling rules of NRQCD. Nevertheless, colour-octet contributions to the shape of the photon spectrum turn out to be significant.Comment: 25 pages, Latex, 8 figure

Eight-component two-fermion equations

An eight-component formalism is proposed for the relativistic two-fermion problem. In QED, it extends the applicability of the Dirac equation with hyperfine interaction to the positronium case. The use of exact relativistic two-body kinematics entails a CP-invariant spectrum which is symmetric in the total cms energy. It allows the extension of recent \alpha^6 recoil corrections to the positronium case, and implies new recoil corrections to the fine and hyperfine structures and to the Bethe logarithm.Comment: Revtex, accepted for publication in Phys. Rev.

Retreat into scientism, paradoxes of transparency, and corruption in education

Um dos sintomas da razão indolente (SANTOS, 2006) é o recuo ao cientificismo, o qual tem sido, particularmente, acentuado nas políticas, cada vez mais hegemônicas, de avaliação, de prestação de contas e de responsabilização. Por isso, um dos objetivos deste texto é o de colocar em causa este aparente consenso cientificista (ou este consenso supostamente transideológico) e fazer uma breve incursão exploratória ao que aqui se designa de paradoxos da transparência. Considera-se que esses paradoxos traduzem a existência de tensões e contradições relativas a uma dimensão central dos discursos políticos e educacionais contemporâneos. Com isso, o artigo pretende dar continuidade a uma linha de pesquisa que tem procurado sublinhar a relevância da necessidade de complexificar e dar maior rigor teórico-conceptual à accountability em educação. Finalmente, tentando abrir caminho para o desenvolvimento de novas articulações e análises, chama-se a atenção para a corrupção na educação cuja complexidade ainda é insuficientemente conhecida e pesquisada, nomeadamente, nas suas relações com as problemáticas da transparência e da accountability. Admite-se que as práticas de corrupção em educação, em muitas situações, são (paradoxalmente) induzidas pela necessidade de dar resposta à governação baseada nos números, nos rankings e nas (supostas) evidências, anulando completamente as expectativas legítimas em torno da transparência dos processos educacionais e das decisões políticas.One symptom of “indolent reason” (SANTOS, 2006) is the retreat into scientism, which is especially marked in the increasingly hegemonic policies surrounding assessment, reporting and accountability. As such, one of the aims of this paper is to call into question this apparent consensus on scientism (a supposedly trans-ideological consensus), and briefly explore what we define as the paradoxes of transparency. These paradoxes are found to reveal the existence of tensions and contradictions concerning a central aspect of current political and educational discourse. In doing so, the article seeks to continue a line of study which has aimed to emphasize the significance of the need for a more complex, and theoretically and conceptually rigorous understanding of accountability in education. Finally, in an attempt to pave the way for further discussion and analysis, attention is drawn to corruption in education, the complex nature of which remains insufficiently understood and studied, notably in terms of its relationship with the problems of transparency and accountability. It is acknowledged that practices of corruption within education are, in many situations, (paradoxically) caused by the need to answer to a system of governance based on numbers, league tables, and (supposed) truths, completely nullifying legitimate expectations about the transparency of educational processes and policy decisions.Trabalho financiado por Fundos Nacionais através da FCT – Fundação para a Ciência e a Tecnologia – no âmbito do Projeto PEst-OE/CED/UI1661/2014.info:eu-repo/semantics/publishedVersio