Noncommutative families of instantons

We construct $\theta$-deformations of the classical groups SL(2,H) and Sp(2). Coacting on the basic instanton on a noncommutative four-sphere $S^4_\theta$, we construct a noncommutative family of instantons of charge 1. The family is parametrized by the quantum quotient of $SL_\theta(2,H)$ by $Sp_\theta(2)$.Comment: v2: Minor changes; computation of the pairing at the end of Sect. 5.1 improve

Electroweak and QCD corrections to top-pair hadroproduction in association with heavy bosons

We compute the contribution of order $\alpha_S^2\alpha^2$ to the cross section of a top-antitop pair in association with at least one heavy Standard Model boson -- $Z$, $W^\pm$, and Higgs -- by including all effects of QCD, QED, and weak origin and by working in the automated MadGraph5_aMC@NLO framework. This next-to-leading order contribution is then combined with that of order $\alpha_S^3\alpha$, and with the two dominant lowest-order ones, $\alpha_S^2\alpha$ and $\alpha_S\alpha^2$, to obtain phenomenological results relevant to a 8, 13, and 100~TeV $pp$ collider.Comment: 27 pages, 8 figure

Weak corrections to Higgs hadroproduction in association with a top-quark pair

We present the calculation of the next-to-leading contribution of order $\alpha_S^2\alpha^2$ to the production of a Standard Model Higgs boson in association with a top-quark pair at hadron colliders. All effects of weak and QCD origin are included, whereas those of QED origin are ignored. We work in the MadGraph5_aMC@NLO framework, and discuss sample phenomenological applications at a 8, 13, and 100 TeV $pp$ collider, including the effects of the dominant next-to-leading QCD corrections of order $\alpha_S^3\alpha$.Comment: 29 pages, 38 figure

Chronic fatigue syndrome: A hypothesis focusing on the autonomic nervous system

Chronic fatigue syndrome is a debilitating illness of unknown aetiology, with estimated levels of prevalence of up to about 8.7/100,000 in the U.S.A. Like pain fatigue it is a personal, emotionally rich experience, which may originate from peripheral or central sites (or both). The nature of the symptoms is complex and reflects the interaction of the patient with the environment and cultural milieu. Accordingly the common use of the same terminology for different types of fatigue may be misleading. Autonomic activation is a key component of both real and simulated physical exercise. Alterations in autonomic nervous system activity are a key component of several physiopathological conditions. In chronic fatigue syndrome disturbances in autonomic activity, and in other homoeostatic mechanisms, such as the hormonal and immune systems, have been reported recently. In this review we followed the hypothesis that in chronic fatigue syndrome the paradoxical condition of disturbing somatic symptoms in the absence of organic evidence of disease might be addressed by focusing on attending functional correlates. In particular we addressed possible alterations in cardiovascular autonomic control, as can be assessed by spectral analysis of R-R interval and systolic arterial pressure variability. With this approach, in subjects complaining of unexplained fatigue, we obtained data suggesting a condition of prevailing sympathetic modulation of the sino-atrial node at rest, and reduced responsiveness to excitatory stimuli. Far from considering the issue resolved, we propose that in the context of the multiple physiological and psychological interactions involved in the perception and self-reporting of symptoms, attendant changes in physiological equivalents might furnish a convenient assessment independent from subjective components. Indices of sympathetic modulation could, accordingly, provide quantifiable signs of the interaction between subject's efforts and environmental demands, independently of self descriptions, which could provide convenient measurable outcomes, both for diagnosis and treatment titration in chronic fatigue syndrome

The orbifold cohomology of moduli of genus 3 curves

In this work we study the additive orbifold cohomology of the moduli stack of smooth genus g curves. We show that this problem reduces to investigating the rational cohomology of moduli spaces of cyclic covers of curves where the genus of the covering curve is g. Then we work out the case of genus g=3. Furthermore, we determine the part of the orbifold cohomology of the Deligne-Mumford compactification of the moduli space of genus 3 curves that comes from the Zariski closure of the inertia stack of M_3.Comment: 29 pages, 2 figures. Minor changes, to appear in Manuscripta Mat

The automation of next-to-leading order electroweak calculations

We present the key features relevant to the automated computation of all the leading- and next-to-leading order contributions to short-distance cross sections in a mixed-coupling expansion, with special emphasis on the first subleading NLO term in the QCD+EW scenario, commonly referred to as NLO EW corrections. We discuss, in particular, the FKS subtraction in the context of a mixed-coupling expansion; the extension of the FKS subtraction to processes that include final-state tagged particles, defined by means of fragmentation functions; and some properties of the complex mass scheme. We combine the present paper with the release of a new version of MadGraph5_aMC@NLO, capable of dealing with mixed-coupling expansions. We use the code to obtain illustrative inclusive and differential results for the 13-TeV LHC.Comment: 121 pages, 16 figure

Chemistry and kinematics of the pre-stellar core L1544: Constraints from H2D+

This paper explores the sensitivity of line profiles of H2D+, HCO+ and N2H+, observed towards the center of L1544, to various kinematic and chemical parameters. The total width of the H2D+ line can be matched by a static model and by models invoking ambipolar diffusion and gravitational collapse. The derived turbulent line width is b=0.15 km/s for the static case and <~ 0.05 km/s for the collapse case. However, line profiles of HC18O+ and N2H+ rule out the static solution. The double-peaked H2D+ line shape requires either infall speeds in the center that are much higher than predicted by ambipolar diffusion models, or a shell-type distribution of H2D+, as is the case for HCO+ and N2H+. At an offset of ~20 arcsec from the dust peak, the H2D+ abundance drops by a factor of ~5.Comment: four pages, two colour figures; to appear in The Dense Interstellar Medium in Galaxies, proceedings of the fourth Cologne-Bonn-Zermatt Symposium, Sept 22-26, 200

A study on various methods of supplying propellant to an orbit insertion rocket engine

Various types of pumps and pump drives were evaluated to determine the lightest weight system for supplying propellants to a planetary orbit insertion rocket engine. From these analyses four candidate propellant feed systems were identified. Systems Nos. 1 and 2 were both battery powered (lithium-thionyl-chloride or silver-zinc) motor driven pumps. System 3 was a monopropellant gas generator powered turbopump. System 4 was a bipropellant gas generator powered turbopump. Parameters considered were pump break horsepower, weight, reliability, transient response and system stability. Figures of merit were established and the ranking of the candidate systems was determined. Conceptual designs were prepared for typical motor driven pumps and turbopump configurations for a 1000 lbf thrust rocket engine