38,420 research outputs found

    Matter Dependence of the Three-Loop Soft Anomalous Dimension Matrix

    Get PDF
    The resummation of soft gluon exchange for QCD hard scattering requires a matrix of anomalous dimensions, which has been computed through two loops. The two-loop matrix is proportional to the one-loop matrix. Recently there have been proposals that this proportionality extends to higher loops. One can test such proposals by computing the dependence of this matrix on the matter content in a generic gauge theory. It is shown that for the matter-dependent part the proportionality extends to three loops for arbitrary massless processes.Comment: 5 pages, 2 figures; v2 minor clarifications, references adde

    The Principle of Maximal Transcendentality and the Four-Loop Collinear Anomalous Dimension

    Full text link
    We use the principle of maximal transcendentality and the universal nature of subleading infrared poles to extract the analytic value of the four-loop collinear anomalous dimension in planar N=4{\cal N}=4 super-Yang-Mills theory from recent QCD results, obtaining G^0(4)=300ζ7256ζ2ζ5384ζ3ζ4\hat{\cal G}_{0}^{(4)} = - 300 \zeta_7 - 256 \zeta_2 \zeta_5 - 384 \zeta_3 \zeta_4. This value agrees with a previous numerical result to within 0.2 percent. It also provides the Regge trajectory, threshold soft anomalous dimension and rapidity anomalous dimension through four loops.Comment: 12 pages, no figures. v2, references adde

    Twistor String Theory and QCD

    Full text link
    I review recent progress in using twistor-inspired methods to compute perturbative scattering amplitudes in gauge theory, for application to collider physics.Comment: 17 pages, 9 figures. Presented at the International Europhysics Conference on High Energy Physics (Lisbon, July, 2005

    Higher Spin BRS Cohomology of Supersymmetric Chiral Matter in D=4

    Full text link
    We examine the BRS cohomology of chiral matter in N=1N=1, D=4D=4 supersymmetry to determine a general form of composite superfield operators which can suffer from supersymmetry anomalies. Composite superfield operators \Y_{(a,b)} are products of the elementary chiral superfields SS and \ov S and the derivative operators D_\a, \ov D_{\dot \b} and \pa_{\a \dot \b}. Such superfields \Y_{(a,b)} can be chosen to have `aa' symmetrized undotted indices \a_i and `bb' symmetrized dotted indices \dot \b_j. The result derived here is that each composite superfield \Y_{(a,b)} is subject to potential supersymmetry anomalies if aba-b is an odd number, which means that \Y_{(a,b)} is a fermionic superfield.Comment: 15 pages, CPT-TAMU-20/9

    Ultraviolet Behavior of N=8 Supergravity

    Full text link
    In these lectures I describe the remarkable ultraviolet behavior of N=8 supergravity, which through four loops is no worse than that of N=4 super-Yang-Mills theory (a finite theory). I also explain the computational tools that allow multi-loop amplitudes to be evaluated in this theory - the KLT relations and the unitarity method - and sketch how ultraviolet divergences are extracted from the amplitudes.Comment: 30 pages, 12 figures; lectures presented at International School of Subnuclear Physics, 47th Course, Erice Sicily, August 29-September 7, 200

    The interpretation of brain natriuretic peptide in critical care patients; will it ever be useful?

    Get PDF
    The measurement of B-type natriuretic peptide (BNP) is recommended for the diagnosis of decompensated heart failure, the prognosis of chronic heart failure is worse if BNP is increased and studies suggest that BNP is useful to guide therapy. A study by Di Somma and colleagues adds to the body of evidence showing that patients with a marked decrease in BNP concentrations during their hospital admission are less likely to be readmitted with a further adverse cardiac event than patients in whom BNP fails to decrease. However, the wider interpretation of BNP concentrations in critically ill patients with other conditions remains uncertain

    Recent Developments in Perturbative QCD

    Full text link
    I review recent progress in perturbative QCD on two fronts: extending next-to-next-to-leading order QCD corrections to a broader range of collider processes, and applying twistor-space methods (and related spinoffs) to computations of multi-parton scattering amplitudes.Comment: 13 pages, 7 figures. Talk presented at 13th International Workshop on Deep Inelastic Scattering (DIS 05), Madison, Wisconsin, April, 200

    DScent Final Report

    Get PDF
    DScent was a joint project between five UK universities combining research theories in the disciplines of computational inference, forensic psychology and expert decision-making in the area of counter-terrorism. This document discusses the work carried out by Leeds Metropolitan University which covers the research, design and development work of an investigator support system in the area of deception using artificial intelligence. For the purposes of data generation along with system and hypothesis testing the project team devised two closed world games, the Cutting Corners Board Game and the Location Based Game. DScentTrail presents the investigator with a ‘scent trail’ of a suspect’s behaviour over time, allowing the investigator to present multiple challenges to a suspect from which they may prove the suspect guilty outright or receive cognitive or emotional clues of deception (Ekman 2002; Ekman & Frank 1993; Ekman & Yuille 1989; Hocking & Leathers 1980; Knapp & Comadena 1979). A scent trail is a collection of ordered, relevant behavioural information over time for a suspect. There are links into a neural network, which attempts to identify deceptive behavioural patterns of individuals. Preliminary work was carried out on a behavioural based AI module which would work separately alongside the neural network, with both identifying deception before integrating their results to update DScentTrail. Unfortunately the data that was necessary to design such a system was not provided and therefore, this section of research only reached its preliminary stages. To date research has shown that there are no specific patterns of deceptive behaviour that are consistent in all people, across all situations (Zuckerman 1981). DScentTrail is a decision support system, incorporating artificial intelligence (AI), which is intended to be used by investigators and attempts to find ways around the problem stated by Zuckerman above
    corecore