1,113 research outputs found
Off shell -symmetry of the superparticle and the spinning superparticle
The spinorial local world-line -symmetry of the covariant
Brink-Schwarz formulation of the 4- superparticle is abelian in an off-shell
phase-space formulation. The result is shown to generalize to the extended
spinorial transformations of the spinning superparticle.Comment: 9 pages, no fig
Congruence and scope for incorporating ACTIVE principles into project management competency frameworks
Project Management competency has been recognised as a critical source of competitive
advantage and key to successful project delivery. For this reason it is important that the
competency frameworks used to achieve competence in project organizations are effective
and fit for purpose. The European Construction Institute (ECI) developed eight principles
through the ACTIVE (Achieving Competitiveness Through Innovation and Value
Enhancement) initiative in an attempt to add value to the delivery of projects. This research
explored the congruence and scope for incorporating the ACTIVE principles into current
competency frameworks in use by project organizations. An interpretive and qualitative
research approach was adopted, using semi-structured interviews with eight Project
Managers and Learning and Development Managers in project organizations. The use of
competency frameworks is not as widespread as first thought. Current competency
frameworks in use in project organizations are based on a fairly comprehensive body of
knowledge and largely congruent with the ACTIVE principles centered around concept
definition, team management, supply chain relationship management, communication, risk
management, innovation, project execution and performance measurement. However,
ACTIVE principlesâ underpinning ethos of creating a collaborative working environment in
projects is a missing piece worthy of incorporation into competency frameworks currently in
use in project organizations
Predicting precipitation kinetics during the annealing of additive manufactured inconel 625 components
The prediction of solidification microstructures associated with additive manufacture of metallic components is fundamental in the identification scanning strategies, process parameters and subsequent heat treatments for optimised component properties. Interactions between the powder particles and the laser heat source result in complex thermal fields in and around the metal melt pool, which will influence the spatial distribution of chemical species as well as solid-state precipitation reactions. This paper demonstrates that a multi-component, multi-phase precipitation model can successfully predict the observed precipitation kinetics in Inconel 625, capturing the anomalous precipitation behaviour exhibited in additively manufactured components. A computer coupling of phase diagrams and thermochemistry (CALPHAD)-based approach captures the impact of dendritic segregation of alloying elements upon precipitation behaviour. The model was successful in capturing the precipitation kinetics during annealing considering the Nb-rich and Nb-depleted regions that are formed during additive manufacturing
Noncommutative Topological Half-flat Gravity
We formulate a noncommutative description of topological half-flat gravity in
four dimensions. BRST symmetry of this topological gravity is deformed through
a twisting of the usual BRST quantization of noncommutative gauge theories.
Finally it is argued that resulting moduli space of instantons is characterized
by the solutions of a noncommutative version of the Plebanski's heavenly
equation.Comment: 12+1 pages, revtex4, no figure
PHYLO-ASP: Phylogenetic Systematics with Answer Set Programming
This note summarizes the use of Answer Set Programming to solve various computational problems to infer phylogenetic trees and phylogenetic networks, and discusses its applicability and effectiveness on some real taxa
Space-time evolution of hadronization
Beside its intrinsic interest for the insights it can give into color
confinement, knowledge of the space-time evolution of hadronization is very
important for correctly interpreting jet-quenching data in heavy ion collisions
and extracting the properties of the produced medium. On the experimental side,
the cleanest environment to study the space-time evolution of hadronization is
semi-inclusive Deeply Inelastic Scattering on nuclear targets. On the
theoretical side, 2 frameworks are presently competing to explain the observed
attenuation of hadron production: quark energy loss (with hadron formation
outside the nucleus) and nuclear absorption (with hadronization starting inside
the nucleus). I discuss recent observables and ideas which will help to
distinguish these 2 mechanisms and to measure the time scales of the
hadronization process.Comment: 6 pages, 4 figures. Based on talks given at "Hot Quarks 2006",
Villasimius, Italy, May 15-20, 2006, and at the "XLIV internataional winter
meeting on nuclear physics", Bormio, Italy, Jan 29 - Feb 5, 2006. To appear
in Eur.Phys.J.
Hadron Multiplicities
We review results on hadron multiplicities in high energy particle
collisions. Both theory and experiment are discussed. The general procedures
used to describe particle multiplicity in Quantum Chromodynamics (QCD) are
summarized. The QCD equations for the generating functions of the multiplicity
distributions are presented both for fixed and running coupling strengths. The
mean multiplicities of gluon and quark jets, their ratio, higher moments, and
the slopes of multiplicities as a function of energy scale, are among the main
global features of multiplicity for which QCD results exist. Recent data from
high energy e+e- experiments, including results for separated quark and gluon
jets, allow rather direct tests of these results. The theoretical predictions
are generally quite successful when confronted with data. Jet and subjet
multiplicities are described. Multiplicity in limited regions of phase space is
discussed in the context of intermittency and fractality. The problem of
singularities in the generating functions is formulated. Some special features
of average multiplicities in heavy quark jets are described.Comment: 140 pages, 33 figures, version for Physics Report
Anomalous Pseudoscalar-Photon Vertex In and Out of Equilibrium
The anomalous pseudoscalar-photon vertex is studied in real time in and out
of equilibrium in a constituent quark model. The goal is to understand the
in-medium modifications of this vertex, exploring the possibility of enhanced
isospin breaking by electromagnetic effects as well as the formation of neutral
pion condensates in a rapid chiral phase transition in peripheral,
ultrarelativistic heavy-ion collisions. In equilibrium the effective vertex is
afflicted by infrared and collinear singularities that require hard thermal
loop (HTL) and width corrections of the quark propagator. The resummed
effective equilibrium vertex vanishes near the chiral transition in the chiral
limit. In a strongly out of equilibrium chiral phase transition we find that
the chiral condensate drastically modifies the quark propagators and the
effective vertex. The ensuing dynamics for the neutral pion results in a
potential enhancement of isospin breaking and the formation of
condensates. While the anomaly equation and the axial Ward identity are not
modified by the medium in or out of equilibrium, the effective real-time
pseudoscalar-photon vertex is sensitive to low energy physics.Comment: Revised version to appear in Phys. Rev. D. 42 pages, 4 figures, uses
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