Extended Double Lattice BRST, Curci-Ferrari Mass and the Neuberger Problem

We present Extended Double BRST on the lattice and extend the Neuberger problem to include the ghost/anti-ghost symmetric formulation of the non-linear covariant Curci-Ferrari (CF) gauges. We then show how a CF mass regulates the 0/0 indeterminate form of physical observables, as observed by Neuberger, and discuss the gauge-parameter and mass dependence of the model.Comment: Prepared for 7th Conference on Quark Confinement and the Hadron Spectrum, Ponta Delgada, Azores, Portugal, 2-7 Sep 2006. 3p

Finite element simulation of semi-finishing turning of Electron Beam Melted Ti6Al4V under dry and cryogenic cooling

open6noIn the last few years, important step forwards have been made on Finite Element Simulation of machining operations. Wrought Ti6Al4V alloy has been deeply investigated both numerically and experimentally due to its wide application in the industry. Recently, Additive Manufacturing technologies as the Electron Beam Melting and the Direct Melting Laser Sintering are more and more employed in the production of biomedical and aeronautical components made of Ti6Al4V alloy. Fine acicular microstructures are generated by the application of additive manufacturing technologies, affecting the mechanical properties and the machinability. By the consequence, this peculiarity has to be considered in modelling the material behaviour. In this work, a numerical analysis of cylindrical external turning on Electron Beam Melted (EBM) Ti6Al4V alloy is presented. A Johnson-Cook constitutive equation was implemented as a flow stress model and adapted with respect to the wrought Ti6Al4V alloy. The model was calibrated and validated through the cutting forces and temperatures measurements acquired under dry and cryogenic lubricating conditions.openBordin, A; Imbrogno, S.; Rotella, G.; Bruschi, S.; Ghiotti, A.; Umbrello, D.Bordin, Alberto; Imbrogno, S.; Rotella, G.; Bruschi, Stefania; Ghiotti, Andrea; Umbrello, D

Material behaviour at low temperatures for calibrating cryogenic machining numerical simulations

Abstract Recently, cryogenic machining of difficult-to-cut alloys has been adopted to increase tool life and improve the machined components surface integrity. Numerical models of cryogenic machining are being developed to evaluate the influence of the different process parameters. Up to now, their calibration in terms of material flow stress is fulfilled using data at conventional temperatures, whereas the material sensitivity to temperatures lower than the environment one should be taken into account. To this regard, the paper objective is to present material data, obtained through a newly developed Split Hopkinson Tension Bar, at cryogenic temperatures and high strain rates to properly calibrate cryogenic machining numerical models

Decontracted double BRST on the lattice

We present the Curci-Ferrari model on the lattice. In the massless case the topological interpretation of this model with its double BRST symmetry relates to the Neuberger 0/0 problem which we extend to include the ghost/anti-ghost symmetric formulation of the non-linear covariant Curci-Ferrari gauges on the lattice. The introduction of a Curci-Ferrari mass term, however, serves to regulate the 0/0 indeterminate form of physical observables observed by Neuberger. While such a mass m decontracts the double BRST/anti-BRST algebra, which is well-known to result in a loss of unitarity, observables can be meaningfully defined in the limit m to 0 via l'Hospital's rule. At finite m the topological nature of the partition function used as the gauge fixing device seems lost. We discuss the gauge parameter xi and mass m dependence of the model and show how both cancel when m = m(xi) is appropriately adjusted with xi.Comment: 18 pages, no figure

Les nouveaux arrangements territoriaux de la gestion de l'eau potable

Sous l’effet d’alertes portant sur la quantité et la qualité des ressources disponibles et sur l’état du patrimoine « réseaux », conjuguées à une pression politico-réglementaire multiforme, les acteurs territoriaux de l’eau potable ont engagé au début des années 1990 un long processus visant à réformer leur organisation. L’enjeu n’est plus tant celui de la desserte universelle de l’eau potable à domicile, désormais achevée, que celui de la « sécurisation » de ce service public. Ce nouvel impératif consiste à assurer une alimentation en eau potable de qualité et en continu, pour un coût – économique et environnemental – acceptable. Le présent article revient sur les enseignements ayant trait à la dimension multiscalaire de la gestion de l’eau, et aux dynamiques concourant à faire émerger de nouveaux arrangements territoriaux . En s’attachant au processus de recomposition de la gestion de l’eau à l’échelle départementale, il s’agit d’une part de mettre en évidence le changement d’un programme d’action, passant d’un impératif de desserte universelle de l’eau potable à domicile à une injonction à la sécurisation. D’autre part, cela permet d’insister sur la dimension contingente de ces recompositions et des nouvelles formes d’organisation, provenant en partie des jeux politico-institutionnels

Sigma Terms of Light-Quark Hadrons

A calculation of the current-quark mass dependence of hadron masses can help in using observational data to place constraints on the variation of nature's fundamental parameters. A hadron's sigma-term is a measure of this dependence. The connection between a hadron's sigma-term and the Feynman-Hellmann theorem is illustrated with an explicit calculation for the pion using a rainbow-ladder truncation of the Dyson-Schwinger equations: in the vicinity of the chiral limit sigma_pi = m_pi/2. This truncation also provides a decent estimate of sigma_rho because the two dominant self-energy corrections to the rho-meson's mass largely cancel in their contribution to sigma_rho. The truncation is less accurate for the omega, however, because there is little to compete with an omega->rho+pi self-energy contribution that magnifies the value of sigma_omega by ~25%. A Poincare' covariant Faddeev equation, which describes baryons as composites of confined-quarks and -nonpointlike-diquarks, is solved to obtain the current-quark mass dependence of the masses of the nucleon and Delta, and thereby sigma_N and sigma_Delta. This "quark-core" piece is augmented by the "pion cloud" contribution, which is positive. The analysis yields sigma_N~60MeV and sigma_Delta~50MeV.Comment: 22 pages, reference list expande