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

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

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

Surface acidity of η-alumina. Part 2. Interaction of pyridine with other adsorbates

The interaction of Py with other adsorbates, whose behaviour was investigated previously, is studied here by i.r. spectroscopy and microgravimetry, both to confirm previous assignments and to gain new information on the nature of alumina surface sites. Py/CO interactions reveal that the strongest Lewis acidic sites (AlcusIV ions) are heterogeneous, whereas the adsorption of Py alone and the use of any simple surface model does not show this. Py/H2O interactions indicate that Py adsorbed at AlcusIV ions is selectively and non reversibly removed, as these sites are the favoured centres for surface rehydration. Other weaker Lewis adsorbed Py species are, in contrast, involved in surface equilibria with adsorbing water. Py/CO2 interactions indicate that Py Lewis coordination inhibits σ-coordination of CO 2 and that it induces an unusual basicity in surface oxygens, so that monodentate and bidenate carbonates are formed upon CO2 uptake. However, two types of surface bicarbonates are inhibited, either through the coordination of Py at the proper acidic centre, or through strong H bonding between Lewis coordinated Py and the "reactive" hydroxyl. Chemical evidence is found for cooperative effects and lateral interactions involving coordinated Py species, which were previously postulated on the basis of the spectroscopic features of adsorbed species