The UA(1)U_A(1) Problem on the Lattice

If the expression of the topological charge density operator, suggested by fermions obeying the Ginsparg--Wilson relation, is employed, it is possible to prove on the lattice the validity of the Witten--Veneziano formula for the $\eta'$ mass. Recent numerical results from simulations with overlap fermions in 2 (abelian Schwinger model) and 4 (QCD) dimensions give values for the mass of the lightest pseudo-scalar flavour-singlet state that agree with theoretical expectations and/or experimental data.Comment: 3 pages, talk presented by G.C. Rossi at Lattice2001(theorydevelop

High Friction Surfacing Systems Using Blends of Natural Aggregate and Calcined Bauxite

High friction surfacing (HFS), bonded to a road surface at high risk locations, has beenshown to significantly reduce road fatalities and serious injuries, i.e., HFS saves lives. Calcinedbauxite is the preferred aggregate for use in HFS systems due to its unique ability to resistpolishing and abrasion by vehicle tires. Calcined bauxite is expensive, negatively impacts theenvironment due to mining, production and transporting processes and has come under supplypressures in recent years. This paper investigates the potential for blending natural aggregates withcalcined bauxite for use in HFS systems. The experiments involved subjecting HFS specimens tolaboratory simulated trafficking and testing for skid resistance, texture depth and mass loss. Thetesting was carried out in laboratories in Spain and Northern Ireland. The findings suggest thatthere is the potential to reduce the amount of calcined bauxite used in HFS systems by replacing apercentage of the calcined bauxite with high PSV natural sandstone or volcanic tuff aggregate. Theimpact of this research could reduce the risks associated with supply issues to the HFS industry,reduce environmental impact by using less calcined bauxite in HFS systems and reduce costsassociated with the aggregate component of HFS systems—enabling road authorities to installmore systems at high risk locations to further reduce fatalities and serious injuries on their road

Fracture functions from cut vertices

Using a generalized cut vertex expansion we introduce the concept of an extended fracture function for the description of semi-inclusive deep inelastic processes in the target fragmentation region. Extended fracture functions are shown to obey a standard homogeneous DGLAP-type equation which, upon integration over t, becomes the usual inhomogeneous evolution equation for ordinary fracture functions.Comment: latex, 15 pages including 7 postscript figure

Confinement in QCD

The guiding lines of lattice investigations on colour confinement are reviewed, together with recent results.Comment: 7 pages,3 figures, Plenary talk at PANIC'99,10-16 June 1999,Uppsal

A Brief Introduction to Wilson Loops and Large N

A pedagogical introduction to Wilson loops, lattice gauge theory and the 1/N-expansion of QCD is presented. The three introductory lectures were given at the 37th ITEP Winter School of Physics, Moscow, February 9-16, 2009.Comment: 14 pages, 14 figures, Lectures at the 37th ITEP Winter School of Physic