Status of center dominance in various center gauges

We review arguments for center dominance in center gauges where vortex locations are correctly identified. We introduce an appealing interpretation of the maximal center gauge, discuss problems with Gribov copies, and a cure to the problems through the direct Laplacian center gauge. We study correlations between direct and indirect Laplacian center gauges.Comment: Presented by S. Olejnik at the NATO Advanced Research Workshop "Confinement, Topology, and other Non-Perturbative Aspects of QCD", Jan. 21-27, 2002, Stara Lesna, Slovakia. 10 pages, 3 figures (8 EPS files), uses crckapb.st

Academic freedom and changing focus on student assessment in Dutch higher education

The paper addresses this issue of academic freedom by exploring how the new regulation regarding student assessment procedures has been implemented in Dutch higher education institutions. We endeavour to understand how teaching staff have responded to the new rules and to what extent decision-making processes have included teaching staff. To answer our research question, we would like to concentrate on two issues: the role of the Examination Board and the design of the assessment procedures. Our working hypothesis is that new institutional arrangements of student assessments reduce academic freedom. Previous research has showed that academics largely engage in symbolic compliance with the imperatives of management requirements while keeping their academic freedom intact (Leisyte and Dee 2012). Universities in their turn, are increasingly acting as strategic actors in not only complying but also shaping their institutional environments (Meyer and Rowan 1977, Greenwood and Hinnings 1996, Krücken 2011). The responses to established norms and beliefs range from passivity to increasingly active resistance (Oliver 1991). We will discuss if the impingement on academic freedom is offset by increased assurance of quality for students, and explore how to balance the two values of freedom and quality. Methods used are document analysis and interviews with teachers, university administrators and during Fall 2011 in the frame of the Identifying Barriers in promoting European Standards and Guidelines for Quality Assurance (IBAR) project

Vortex solution in 2+1 dimensional Yang-Mills theory at high temperatures

At high temperatures the A_0 component of the Yang--Mills field plays the role of the Higgs field, and the 1-loop potential V(A_0) plays the role of the Higgs potential. We find a new stable vortex solution of the Abrikosov-Nielsen-Olesen type, and discuss its properties and possible implications.Comment: 8 p., three .eps figures include

Detection of Center Vortices in the Lattice Yang-Mills Vacuum

We discuss the implementation of the ``direct'' maximal center gauge (a gauge which maximizes the lattice average of the squared-modulus of the trace of link variables), and its use in identifying Z(2) center vortices in Yang-Mills vacuum configurations generated by lattice Monte Carlo. We find that center vortices identified in the vacuum state account for the full asymptotic string tension. Scaling of vortex densities with lattice coupling, change in vortex size with cooling, and sensitivity to Gribov copies is discussed. Preliminary evidence is presented, on small lattices, for center dominance in SU(3) lattice gauge theory.Comment: 28 pages including 18 figures, Latex2

Charge Screening, Large-N, and the Abelian Projection Model of Confinement

We point out that the abelian projection theory of quark confinement is in conflict with certain large-N predictions. According to both large-N and lattice strong-coupling arguments, the perimeter law behavior of adjoint Wilson loops at large scales is due to charge-screening, and is suppressed relative to the area term by a factor of $1/N^2$. In the abelian projection theory, however, the perimeter law is due to the fact that $N-1$ out of $N^2-1$ adjoint quark degrees of freedom are (abelian) neutral and unconfined; the suppression factor relative to the area law is thus only $1/N$. We study numerically the behavior of Wilson loops and Polyakov lines with insertions of (abelian) charge projection operators, in maximal abelian gauge. It appears from our data that the forces between abelian charged, and abelian neutral adjoint quarks are not significantly different. We also show via the lattice strong-coupling expansion that, at least at strong couplings, QCD flux tubes attract one another, whereas vortices in type II superconductors repel.Comment: 20 pages (Latex), 8 figures, IFUP-TH 54/9

The Higgs field and the ultraviolet behaviour of the vortex operator in 2+1 dimensions

We calculate the change in the ultraviolet behaviour of the vortex operator due to the presence of dynamical Higgs field in both 2+1 dimensional QED and the 2+1 dimensional Georgi-Glashow model. We find that in the QED case the presence of the Higgs field leads at the one loop level to power like correction to the propagator of the vortex operator. On the other hand, in the Georgi-Glashow model, the adjoint Higgs at one loop has no affect on the vortex propagator. Thus, as long as the mass of the Higgs field is much larger than the gauge coupling constant, the ultraviolet behaviour of the vortex operator in the Georgi-Glashow model is independent of the Higgs mass.Comment: 14 page