Dr Michael Teper

Abstract:

The phase diagram is investigated for SU(2) lattice gauge theory in d = 3, coupled to adjoint scalars. For small values of the quartic scalar coupling, λ, the transition separating Higgs and confinement phases is found to be first-order, in agreement with earlier work by Nadkarni. The surface of second-order transitions conjectured by Nadkarni, however, is shown instead to correspond to crossover behaviour. This conclusion is based on a finite size analysis of the scalar mass and susceptibility. The nature of the phase transition at the termination of first-order behaviour is investigated and we find evidence for a critical point at which the scalar mass vanishes. The photon mass and confining string tension are measured and are found to be negligibly small in the Higgs phase. This is correlated with the very small density of magnetic monopoles in the Higgs phase. The string tension and photon mass rise rapidly as the crossover is traversed towards the symmetric phase. © 1997 Elsevier Science B.V.

Abstract:

We study the detailed properties of [Formula presented] domain walls in the deconfined high-temperature phase of the [Formula presented] SU(2) gauge theory. These walls are studied both by computer simulations of the lattice theory and by one-loop perturbative calculations. The latter are carried out both in the continuum and on the lattice. We find that leading order perturbation theory reproduces the detailed properties of these domain walls remarkably accurately even at temperatures where the effective dimensionless expansion parameter [Formula presented] is close to unity. The quantities studied include the surface tension, the action density profiles, roughening, and the electric screening mass. It is only for the last quantity that we find an exception to the precocious success of perturbation theory. All this shows that, despite the presence of infrared divergences at higher orders, high-[Formula presented] perturbation theory can be an accurate calculational tool. © 1997 The American Physical Society.

Abstract:

We fix SU(2) lattice gauge fields to the maximally Abelian gauge in both three and four dimensions. We extract the corresponding U(1) fields and monopole current densities and calculate separately the confining string tensions arising from these U(1) fields and monopole “condensates.” We generate multiple Gribov copies and study how the U(1) fields and monopole distributions vary between these different copies. As expected, we find substantial variations in the number of monopoles, their locations, and in the values of the U(1) field strengths. The string tensions extracted from “extreme” Gribov copies also differ but this difference appears to be no more than about 20%. We also directly compare the fields of different Gribov copies. We find that on the distance scales relevant to confinement, the U(1) and monopole fluxes that disorder Wilson loops are highly correlated between these different Gribov copies. All this suggests that while there is indeed a Gribov copy problem the resulting ambiguity is, in this gauge and for the study of confinement, of limited importance. © 1997 The American Physical Society.

Abstract:

We present results for the masses of the low-lying states with quantum numbers 0++, 2++ and 1-- as well as Polyakov line correlations in the Higgs and confinement regions of the 3d SU(2) Higgs model. In the confinement phase we find a dense spectrum of bound states approximately split into two disjoint sectors. One consists of W-balls nearly identical to the glueball spectrum of the pure gauge theory, the other of bound states of scalars.