Dr Michael Teper

Abstract:

We present the results of a detailed calculation of the excitation spectrum of states with quantum numbers JPC = 0++, 1- and 2++ in the three-dimensional SU(2) Higgs model at two values of the scalar self-coupling and for fixed gauge coupling. We study the properties of Polyakov loop operators, which serve to test the confining properties of the model in the symmetric phase. At both values of the scalar coupling we obtain masses of bound states consisting entirely of gauge degrees of freedom (glueballs), which are very close to those obtained in the pure gauge theory. We conclude that the previously observed, approximate decoupling of the scalar and gauge sectors of the theory persists at large scalar couplings. We study the crossover region at large scalar coupling and present a scenario how the confining properties of the model in the symmetric phase are lost inside the crossover by means of flux tube decay. We conclude that the underlying dynamics responsible for the observed dense spectrum of states in the Higgs region at large couplings must be different from that in the symmetric phase. © 1998 Elsevier Science B.V.

Abstract:

We investigate the topological structure of the vacuum in SU(3) lattice gauge theory. We use under-relaxed cooling to remove the high-frequency fluctuations and a variety of "filters" to identify the topological charges in the resulting smoothened field configurations. We find a densely packed vacuum with an average instanton size, in the continuum limit, of ρ̄∼0.5 fm. The density at large ρ decreases paidly as 1/ρ∼11. At small sizes we see some signs of a trend towards the asymptotic perturbative behavior of D(∝)ρ6. We find that an interesting polarization phenomenon occurs: the large topological charges tend to have, on the average, the same sign and are over-screened by the smaller charges which tend to have, again on the average, the opposite sign to the larger instantons. We also calculate the topological susceptibility, χt, for which we obtain a continuum value of χ1/4t∼187 MeV. We perform the calculations for various volumes, lattice spacings and numbers of cooling sweeps, so as to obtain some control over the associated systematic errors. The coupling range is 6.0≤β≤6.4 and the lattice volumes range from 163×48 to 323×64.

Abstract:

The spectrum for the pure gauge sector is calculated for an extended Isgur-Paton model in 2+1 and 3+1 dimensions and compared to recent lattice calculations of the glueball spectrum. The IP model is extended by inclusion of a rigidity (curvature) term and, in D=2+1, mixing through a higer topological contribution. For a choice of parameterizations, near quantitative agreement is found for SU(3) in D=2+1, but in D=3+1 the extensions fail to remedy the qualitative disagreement.

Abstract:

In the maximally Abelian gauge of SU(2), the clusters of monopole current are found to divide into two distinct classes. The largest cluster permeates the lattice, has a density that scales and produces the string tension. The remaining clusters possess an approximate 1/l3 number density distribution (1 is the cluster length), their radii vary as √1 and their total current density does not scale. Their contribution to the string tension is compatible with being exactly zero. Their number density can be thought of as arising from an underlying scale invariant distribution. This suggests that they are not related to instantons. We also observe that when we locally smoothen the SU(2) fields by cooling, the string tension due to monopoles becomes much smaller than the SU(2) string tension. This dramatic loss of Abelian/monopole dominance occurs even after just one cooling step.