Some properties of renormalons in gauge theories

We find the explicit operatorial form of renormalon-type singularities in abelian gauge theory. Local operators of dimension six take care of the first U.V. renormalon, non local operators are needed for I.R. singularities. In the effective lagrangian constructed with these operators non local imaginary parts appearing in the usual perturbative expansion at large orders are cancelled.Comment: 17 pages + uuencoded file with 7 figures, REVTeX, IFUP-TH-31-9

Renormalons in the effective potential of the vectorial (φ⃗2)2(\vec{\varphi}^{2})^{2} model

We study the properties of ultraviolet renormalons in the vectorial $(\vec{\phi}^{2})^{2}$ model. This is achieved by studying the effective potential of the theory at next to leading order of the $1/N$ expansion, the appearence ofthe renormalons in the perturbative series and their relation to the imaginary part of the potential. We also consider the mechanism of renormalon cancellation by `irrelevant" higher dimensional operators.Comment: 20 pages, Latex, 3 Postscript figure

Condensation of vortices and disorder parameter in 3d Heisenberg model

The 3d Heisenberg model is studied from a dual point of view. It is shown that the disordered phase corresponds to condensation of vortices in the vacuum, and the critical indices are computed from the corresponding disorder parameter.Comment: LATTICE98(spin

A disorder analysis of the Ising model

Lattice studies of monopole condensation in QCD are based on the construction of a disorder parameter, a creation operator of monopoles which is written in terms of the gauge fields. This procedure is expected to work for any system which presents duality. We check it on the Ising model in 2d, which is exactly solvable. The output is an amusing exercise in statistical mechanics.Comment: 14 pages, 3 figure

A disorder parameter for dual superconductivity in gauge theories

Dual superconductivity in the confining phase of gauge theories is discussed in terms of a disorder parameter which vanishes in normal phase and is different from zero in the superconducting phase.Comment: 3 pages, 4 postscript figures, espcrc2, epsfig latex styles, Contribution to Lat 97 Conference, Edinburg

Dual vortices in Abelian projected SU(2) in the Polyakov gauge

We study dual Abrikosov vortices in Abelian projected SU(2) gauge theory in the Polyakov gauge. We show that vortices are present in this gauge but they are suppressed with respect to the maximal Abelian gauge. We interpret this difference in terms of the shielding of the electric charge by the charged coset fields.Comment: Talk presented at LATTICE96(topology), 3 pages, latex, 4 eps figures, uses epsfig and espcrc2.sty (included

Condensation of vortices in the X-Y model in 3d: a disorder parameter

A disorder parameter is constructed which signals the condensation of vortices. The construction is tested by numerical simulations.Comment: 9 pages, 5 postscript figures, typset using REVTE

More on ambiguities in the pole mass

The relation between the pole quark mass and the $\overline{MS}$-renormalized mass is governed by an infrared renormalon singularity, which leads to an ambiguity of order $\Lambda_{QCD}$ in the definition of the pole mass. We use the renormalization group and heavy quark effective theory to determine the exact nature of this singularity up to an overall normalization. In the abelian gauge theory, the normalization is computed partially to next-to-leading order in the flavour expansion.Comment: LaTeX, 10 pages, Figures appended as uu-encoded file, UM-TH-94-3