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B. Lucini

Publications and source records attributed to B. Lucini.

47 records · Page 3Linked to original sources
arXiv2000

Monopoles, vortices and confinement in SU(3) gauge theory

We compute, in SU(3) pure gauge theory, the vacuum expectation value (vev) of the operator which creates a $Z_3$ vortex wrapping the lattice through periodic boundary conditions (dual Polyakov line). The technique used is the same already tested in the SU(2) case. The dual Polyakov line proves to be a good disorder parameter for confinement, and has a similar behaviour to the monopole condensate. The new features which characterise the construction of the disorder operator in SU(3) are emphasised.

hep-lat↗
arXiv2000

Z2 monopoles in D=2+1 SU(2) lattice gauge theory

We calculate the Euclidean action of a pair of Z2 monopoles (instantons), as a function of their spatial separation, in D=2+1 SU(2) lattice gauge theory. We do so both above and below the deconfining transition at T=Tc. At high T, and at large separation, we find that the monopole `interaction' grows linearly with distance: the flux between the monopoles forms a flux tube (exactly like a finite portion of a Z2 domain wall) so that the monopoles are linearly confined. At short distances the interaction is well described by a Coulomb interaction with, at most, a very small screening mass, possibly equal to the Debye electric screening mass. At low T the interaction can be described by a simple screened Coulomb (i.e. Yukawa) interaction with a screening mass that can be interpreted as the mass of a `constituent gluon'. None of this is unexpected, but it helps to resolve some apparent controversies in the recent literature.

hep-lat↗
arXiv2000

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.

hep-lat↗
arXiv2000

Vortices and confinement in hot and cold D=2+1 gauge theories

We calculate the variation with temperature of the vortex free energy in D=2+1 SU(2) lattice gauge theories. We do so both above and below the deconfining transition at T=Tc. We find that this quantity is zero at all T for large enough volumes. For T Tc it is consistent with the conventional expectation of `spatial' linear confinement. In small spatial volumes this quantity is shown to be non-zero. The way it decreases to zero with increasing volume is shown to be controlled by the (spatial) string tension and it has the functional form one would expect if the vortices being studied were responsible for the confinement at low T, and for the `spatial' confinement at large T. We also discuss in detail some of the direct numerical evidence for a non-zero spatial string tension at high T, and we show that the observed linearity of the (spatial) potential extends over distances that are large compared to typical high-T length scales.

hep-lat↗
arXiv2000

Implementation of C* boundary conditions in the Hybrid Monte Carlo algorithm

In the study of QCD dynamics, C* boundary conditions are physically relevant in certain cases. In this paper we study the implementation of these boundary conditions in the lattice formulation of full QCD with staggered fermions. In particular, we show that the usual even-odd partition trick to avoid the redoubling of the fermion matrix is still valid in this case. We give an explicit implementation of these boundary conditions for the Hybrid Monte Carlo algorithm.

hep-lat↗
arXiv1999

Colour confinement and dual superconductivity of the vacuum - I

We study dual superconductivity of the ground state of SU(2) gauge theory, in connection with confinement. We do that measuring on the lattice a disorder parameter describing condensation of monopoles. Confinement appears as a transition to dual superconductor, independent of the abelian projection defining monopoles. Some speculations are made on the existence of a more appropriate disorder parameter. A similar study for SU(3) is presented in a companion paper.

hep-lat↗
arXiv1999

Colour confinement and dual superconductivity of the vacuum - II

The dual superconductivity of the vacuum in SU(3) gauge theory is investigated by constructing a disorder parameter which signals monopole condensation in various abelian projections and by studying numerically on the lattice its behaviour at finite temperature. We find that the vacuum is a dual superconductor with respect to each U(1) of the residual gauge group after abelian projection independently of the abelian projection chosen. Like in the SU(2) case (discussed in a companion paper) a finite size scaling analysis enables us to extract the indices of the phase transition and our analysis is consistent with independent determinations.

hep-lat↗
arXiv1999

What We Do Understand of Colour Confinement

The status of our understanding of confinement is reviewed. The evidence from lattice is that monopole condensation, or dual superconductivity, is at work. Confinement is an order-disorder transition. Different monopole species look equivalent, indicating that the symmetry of the disordered phase is more interesting that we understand.

hep-lat↗
arXiv1998

Monopole Condensation and Color Confinement

New evidence is discussed of monopole condensation in the vacuum of SU(2) and SU(3) gauge theories. Monopoles defined by different abelian projections do condense in the transition to the confined phase and show the same behavior. For SU(2) critical indices are determined by finite size scaling analysis and the results agree with the 3d Ising Model, as expected.

hep-lat↗
arXiv1998

Progress in understanding colour confinement

New results from lattice are presented,which demonstrate that monopoles condense in the vacuum of confined phase of QCD, which is thus a dual superconductor. Monopoles defined by different abelian projections appear to be physically equivalent.

hep-lat↗