Gauge Invariant Field Strength Correlators Research Articles

Gauge-invariant field-strength correlators for QCD in a magnetic background

We consider the properties of the gauge-invariant two-point correlation functions of the gauge-field strengths for QCD in the presence of a magnetic background field. We discuss the general structure of the correlators in this case and provide the results of an exploratory lattice study for $N_f = 2$ QCD discretized with unimproved staggered fermions. Our analysis provides evidence for the emergence of anisotropies in the non-perturbative part of the correlators and for an increase of the gluon condensate as a function of the external magnetic field.

Semi-analytic calculation of the monopole order parameter in QCD

The monopole order parameter of QCD is computed in terms of gauge invariant field strength correlators. Both quantities are partially known from numerical simulations on the lattice. A new insight results on the structure of the confining vacuum.

Analytic estimate of the order parameter for monopole condensation in QCD

The disorder parameter for the condensation of monopoles in QCD is estimated analytically in terms of gauge invariant field-strength correlators. The continuum limit is discussed.

Gauge-invariant field-strength correlators in pure Yang-Mills theory and full QCD at finite temperature

We study by numerical simulations on a lattice the behaviour of the gauge-invariant two-point correlation functions of the gauge-field strengths across the deconfinement phase transition, both for the pure-gauge SU(3) theory and for full QCD with two flavours. Quenched data agree within errors with previous determinations, but have much higher statistics. A best-fit analysis of the data has been performed, both for the quenched and the full-QCD case, showing that the electric gluon condensate drops to zero at the deconfining phase transition.

On the dependence of the gauge-invariant field-strength correlators in QCD on the shape of the Schwinger string

We study, by numerical simulations on a lattice, the dependence of the gauge-invariant two-point field-strength correlators in QCD on the path used to perform the color parallel transport between the two points.

Confinement, chiral symmetry breaking, and the axial anomaly from domain formation at intermediate resolution

Based on general renormalization group arguments, Polyakov's loop-space formalism, and recent analytical lattice arguments, suggesting, after Abelian gauge fixing, a description of pure gluodynamics by means of a Georgi-Glashow like model, the corresponding vacuum fields are defined in a nonlocal way. Using lattice information on the gauge invariant field strength correlator in full QCD, the resolution scale ${\ensuremath{\Lambda}}_{b},$ at which these fields become relevant in the vacuum, is determined. For SU(3) gauge theory it is found that ${\ensuremath{\Lambda}}_{b}\ensuremath{\sim}2.4$ GeV, 3.1 GeV, and 4.2 GeV for ${(N}_{F}=4,$ ${m}_{q}=18$ MeV), ${(N}_{F}=4,$ ${m}_{q}=36$ MeV), and pure gluodynamics, repectively. Implications for the operator product expansion of physical correlators are discussed. It is argued that the emergence of magnetic (anti)monopoles in the vacuum at resolution ${\ensuremath{\Lambda}}_{b}$ is a direct consequence of the randomness in the formation of a low entropy Higgs condensate. This implies a breaking of chiral symmetry and a proliferation of the axial U(1) anomaly at this scale already. Justifying Abelian projection, a decoupling of non-Abelian gauge field fluctuations from the dynamics occurs. The condensation of (anti)monopoles at ${\ensuremath{\Lambda}}_{c}<{\ensuremath{\Lambda}}_{b}$ follows from the demand that vacuum fields ought to have vanishing action at any resolution. As monopoles condense they are reduced to their cores, and hence they become massless. Apparently broken gauge symmetries at resolutions ${\ensuremath{\Lambda}}_{c}<\ensuremath{\Lambda}<~{\ensuremath{\Lambda}}_{b}$ are restored in this process.

Nonperturbative corrections to the Drell-Yan transverse momentum distribution

We study nonperturbative corrections to the transverse momentum distribution of vector bosons in the Drell-Yan process. Factorizing out the Sudakov effects due to soft gluons we express their contribution to the distribution in the form of the vacuum averaged Wilson loop operator. We calculate the nonperturbative contribution to the Sudakov form factor using the expansion of the Wilson loop over vacuum fields supplemented with the expression for nonlocal gauge invariant field strength correlator. Although the Wilson loop is defined in an essentially Minkowski kinematics, the part of the nonperturbative contribution depending on the invariant mass of the produced vector bosons is governed by asymptotics of the correlator at large space-like (Euclidean) separations and therefore can be calculated using conventional nonperturbative methods. Applying the results of lattice calculations we found that the obtained expression for the nonperturbative power corrections is in qualitative agreement with known phenomenological expressions at large transverse momenta and deviate from them at small transverse momenta.

Gauge invariant field strength correlators from RG smoothing and color correlations between topological charge clusters

Using the renormalization group based smoothing technique we have studied the gauge invariant field strength correlator at T ≠ 0 and T = 0 in pure SU(2) gauge theory. In conjunction with a cluster analysis, the field strength correlator is used to study correlations between the clusters in space and color orientation.

Gauge invariant field strength correlators from RG smoothing and color correlations between topological charge clusters

Gauge invariant field strength correlators from RG smoothing and color correlations between topological charge clusters

Field strength correlators in QCD: new fits to the lattice data

We discuss the results obtained by fitting the lattice data of the gauge-invariant field strength correlators in QCD with some particular functions which are commonly used in the literature in some phenomenological approaches to high-energy hadron–hadron scattering. A comparison is done with the results obtained in the original fits to the lattice data.

Gauge invariant field strength correlators and Abelian dominance in QCD

We establish a relation between the two-point field strength correlator in QCD and the dual field propagator of the effective dual Abelian Higgs model describing the infrared behaviour of QCD.

Gauge-invariant field strength correlators in full QCD

We study, by numerical simulations on a lattice, the behaviour of the gauge-invariant correlation functions of the gauge field strengths in the QCD vacuum with four flavours of dynamical staggered fermions.