J. Micheli

On the IR behaviour of the Landau-gauge ghost propagator

We examine analytically the ghost propagator Dyson-Schwinger Equation (DSE) in the deep IR regime and prove that a finite ghost dressing function at vanishing momentum is an alternative solution (solution II) to the usually assumed divergent one (solution I). We furthermore find that the Slavnov-Taylor identities discriminate between these two classes of solutions and strongly support the solution II. The latter turns out to be also preferred by lattice simulations within numerical uncertainties.

Asymptotic behavior of the gluon propagator from lattice QCD

We study the flavorless gluon propagator in the Landau gauge from high statistics lattice calculations. Hypercubic artifacts are efficiently eliminated by taking the P p 4 → 0 limit. The propagator is fitted to the three-loops perturbative formula in an energy window ranging form ∼ 2.5 GeV up to ∼ 5.5 GeV. �s is extracted from the best fit in a continuous set of renormalisation schemes. The fits are very good, with a � 2 per d.o.f smaller than 1. We propose a more stringent test of asymptotic scaling based on scheme in

Non-perturbative power corrections to ghost and gluon propagators

We study the dominant non-perturbative power corrections to the ghost and gluon propagators in Landau gauge pure Yang-Mills theory using OPE and lattice simulations. The leading order Wilson coefficients are proven to be the same for both propagators. The ratio of the ghost and gluon propagators is thus free from this dominant power correction. Indeed, a purely perturbative fit of this ratio gives smaller value ( 270MeV) of Λ than the one obtained from the propagators separately( 320MeV). This argues in favour of significant non-perturbative ~ 1/q2 power corrections in the ghost and gluon propagators. We check the self-consistency of the method.

Instantons and the A (2) condensate

We argue that the

Large momentum behavior of the ghost propagator in SU(3) lattice gauge theory

condensate found in the Landau gauge on lattices, when an Operator Product Expansion of Green functions is performed, might be explained by instantons. We use cooling to estimate the instanton contribution and extrapolate back the result to the thermalised configuration. The resulting

Preliminary Calculation of αS from Green Functions with Dynamical Quarks

is similar to

Constraints on the IR behaviour of gluon and ghost propagator from Ward-Slavnov-Taylor identities

.