Dynamical quarks effects on the gluon propagation and chiral symmetry restoration

We exploit the recent lattice results for the infrared gluon propagator with light dynamical quarks and solve the gap equation for the quark propagator. Chiral symmetry breaking and confinement (intimately tied with the analytic properties of QCD Schwinger functions) order parameters are then studied.

A novel method for the physical scale setting on the lattice and its application to $N_f$=4 simulations

This letter reports on a new procedure for the lattice spacing setting that takes advantage of the very precise determination of the strong coupling in Taylor scheme. Although it can be applied for the physical scale setting with the experimental value of $Lambda_{overline{rm MS}}$ as an input, the procedure is particularly appropriate for relative calibrations. The method is here applied for simulations with four degenerate light quarks in the sea and leads to prove that their physical scale is compatible with the same one for simulations with two light and two heavy flavours.

Three-gluon running coupling from lattice QCD at $N_f=2+1+1$: a consistency check of the OPE approach

We present a lattice calculation of the renormalized running coupling constant in symmetric (MOM) and asymmetric ($widetilde{rm MOM}$) momentum substraction schemes including $u$, $d$, $s$ and $c$ quarks in the sea. An Operator Product Expansion dominated by the dimension-two $langle A^2rangle$ condensate is used to fit the running of the coupling. We argue that the agreement in the predicted $langle A^2rangle$ condensate for both schemes is a strong support for the validity of the OPE approach and the effect of this non-gauge invariant condensate over the running of the strong coupling.

Testing the OPE Wilson coefficient for $A^2$ from lattice QCD with a dynamical charm

Gluon and ghost propagators data, obtained in Landau gauge from lattice simulations with two light and two heavy dynamical quark flavours ($N_f$=2+1+1), are described here with a running formula including a four-loop perturbative expression and a nonperturbative OPE correction dominated by the local operator $A^2$. The Wilson coefficients and their variation as a function of the coupling constant are extracted from the numerical data and compared with the theoretical expressions that, after being properly renormalized, are known at ${cal O}(alpha^4)$. As also $Lambda_{msbar}$ is rather well known for $N_f$=2+1+1, this allows for a precise consistency test of the OPE approach in the joint description of different observables.