The local composite operator A 2 µ is added to the Zwanziger action, which implements the restriction to the Gribov region Ω in Euclidean Yang-Mills theories in the Landau gauge. We prove that Zwanziger's action with the inclusion of the operator A 2 µ is renormalizable to all orders of perturbation theory, obeying the renormalization group equations. This allows to study the dimension two gluon condensate A 2 µ by the local composite operator formalism when the restriction to the Gribov region Ω is taken into account. The resulting effective action is evaluated at one-loop order in the MS scheme. We obtain explicit values for the Gribov parameter and for the mass parameter due to A 2 µ , but the expansion parameter turns out to be rather large. Furthermore, an optimization of the perturbative expansion in order to reduce the dependence on the renormalization scheme is performed. The properties of the vacuum energy, with or without the inclusion of the condensate A 2 µ , are investigated. In particular, it is shown that in the original Gribov-Zwanziger formulation, i.e. without the inclusion of the operator A 2 µ , the resulting vacuum energy is always positive at oneloop order, independently from the choice of the renormalization scheme and scale. In the presence of A 2 µ , we are unable to come to a definite conclusion at the order considered. In the MS scheme, we still find a positive vacuum energy, again with a relatively large expansion parameter, but there are renormalization schemes in which the vacuum energy is negative, albeit the dependence on the scheme itself appears to be strong. Concerning the behaviour of the gluon and ghost propagators, we recover the well known consequences of the restriction to the Gribov region, and this in the presence of A 2 µ , i.e. an infrared suppression of the gluon propagator and an enhancement of the ghost propagator. Such a behaviour is in qualitative agreement with the results obtained from the studies of the Schwinger-Dyson equations and from lattice simulations.

We investigate a dynamical mass generation mechanism for the off-diagonal gluons and ghosts in SUN Yang-Mills theories, quantized in the maximal Abelian gauge. Such a mass can be seen as evidence for the Abelian dominance in that gauge. It originates from the condensation of a mixed gluon-ghost operator of mass dimension two, which lowers the vacuum energy. We construct an effective potential for this operator by a combined use of the local composite operators technique with the algebraic renormalization and we discuss the gauge parameter independence of the results. We also show that it is possible to connect the vacuum energy, due to the mass dimension-two condensate discussed here, with the nontrivial vacuum energy originating from the condensate hA 2 i, which has attracted much attention in the Landau gauge.

We point out the existence of a non-perturbative exact nilpotent BRST symmetry for the Gribov-Zwanziger action in the Landau gauge. We then put forward a manifestly BRST invariant resolution of the Gribov gauge fixing ambiguity in the linear covariant gauge.

The nonlocal mass operator Tr R d 4 xF D 2 ÿ1 F is considered in Yang-Mills theories in Euclidean space-time. It is shown that the operator Tr R d 4 xF D 2 ÿ1 F can be cast in local form through the introduction of a set of additional fields. A local and polynomial action is thus identified. Its multiplicative renormalizability is proven by means of the algebraic renormalization in the class of linear covariant gauges. The anomalous dimensions of the fields and of the mass operator are computed at one-loop order. A few remarks on the possible role of this operator for the issue of the gauge invariance of the dimension two condensates are outlined.

We present a local setup for the recently introduced BRST-invariant formulation of Yang-Mills theories for linear covariant gauges that takes into account the existence of gauge copies \`a la Gribov and Zwanziger. Through the convenient use of auxiliary fields, including one of the Stueckelberg type, it is shown that both the action and the associated nilpotent BRST operator can be put in local form. Direct consequences of this fully local and BRST-symmetric framework are drawn from its Ward identities: (i) an exact prediction for the longitudinal part of the gluon propagator in linear covariant gauges that is compatible with recent lattice results and (ii) a proof of the gauge-parameter independence of all correlation functions of local BRST-invariant operators