Gauge (in)dependence and background field formalism

It is shown that the gauge invariance and gauge dependence properties of effective action for Yang-Mills theories should be considered as two independent issues in the background field formalism. Application of this formalism to formulate the functional renormalization group approach is discussed. It is proven that there is a possibility to construct the corresponding average effective action invariant under the gauge transformations of background vector field. Nevertheless, being gauge invariant this action remains gauge dependent on-shell.Comment: 14 pages, v2: typos corrected, v3:minor correction in Eqs. (2.24), v4: a reference added, misprints corrected, accepted for publication in PL

Gribov horizon beyond the Landau gauge

Gribov and Zwanziger proposed a modification of Yang-Mills theory in order to cure the Gribov copy problem. We employ field-dependent BRST transformations to generalize the Gribov-Zwanziger model from the Landau gauge to general R_xi gauges. The Gribov horizon functional is presented in explicit form, in both the non-local and local variants. Finally, we show how to reach any given gauge from the Landau one.Comment: 1+6 pages; v2: one ref. and 3 clarifications added, published versio

Representation of a gauge field via intrinsic "BRST" operator

We show that there exists a representation of a matrix valued gauge field via intrinsic "BRST" operator assigned to matrix valued generators of a gauge algebra. In this way, we reproduce the standard formulation of the ordinary Yang - Mills theory. In the case of a generating quasigroup/groupoid, we give a natural counterpart to the Yang - Mills action. The latter counterpart does also apply as to the most general case of an involution for matrix-valued gauge generators.Comment: 15 pages, no figures, Section 6 extended with (6.14), (6.15); v3: Section 7 added, minor corrections; v4: Section 4, minor corrections; v5: formula (4.11) modifie