The ‘BRST-invariant’ condensate of dimension two in QCD

The status of the ‘BRST-invariant’ condensate of mass dimension two in QCD is explained. The condensate is only invariant under an ‘on-shell’ BRST symmetry which includes a partial gauge fixing. The on-shell BRST symmetry represents the residual gauge symmetry under gauge transformations which preserve the partial gauge fixing. The gauge-invariant operators which correspond to the BRST-invariant condensate are identified in the Lorentz and maximal Abelian gauges and are shown to be invariant under the residual gauge transformations.