  Concerning the trace anomaly in field theory a nonvanishing vacuum energy
breaks the scale symmetry as well, in addition to the usual beta function
dependent term, requiring a unit operator in the trace anomaly. This additional
term is also necessary in quantum chromodynamics (QCD) to cancel the inherent
ambiguity in the gluon condensate. The inseparability of the gluon condensate
effect from the perturbative contribution to the vacuum energy renders it
impossible to isolate the gluon condensate effect on the cosmological constant.
