QCD effective action with a most general homogeneous field background

We consider one-loop effective action of SU(3) QCD with a most general constant chromomagnetic (chromoelectric) background which has two independent Abelian field components. The effective potential with a pure magnetic background has a local minimum only when two Abelian components H-mu nu(3) and H-mu nu(8) of color magnetic field are orthogonal to each other. The nontrivial structure of the effective action has important implication in estimating quark-gluon production rate and PT-distribution in quark-gluon plasma. In general the production rate depends on three independent Casimir invariants, in particular, it depends on the relative orientation between chromoelectric fields.