  By using the background field method of QCD in a path integral approach, we
derive the equation of motion for the classical chromofield and for the gluon
in a system containing the gluon and the classical chromofield simultaneously.
This inhomogeneous field equation contains a current term, which is the
expectation value of a composite operator including linear, square and cubic
terms of the gluon field. We also derive identities which the current should
obey from the gauge invariance. We calculate the current at the leading order
where the current induced by the gluon is opposite in sign to that induced by
the quark. This is just the feature of the non-Abelian gauge field theory which
has asymptotic freedom. Physically, the induced current can be treated as the
'displacement' current in the polarized vacuum, and its effect is equivalent to
redefining the field and the coupling constant.

High Energy Physics - Theory;High Energy Physics - Phenomenology