A study of fermionic three-point vertex with gluon condensate

We derive the dimension-four gluon condensate contributions to the fermionic three-point vertex with different forms of the gluon condensate component of the nonlocal two-gluon vacuum expectation value (vev). We find that the result with the non-covariant form of nonlocal two-gluon vev in the fixed-point gauge depends on whether the zero-point is set on the fermionic- or gluonic-line. But this uncertainty can be avoided by using the covariant form of the nonlocal two-gluon vev.