Taking into account different tensor structures approximately corresponds to a sum of contributions $\simeq \sum_i \alpha_i^2$, if we denote the running couplings associated to different components of the quark-gluon vertex as $\alpha_i$ and neglect cross terms, whereas the enhanced vertex from the single channel approximation contributes as the square of the sums $\simeq (\sum_i\alpha_i )^2$ in the four-fermi box diagram.

Finally, we briefly discuss the mechanism of chiral symmetry breaking which is at work in our framework. Here, chiral symmetry breaking is driven by four-fermi interactions. In a framework of dynamical hadronisation this is reflected in the corresponding contributions to the Yukawa coupling/quark mass. Therefore, our calculation requires significantly less vertex strength in the quark-gluon vertex in order to see chiral symmetry breaking compared to the required strength in single channel approximation as described above. In our framework, including just the classical tensor structure in the quark-gluon vertex leads to qualitatively albeit not quantitatively correct results. This is mainly due to the contributions from the tensor structure $\tfrac{1}{2}{\cal
  T}^{(5)}_{\bar q A q}+{\cal T}^{(7)}_{\bar q A q}$ in the quark-gluon vertex and its gauge invariant completion, see the discussion in Sec. \[sec:quark\] and App. \[trunc:qprqglmom\].

Summary and conclusions
=======================

In the 