Integrating out Gluons in Flow Equations
  We present an exact nonperturbative flow equation for the average action for quarks which incorporates the effects of gluon fluctuations. With suitable truncations this allows one to compute effective multiquark interactions in dependence on an infrared scale $k$. Our method amounts to integrating out the gluons with momenta larger than $k$. 
Christof Wetterich