The Mass of the 0 in selfdual QCD
The QCD gauge eld is modeled as an ensemble of statistically independent selfdual and antiselfdual regions. This model is motivated from instanton physics. The scale anomaly then allows to relate the topological susceptibility to the gluon condensate. With the help of Wittens formula for m 0 and an estimate of the suppression of the gluon condensate due to light quarks the mass of the 0 can be related to f and the physical gluon condensate. We get the quite satisfactory value m 0 = 884116 MeV. Using the physical 0 mass as an input it is in princple possible to get information about the interaction between instantons and anti-instantons.