The singularities of Yang-Mills connections for bundles on a surface.
We prove: For a local analytic family of analytic space germs there is a largest subspace in such that the family is trivial over . Moreover the reduction of equals the germ of those points in for which is isomorphic to the special fibre .
We show that certain moduli spaces of vector bundles over blown-up primary Hopf surfaces admit no compact components. These are the moduli spaces used by Andrei Teleman in his work on the classification of class VII surfaces.