English

In the situation of finite dimensional modules over tame quiver algebras the degeneration-order coincides with the hom-order and with the ext-order. Therefore, up to common direct summands, any minimal degeneration N of a module M is induced by a short exact sequence with middleterm M and indecomposable ends U and V that add up to N. We study these "building blocs" of degenerations and in particular the codimensions for the case, where V is regular. We show by theoretical means that the classification of all the "building blocs" is a finite problem without affecting the codimension or the type of singularity. With the help of a computer we have analyzed completely this case: The codimensions are bounded by 2, so that the minimal singularities are known by G. Zwara "Codimensions two singularities for representation of extended dynkin quivers".