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In this paper we classify the the epimorphisms of irreducible spherical Moufang buildings (of rank at least 2) defined over a field. As an application we characterize indecomposable epimorphisms of these buildings as those epimorphisms arising from R-buildings., Comment: revised version, 44 pages

In this paper it is established that all two-dimensional polynomial automorphisms over a regular ring R are stably tame. In the case R is a Dedekind Q-algebra, some stronger results are obtained. A key element in the proof is a theorem which yields the following corollary: Over an Artinian ring A all two-dimensional polynomial automorphisms having Jacobian determinant one are stably tame, and are tame if A is a Q-algebra. Another crucial ingredient, of interest in itself, is that stable tameness is a local property: If an automorphism is locally tame, then it is stably tame., 18 pages

A GR segment of an Artin algebra is a sequence of Gabriel–Roiter measures that is closed under direct successors and direct predecessors. The number of GR segments was conjectured to relate to the representation types of finite-dimensional hereditary algebras. We prove in the paper that a path algebra K Q of a finite connected acyclic quiver Q over an algebraically closed field K is of wild representation type if and only if K Q admits infinitely many GR segments.