Ext for blocks with cyclic defect groups (Q798421)

The main result of this paper is the following: Let A be a k-algebra given by a Brauer tree with e edges and multiplicity m at the exceptional vertex. Let S be a fixed simple A-module whose projective cover is uniserial. Let i be an odd integer and j an even integer. Then there are m non-projective indecomposable A-modules M satisfying \(Ext^ n_ A(S,M)=k\) for \(n\equiv i(mod 2e)\), \(=k\) for \(n\equiv j(mod 2e)\), \(=0\) otherwise. Furthermore, these modules are described explicitly.