The commutative cohomology of two-generator semigroups
The second cohomology group \(H^2(S,A)\) classifies commutative group coextensions of \(S\) by \(A\). The paper under review deals with a simpler case, namely when \(A\) is thin and \(S\) is finite groupfree with two generators. In this case \(S\) has at most one noncyclic Ponizovskij factor. The author uses a general description of \(H^2(S,A)\) to investigate various particular cases and to study the relationship between the cohomology groups of \(S\) and its main Ponizovskij factor.
scientific article; zbMATH DE number 1394454