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Cancellation and stability properties of generalized torsion modules. (English) Zbl 1484.16002

Let \(R\) be a ring and \(M, M'\) be arbitrary \(R\)-modules. Recall that the cancellation problem for any \(R\)-module \(N\) asks, if \(M \oplus N \cong M' \oplus N\) implies \(M \cong M'\). The scope of this paper is a restriction of the cancellation problem to finitely generated \(R\)-modules and modification of the statement to finding all modules \(M'\) that satisfy for any positive integers \(a,b\), \(M \oplus R^a \cong M' \oplus R^b\) implies \(M \cong M'\). The isomorphism classes of such modules \(M'\) is called the stability class of \(M\) and denoted by \([M]\). This paper considers the tree structure on \([M]\) when \(M\) is a finitely generated module over a weakly finite ring \(R\). First, the paper studies the tree structure on \([0]\) and further proves that if \(M\) is also a generalized torsion module then the tree structure on \([0]\) and \([M]\) are isomorphic. Last section provides examples of group rings and application of the previous results to modules over these group rings and compares the results to the current literature.

MSC:

16D70 Structure and classification for modules, bimodules and ideals (except as in 16Gxx), direct sum decomposition and cancellation in associative algebras)
16S90 Torsion theories; radicals on module categories (associative algebraic aspects)
20E06 Free products of groups, free products with amalgamation, Higman-Neumann-Neumann extensions, and generalizations

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