In this paper A is a ring with
unit, and Mod-A denotes the category of unitary right A-modules. The aim of the
paper is to dualize the concept of torsion and develop the corresponding idea of
cotorsion.
One generalization of torsion was given by Goldman, using what he called a
kernel functor. These kernel functors are here dualized to give cokernel functors.
Cokernel functors are categorized over Mod-A.
The final section investigates what information the cotorsion functors can reveal about
the homological properties of the rings under discussion.
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