The finite presentation of the stable Hom functors, the Bass torsion, and the cotorsion coradical

Alex Martsinkovsky

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arXiv · 2212.09237

The finite presentation of the stable Hom functors, the Bass torsion, and the cotorsion coradical

Alex Martsinkovsky

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Abstract

We provide necessary and/or sufficient conditions for the stable Hom functors to be finitely presented. When the covariant Hom functor modulo projectives is finitely presented, its defect is isomorphic to the Bass torsion of the fixed argument. When the contravariant Hom functor modulo injectives is finitely presented, its defect is isomorphic to the cotorsion of the fixed argument. We also give a sufficient condition for the sub-stabilization of the tensor product to be finitely presented. A finite presentation of the tensor product leads to an unexpected application.

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Alex Martsinkovsky. 2022-12-19. The finite presentation of the stable Hom functors, the Bass torsion, and the cotorsion coradical. https://arxiv.org/abs/2212.09237

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