Peter Jorgensen

  1. Triangulated categories of extensions and the Second Isomorphism Theorem for triangulated categories.

    Authors: Kiriko Kato, Peter Jorgensen
    Subjects: Representation Theory
    Abstract

    Let T be a triangulated category with triangulated subcategories X and Y. We
    show that the subcategory of extensions X * Y is triangulated if and only if Y
    * X is contained in X * Y.

    In this situation, we show the following analogue of the Second Isomorphism
    Theorem: (X * Y) / X is equivalent to Y / (X \cap Y) and (X * Y) / Y is
    equivalent to X / (X \cap Y).

  2. Symmetric Auslander and Bass categories.

    Authors: Kiriko Kato, Peter Jorgensen
    Subjects: Commutative Algebra
    Abstract

    We define the symmetric Auslander category A^s(R) to consist of complexes of
    projective modules whose left- and right-tails are equal to the left- and right
    tails of totally acyclic complexes of projective modules.

    The symmetric Auslander category contains A(R), the ordinary Auslander
    category. It is well known that A(R) is intimately related to Gorenstein
    projective modules, and our main result is that A^s(R) is similarly related to
    what can reasonably be called Gorenstein projective homomorphisms. Namely,
    there is an equivalence of triangulated categories:

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