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Paper   IPM / M / 17875
School of Mathematics
  Title:   The radical of functorially finite subcategories
  Author(s):  Alireza Nasr-Isfahani (Joint with R. Diyanatnezhad)
  Status:   Published
  Journal: J. Algebra
  Vol.:  657
  Year:  2024
  Pages:   675-703
  Supported by:  IPM
  Abstract:
Let Λ be an artin algebra and C be a functorially finite subcategory of modΛwhich contains Λor DΛ. We use the concept of the infinite radical of C and show that Chas an additive generator if and only if rad∞Cvanishes. In this case, we describe the morphisms in powers of the radical of C in terms of its irreducible morphisms. Moreover, under a mild assumption, we prove that C is of finite representation type if and only if any family of monomorphisms (epimorphisms) between indecomposable objects in Cis noetherian (conoetherian). Also, by using injective envelopes, projective covers, left C-approximations and right C-approximations of simple Λ-modules, we give other criteria to describe whether C is of finite representation type. In addition, we give a nilpotency index of the radical of C which is independent from the maximal length of indecomposable Λ-modules in C.

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