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On infinite MacWilliams rings and minimal injectivity conditions
Journal article   Open access   Peer reviewed

On infinite MacWilliams rings and minimal injectivity conditions

Miodrag Cristian Iovanov
Proceedings of the American Mathematical Society, Vol.150(11), p.4575
11/01/2022
DOI: 10.1090/proc/15929
url
https://doi.org/10.1090/proc/15929View
Published (Version of record) Open Access

Abstract

We provide a complete answer to the problem of characterizing left Artinian rings which satisfy the (left or right) MacWilliams extension theorem for linear codes, generalizing results of Iovanov [J. Pure Appl. Algebra 220 (2016), pp. 560–576] and Schneider and Zumbrägel [Proc. Amer. Math. Soc. 147 (2019), pp. 947–961] and answering the question of Schneider and Zumbragel [Proc. Amer. Math. Soc. 147 (2019), pp. 947–961]. We show that they are quasi-Frobenius rings, and are precisely the rings which are a product of a finite Frobenius ring and an infinite quasi-Frobenius ring with no non-trivial finite modules (quotients). For this, we give a more general “minimal test for injectivity” for a left Artinian ring A: we show that if every injective morphism \Sigma _k\rightarrow A from the k’th socle of A extends to a morphism A\rightarrow A, then the ring is quasi-Frobenius. We also give a general result under which if injective maps N\rightarrow M from submodules N of a module M extend to endomorphisms of M (pseudo-injectivity), then all such morphisms N\rightarrow M extend (quasi-injectivity) and obtain further applications.
MacWilliams theorem finite ring quasi-injective Linear codes quasi-Frobenius pseudo-injective QF ring

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