On matrix invertible extensions over commutative rings

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Hauptverfasser: Calugareanu, Grigore, Pop, Horia F., Vasiu, Adrian
Format: Preprint
Veröffentlicht: 2023
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author Calugareanu, Grigore
Pop, Horia F.
Vasiu, Adrian
author_facet Calugareanu, Grigore
Pop, Horia F.
Vasiu, Adrian
contents We introduce the class E2 (resp. SE2) of commutative rings R with the property that each unimodular 2 x 2 matrix with entries in R extends to an invertible 3 x 3 matrix (resp. invertible 3 x 3 matrix whose (3, 3) entry is 0). Among noetherian domains of dimension 1, polynomial rings over Z or Hermite rings, only EDRs belong to the class. Using this, stable ranges, and units and projective modules interpretations, we reobtain (often refine) criteria due to Kaplansky, McGovern, Roitman, Shchedryk, Wiegand and obtain new criteria for a Hermite ring to be an EDR. For instance, we characterize Hermite rings which are EDRs by (1) means of equations involving unimodular triples and (2) surjectivity of some maps involving units of factor rings by principal ideals. We use these criteria to show that each Bezout ring R that is either a J2,1 domain or an (SU)2 ring (as introduced by Lorenzini) such that for each nonzero a 2 R there exists no nontrivial self-dual projective R/Ra-module of rank 1 generated by 2 elements (e.g., all its elements are squares), is an EDR, thus solving or partially solving problems raised by Lorenzini. Many other classes of rings are introduced and studied. To ease the reading, this version concentrates only on extendability properties of unimodular 2 x 2 matrices and hence does not consider the case n > 2.
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id arxiv_https___arxiv_org_abs_2303_08413
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle On matrix invertible extensions over commutative rings
Calugareanu, Grigore
Pop, Horia F.
Vasiu, Adrian
Commutative Algebra
Rings and Algebras
Primary: 15A83, 13G05, 19B10. Secondary: 13A05, 13F05, 13F25, 15B33, 16U10, 16U30
We introduce the class E2 (resp. SE2) of commutative rings R with the property that each unimodular 2 x 2 matrix with entries in R extends to an invertible 3 x 3 matrix (resp. invertible 3 x 3 matrix whose (3, 3) entry is 0). Among noetherian domains of dimension 1, polynomial rings over Z or Hermite rings, only EDRs belong to the class. Using this, stable ranges, and units and projective modules interpretations, we reobtain (often refine) criteria due to Kaplansky, McGovern, Roitman, Shchedryk, Wiegand and obtain new criteria for a Hermite ring to be an EDR. For instance, we characterize Hermite rings which are EDRs by (1) means of equations involving unimodular triples and (2) surjectivity of some maps involving units of factor rings by principal ideals. We use these criteria to show that each Bezout ring R that is either a J2,1 domain or an (SU)2 ring (as introduced by Lorenzini) such that for each nonzero a 2 R there exists no nontrivial self-dual projective R/Ra-module of rank 1 generated by 2 elements (e.g., all its elements are squares), is an EDR, thus solving or partially solving problems raised by Lorenzini. Many other classes of rings are introduced and studied. To ease the reading, this version concentrates only on extendability properties of unimodular 2 x 2 matrices and hence does not consider the case n > 2.
title On matrix invertible extensions over commutative rings
topic Commutative Algebra
Rings and Algebras
Primary: 15A83, 13G05, 19B10. Secondary: 13A05, 13F05, 13F25, 15B33, 16U10, 16U30
url https://arxiv.org/abs/2303.08413