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On the Dimension of Modules and Algebras, IV: Dimension of Residue Rings of Hereditary Rings

Published online by Cambridge University Press:  22 January 2016

Samuel Eilenberg
Affiliation:
Columbia University
Hirosi Nagao
Affiliation:
Osaka City University
Tadasi Nakayama
Affiliation:
Nagoya University
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A ring (with unit element) Λ is called semi-primary if it contains a nilpotent two-sided ideal N such that the residue ring Γ = Λ/N is semi-simple (i.e. l.gl.dim Γ = r.gl.dim Γ = 0). N is then the (Jacobson) radical of Λ. Auslander [1] has shown that if Λ is semi-primary then

The common value is denoted by gl. dim Λ. On the other hand, for any ring Λ the following conditions are equivalent : (a) 1. gl. dim Λ ≦ 1, (b) each left ideal in Λ is projective, (c) every submodule of a projective left Λ-module is projective. Rings satisfying conditions (a)-(c) are called hereditary. For integral domains the notions of “hereditary ring” and “Dedekind ring” coincide.

Type
Research Article
Copyright
Copyright © Editorial Board of Nagoya Mathematical Journal 1956

References

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