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On Representations of Orders Over Dedekind Domains

Published online by Cambridge University Press:  20 November 2018

D. G. Higman
D. G. Higman*
Affiliation:
University of Michigan
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We study representations of o-orders, that is, of o-regular -algebras, in the case that o is a Dedekind domain. Our main concern is with those -modules, called -representation modules, which are regular as o-modules. For any -module M we denote by D(M) the ideal consisting of the elements x ∈ o such that x.Ext1(M, N) = 0 for all -modules N, where Ext = Ext(,0) is the relative functor of Hochschild (5). To compute D(M) we need the small amount of homological algebra presented in § 1. In § 2 we show that the -representation modules with rational hulls isomorphic to direct sums of right ideal components of the rational hull A of , called principal-modules, are characterized by the property that D(M) ≠ 0. The (, o)-projective -modules are those with D(M) = 0. We observe that D(M) divides the ideal I() of (2) for every M , and give another proof of the fact that I() ≠ 0 if and only if A is separable. Up to this point, o can be taken to be an arbitrary integral domain.

Type
Research Article
Information
Canadian Journal of Mathematics , Volume 12 , 1960 , pp. 107 - 125
Copyright
Copyright © Canadian Mathematical Society 1960

References

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