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Universal localizations embedded in power-series rings

  • Pere Ara EMAIL logo and Warren Dicks
Published/Copyright: March 12, 2007
Forum Mathematicum
From the journal Volume 19 Issue 2

Abstract

Let R be a ring, let F be a free group, and let X be a basis of F.

Let ε : RFR denote the usual augmentation map for the group ring RF, let X∂ := {x − 1 | xX} ⊆ RF, let Σ denote the set of matrices over RF that are sent to invertible matrices by ε, and let (RF−1 denote the universal localization of RF at Σ.

A classic result of Magnus and Fox gives an embedding of RF in the power-series ring R〈〈X∂〉〉. We show that if R is a commutative Bezout domain, then the division closure of the image of RF in R〈〈X∂〉〉 is a universal localization of RF at Σ.

We also show that if R is a von Neumann regular ring or a commutative Bezout domain, then (RF−1 is stably flat as an RF-ring, in the sense of Neeman-Ranicki.


(Communicated by Andrew Ranicki)


Received: 2006-01-29
Accepted: 2006-03-30
Published Online: 2007-03-12
Published in Print: 2007-03-20

© Walter de Gruyter

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