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The torsionfree part of the Ziegler spectrum of RG when R is a Dedekind domain and G is a finite group

Published online by Cambridge University Press:  12 March 2014

A. Marcja
Affiliation:
Dipartimento Di Matematica, U. Dini, Università Di Firenze, Viale Morgagni 67/A, 1-50134 Firenze, Italy, E-mail: [email protected]
M. Prest
Affiliation:
Department of Mathematics, University of Manchester, Oxford Road, Manchester M13 9PL, England, E-mail: [email protected]
C. Toffalori
Affiliation:
Dipartimento Di Matematica E Infomatica, Università Di Camerino, Via Madonna Delle Carceri, 1-62032 Camerino, Italy, E-mail: [email protected]

Extract

For every ring S with identity, the (right) Ziegler spectrum of S, Zgs, is the set of (isomorphism classes of) indecomposable pure injective (right) S-modules. The Ziegler topology equips Zgs with the structure of a topological space. A typical basic open set in this topology is of the form

where φ and ψ are pp-formulas (with at most one free variable) in the first order language Ls for S-modules; let [φ/ψ] denote the closed set Zgs - (φ/ψ). There is an alternative way to introduce the Ziegler topology on Zgs. For every choice of two f.p. (finitely presented) S-modules A, B and an S-module homomorphism f: AB, consider the set (f) of the points N in Zgs such that some S-homomorphism h: AN does not factor through f. Take (f) as a basic open set. The resulting topology on Zgs is, again, the Ziegler topology.

The algebraic and model-theoretic relevance of the Ziegler topology is discussed in [Z], [P] and in many subsequent papers, including [P1], [P2] and [P3], for instance. Here we are interested in the Ziegler spectrum ZgRG of a group ring RG, where R is a Dedekind domain of characteristic 0 (for example R could be the ring Z of integers) and G is a finite group. In particular we deal with the R-torsionfree points of ZgRG.

The main motivation for this is the study of RG-lattices (i.e., finitely generated R-torsionfree RG-modules).

Type
Research Article
Copyright
Copyright © Association for Symbolic Logic 2002

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References

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