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Elimination of quantifiers for ordered valuation rings
Published online by Cambridge University Press: 12 March 2014
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Cherlin and Dickmann [2] proved that the theory RCVR of real closed (valuation) rings admits quantifier-elimination (q.e.) in the language ℒ = {+, −, ·, 0, 1, <, ∣} for ordered rings augmented by the divisibility relation “∣”. The purpose of this paper is to prove a form of converse of this result:
Theorem. Let T be a theory of ordered commutative domains (which are not fields), formulated in the language ℒ. In addition we assume that:
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(1) The symbol “∣” is interpreted as the honest divisibility relation:
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(2) The following divisibility property holds in T:
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If T admits q.e. in ℒ, then T = RCVR.
We do not know at present whether the restriction imposed by condition (2) can be weakened.
The divisibility property (DP) has been considered in the context of ordered valued fields; see [4] for example. It also appears in [2], and has been further studied in Becker [1] from the point of view of model theory. Ordered domains in which (DP) holds are called in [1] convexly ordered valuation rings, for reasons which the proposition below makes clear. The following summarizes the basic properties of these rings:
Proposition I [2, Lemma 4]. (1) Let A be a linearly ordered commutative domain. The following are equivalent:
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(a) A is a convexly ordered valuation ring.
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(b) Every ideal (or, equivalently, principal ideal) is convex in A.
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(c) A is a valuation ring convex in its field of fractions quot(A).
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(d) A is a valuation ring and its maximal ideal MA is convex (in A or, equivalently, in quot (A)).
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(e) A is a valuation ring and its maximal ideal is bounded by ± 1.
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- Copyright © Association for Symbolic Logic 1987
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