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Generalized quantifiers and elementary extensions of countable models

Published online by Cambridge University Press:  12 March 2014

Małgorzata Dubiel*
Affiliation:
University of Warsaw, 00–901 Warsaw, Poland

Extract

Let L be a countable first-order language and L(Q) be obtained by adjoining an additional quantifier Q. Q is a generalization of the quantifier “there exists uncountably many x such that…” which was introduced by Mostowski in [4]. The logic of this latter quantifier was formalized by Keisler in [2]. Krivine and McAloon [3] considered quantifiers satisfying some but not all of Keisler's axioms. They called a formula φ(x) countable-like if

for every ψ. In Keisler's logic, φ(x) being countable-like is the same as ℳ⊨┐Qxφ(x). The main theorem of [3] states that any countable model ℳ of L[Q] has an elementary extension N, which preserves countable-like formulas but no others, such that the only sets definable in both N and M are those defined by formulas countable-like in M. Suppose C(x) in M is linearly ordered and noncountable-like but with countable-like proper segments. Then in N, C will have new elements greater than all “old” elements but no least new element — otherwise it will be definable in both models. The natural question is whether it is possible to use generalized quantifiers to extend models elementarily in such a way that a noncountable-like formula C will have a minimal new element. There are models and formulas for which it is not possible. For example let M be obtained from a minimal transitive model of ZFC by letting Qxφ(x) mean “there are arbitrarily large ordinals satisfying φ”.

Type
Research Article
Copyright
Copyright © Association for Symbolic Logic 1977

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References

REFERENCES

[1]Hutchinson, J. E., Elementary extensions of countable models of set theory, this Journal, vol. 41 (1976), pp. 139145.Google Scholar
[2]Keisler, H. J., Logic with the quantifier “there exist uncountably many”, Annals of Mathematical Logic, vol. 1 (1970), pp. 193.CrossRefGoogle Scholar
[3]Krivine, J. L. and McAloon, K., Forcing and generalized quantifiers, Annals of Mathematical Logic, vol. 5 (1973), pp. 199255.CrossRefGoogle Scholar
[4]Mostowski, A., On a generalization of quantifiers, Fundamenta Malhematicae, vol. 65 (1968), pp. 8393.CrossRefGoogle Scholar
[5]Solovay, R. M., Real-valued measurable cardinals, Axiomatic set theory, Proceedings of Symposia in Pure Mathematics, vol. 13, Part 1, edited by the American Mathematical Society, Providence, Rhode Island, 1971, pp. 397428.CrossRefGoogle Scholar