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A downward Löwenheim-Skolem theorem for infinitary theories which have the unsuperstability property

Published online by Cambridge University Press:  12 March 2014

Rami Grossberg*
Affiliation:
Department of Mathematics, Rutgers University, New Brunswick, New Jersey 08903

Abstract

We present a downward Löwenheim-Skolem theorem which transfers downward formulas from L∞,ω to , ω. The simplest instance is:

Theorem 1. Let λ > κ be infinite cardinals, and let L be a similarity type of cardinality κ at most. For every L-structure M of cardinality λ and every XM there exists a model N ≺ M containing the set X of powerX∣ · κ such that for every pair of finite sequences a, b ∈ N

The following theorem is an application:

Theorem 2. Let λ<κ, T, ω, and suppose χ is a Ramsey cardinal greater than λ. If T has the (χ, , ω)-unsuperstability property, then T has the (χ, , ω)-unsuperstability property.

Type
Research Article
Copyright
Copyright © Association for Symbolic Logic 1988

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Footnotes

1

I would like to thank John Baldwin for asking me a question which is the reason why I wrote this paper, and for his valuable remarks on the first draft. This research was partially supported by NSF grant DMS-8603167.

References

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