Abstract
We study when a union of saturated models is saturated in the framework of tame abstract elementary classes (AECs) with amalgamation. We prove:
Theorem 0.1. If K is a tame AEC with amalgamation satisfying a natural definition of superstability (which follows from categoricity in a high-enough cardinal), then for all high-enough \(\lambda {:}\)
-
(1)
The union of an increasing chain of \(\lambda \)-saturated models is \(\lambda \)-saturated.
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(2)
There exists a type-full good \(\lambda \) -frame with underlying class the saturated models of size \(\lambda \).
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(3)
There exists a unique limit model of size \(\lambda \).
Our proofs use independence calculus and a generalization of averages to this non first-order context.
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This material is based upon work done while Will Boney was supported by the National Science Foundation under Grant No. DMS-1402191 and Sebastien Vasey was supported by the Swiss National Science Foundation under Grant No. 155136.
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Boney, W., Vasey, S. Chains of saturated models in AECs. Arch. Math. Logic 56, 187–213 (2017). https://doi.org/10.1007/s00153-017-0532-0
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DOI: https://doi.org/10.1007/s00153-017-0532-0
Keywords
- Abstract elementary classes
- Forking
- Independence calculus
- Classification theory
- Stability
- Superstability
- Tameness
- Saturated models
- Limit models
- Averages
- Stability theory inside a model