Shelah's three cardinal and model-existence claims
Let be an ordinal, and let . For a countable theory , let a -like model mean a model of cardinality in the sense used in the source. Let .
Shelah's three cardinal and model-existence claims. The following assertions hold:
A)
B) If has a -like model, is a limit cardinal, and for a singular cardinal , then has a -like model. If is an -Mahlo weakly inaccessible cardinal, the stated cardinal and singularity restrictions on can be removed.
C) If has a model of cardinality , then it has a model of cardinality .
These are two-cardinal, partition, and model-existence assertions from Shelah's work. The source flags the last assertion with a reference to [Sh:522], so its status and the precise interpretation of the notation should be checked against that reference.
References
Primary source
Saharon Shelah, “A collection of abstracts of Shelah's Papers”, arXiv:2209.01617 (2022).
Additional references
2 papers in this index state this conjecture (2005–2022). The statement above is taken from the most recent of them; the others are arXiv:math/0509707.
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