Abstract
A remarkable result by Shelah states that if κ is a singular strong limit cardinal of uncountable cofinality, then there is a subset x of κ such that HODx contains the power set of κ. We develop a version of diagonal extender-based supercompact Prikry forcing, and use it to show that singular cardinals of countable cofinality do not in general have this property, and in fact it is consistent that for some singular strong limit cardinal κ of countable cofinality κ+ is supercompact in HODx for all x ⊆ κ.
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Cummings was partially supported by the National Science Foundation, grants DMS-1101156 and DMS-1500790.
Friedman would like to thank the Austrian Science Fund for its generous support through the research project P25748.
Rinot was partially supported by the Israel Science Foundation, grant 1630/14.
Sinapova was partially supported by the National Science Foundation, grants DMS-1362485 and Career-1454945.
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Cummings, J., Friedman, SD., Magidor, M. et al. Ordinal definable subsets of singular cardinals. Isr. J. Math. 226, 781–804 (2018). https://doi.org/10.1007/s11856-018-1712-2
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DOI: https://doi.org/10.1007/s11856-018-1712-2