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Co-stationarity of the ground model

Published online by Cambridge University Press:  12 March 2014

Natasha Dobrinen
Affiliation:
Kurt Gödel Research Center For Mathematical Logic, Universität Wien, Währingerstrasse 25, 1090 Wien, Austria.E-mail:dobrinen@logic.univie.ac.at, URL: http://www.logic.univie.ac.at/~dobrinen/
Sy-David Friedman
Affiliation:
Kurt Gödel Research Center For Mathematical Logic, Universität Wien, Währingerstrasse 25, 1090 Wien, Austria.E-mail:sdf@logic.univie.ac.at, URL: http://www.logic.univie.ac.at/~sdf/

Abstract

This paper investigates when it is possible for a partial ordering ℙ to force Pk(Λ)\V to be stationary in V. It follows from a result of Gitik that whenever ℙ adds a new real, then Pk(Λ)\V is stationary in V for each regular uncountable cardinal κ in V and all cardinals λ ≥ κ in V [4], However, a covering theorem of Magidor implies that when no new ω-sequences are added, large cardinals become necessary [7]. The following is equiconsistent with a proper class of ω1-Erdős cardinals: If ℙ is ℵ1-Cohen forcing, then Pk(Λ)\V is stationary in V, for all regular κ ≥ ℵ2and all λ ≩ κ. The following is equiconsistent with an ω1-Erdős cardinal: If ℙ is ℵ1-Cohen forcing, then is stationary in V. The following is equiconsistent with κ measurable cardinals: If ℙ is κ-Cohen forcing, then is stationary in V.

Type
Research Article
Copyright
Copyright © Association for Symbolic Logic 2006

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References

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