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THE SOLIDITY AND NONSOLIDITY OF INITIAL SEGMENTS OF THE CORE MODEL

Published online by Cambridge University Press:  23 October 2018

GUNTER FUCHS
Affiliation:
MATHEMATICS, THE GRADUATE CENTER OF THE CITY UNIVERSITY OF NEW YORK 365 FIFTH AVENUE, NEW YORK, NY 10016, USA and MATHEMATICS, COLLEGE OF STATEN ISLAND OF CUNY STATEN ISLAND, NY 10314, USAE-mail:gunter.fuchs@csi.cuny.eduURL: http://www.math.csi.cuny/edu/∼fuchs
RALF SCHINDLER
Affiliation:
INSTITUT FÜR MATHEMATISCHE LOGIK UND GRUNDLAGENFORSCHUNG UNIVERSITÄT MÜNSTER EINSTEINSTR. 62, 48149 MÜNSTER, GERMANYE-mail:rds@math.uni-muenster.deURL: https://ivv5hpp.uni-muenster.de/u/rds/

Abstract

It is shown that $K|{\omega _1}$ need not be solid in the sense previously introduced by the authors: it is consistent that there is no inner model with a Woodin cardinal yet there is an inner model W and a Cohen real x over W such that $K|{\omega _1}\,\, \in \,\,W[x] \setminus W$. However, if ${0^{\rm{\P}}}$ does not exist and $\kappa \ge {\omega _2}$ is a cardinal, then $K|\kappa$ is solid. We draw the conclusion that solidity is not forcing absolute in general, and that under the assumption of $\neg {0^{\rm{\P}}}$, the core model is contained in the solid core, previously introduced by the authors.

It is also shown, assuming ${0^{\rm{\P}}}$ does not exist, that if there is a forcing that preserves ${\omega _1}$, forces that every real has a sharp, and increases $\delta _2^1$, then ${\omega _1}$ is measurable in K.

Type
Articles
Copyright
Copyright © The Association for Symbolic Logic 2018 

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References

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