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IDEAL PROJECTIONS AND FORCING PROJECTIONS

Published online by Cambridge University Press:  12 December 2014

SEAN COX
Affiliation:
DEPARTMENT OF MATHEMATICS AND APPLIED MATHEMATICS VIRGINIA COMMONWEALTH UNIVERSITY 1015 FLOYD AVENUE RICHMOND, VIRGINIA 23284, USAE-mail: scox9@vcu.edu
MARTIN ZEMAN
Affiliation:
DEPARTMENT OF MATHEMATICS 340 ROWLAND HALL UNIVERSITY OF CALIFORNIA, IRVINE IRVINE, CA 92697-3875, USAE-mail: mzeman@math.uci.edu
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Abstract

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It is well known that saturation of ideals is closely related to the “antichain-catching” phenomenon from Foreman–Magidor–Shelah [10]. We consider several antichain-catching properties that are weaker than saturation, and prove:

  1. (1) If ${\cal I}$ is a normal ideal on $\omega _2 $ which satisfies stationary antichain catching, then there is an inner model with a Woodin cardinal;

  2. (2) For any $n \in \omega $, it is consistent relative to large cardinals that there is a normal ideal ${\cal I}$ on $\omega _n $ which satisfies projective antichain catching, yet ${\cal I}$ is not saturated (or even strong). This provides a negative answer to Open Question number 13 from Foreman’s chapter in the Handbook of Set Theory ([7]).

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Copyright © The Association for Symbolic Logic 2014