We give a characterization of extendibility in terms of embeddings between the structures H.. By that means, we show that the GCH can be forced (by a class forcing) while preserving extendible cardinals. As a corollary, we argue that such cardinals cannot in general be made indestructible by (set) forcing, under a wide variety of forcing notions.
机构:
Waseda Univ, Fac Sci & Engn, Shinjuku Ku, Okubo 3-4-1, Tokyo 1698555, JapanWaseda Univ, Fac Sci & Engn, Shinjuku Ku, Okubo 3-4-1, Tokyo 1698555, Japan
机构:
CUNY Bernard M Baruch Coll, Dept Math, New York, NY 10010 USA
CUNY, Grad Ctr, New York, NY 10016 USACUNY Bernard M Baruch Coll, Dept Math, New York, NY 10010 USA