I will introduce the definitions of Suslin ccc, Suslin proper and transitive nep, demonstrate that many of the usual "definable" forcings of sets of reals are Suslin; and present an application of these notions, a simplified version of Shelah's "preserving a little implies preserving much": If \(I\) is an ideal generated by a Suslin ccc forcing (e.g. null or meager), and \(P\) is a transitive nep forcing, and (in \(V\) and every forcing extension) \(P\) forces that no old positive Borel-set becomes null, then \(P\) forces that no old positive set becomes null.
Preserving non-null with transitive nep forcings
01.04.2003 15:00 - 16:30
Organiser:
KGRC
Location:
SR 101, 2. St., Währinger Str. 25