Rigid Ideals

02.03.2017 15:00 - 16:30

B. M. Cody (Virginia Commonwealth U, Richmond, US)

An ideal \(I\) on a cardinal \(\kappa\) is called rigid if all automorphisms of \(P(\kappa)/I\) are trivial. Woodin proved that if \(MA_{\omega_1}\) holds, then every saturated ideal on \(\omega_1\) is rigid. In all previously known models containing rigid saturated ideals, GCH fails. In this talk I will discuss recent joint work with Monroe Eskew in which we prove that the existence of a rigid saturated ideal on \(\mu^+\), where \(\mu\) , where \(\mu\) is an uncountable regular cardinal, is consistent with GCH, relative to the existence of an almost huge cardinal. Our proof involves adapting the Friedman-Magidor coding forcing (from the number of normal measures paper) to code a generic for a universal collapsing poset which forces an almost huge cardinal \(\kappa\) to become the successor of an uncountable regular \(\mu\). Our forcing is \({<}\mu\)-distributive and in the resulting forcing extension, GCH holds and there is a saturated ideal \(I\) on \(\mu^+\) such that in any forcing extension by \(\mathbb{P}=P(\mu^+)/I\) there is a unique generic filter for \(\mathbb{P}\), hence \(I\) is rigid.

Organiser:

KGRC

Location:
SR 101, 2. St., Währinger Str. 25