-Definability of the non-stationary ideal at successor cardinals
Volume 229 / 2015
Fundamenta Mathematicae 229 (2015), 231-254
MSC: Primary 03E35, 03E20; Secondary 03E45.
DOI: 10.4064/fm229-3-2
Abstract
Assuming V=L, for every successor cardinal \kappa we construct a GCH and cardinal preserving forcing poset \mathbb {P}\in L such that in L^{\mathbb {P}} the ideal of all non-stationary subsets of \kappa is \Delta _1-definable over H(\kappa ^{+}).
