Donder's Version of Revised Countable Support

Revised support iterations and CH

Shelah shows that certain revised countable support (RCS) iterations do not add reals. His motivation is to establish the independence (relative to large cardinals) of Avraham's problem on the existence of uncountable non-constuctible sequences all of whose proper initial segments are constructible, Friedman's problem on whether every 2-coloring of $S^2_0=\{α<ω_2\colon\cf(α)=ω\}$ has an uncountable sequentially closed homogeneous subset, and existence of a precipitous normal filter on $ω_2$ with $S^2_0\in{\cal F}$. The posets which Shelah uses in these constructions are Prikry forcing, Namba f…

More on forcing iteration

The preservation theorems for semi-properness, hemi-properness, and pseudo-completeness hold for countable support iterations as well as revised countable support iterations, notwithstanding the fact that the "factor lemma" fails for the countable support versions. Example: The countable support iteration of Namba forcing over a ground model of CH does not add reals. Example: A countable support iteration built from Namba forcing and Cohen forcing, over a ground model of CH, does not collapse omega_1

力迫类子版本的迭代定理

Iteration theorems for subversions of forcing classes

针对Jensen提出的子真和子完全力迫相关类，证明了修正可数支撑迭代下三类子真力迫的可迭代性，还通过宫本良迭代理论去掉子完全/子真性的技术条件，仍保可迭代性等性质并推广类似定理。