Using the theory of rudimentary recursion and provident sets developed in a previous paper, we give a treatment of set forcing appropriate for working over models of a theory PROVI which may plausibly claim to be the weakest set theory supporting a smooth theory of set forcing, and of which the minimal model is Jensen’s Jω. Much of the development is rudimentary or at worst given by rudimentary...

1. Introduction Let V [G] be the result of adding a Cohen real and a Cohen subset of ω 2 to a model V of the GCH. Every infinite cardinal gets a new subset in V [G], namely, the Cohen real. Yet, in some sense, only ω and ω 2 get new subsets. One way to capture this is to say that a sort of dual to Covering holds between V and V [G], namely, " κ-cocovering " for κ other than ω and ω 2. We need s...

With every σ-ideal I on a Polish space we associate the σ-ideal generated by closed sets in I. We study the forcing notions of Borel sets modulo the respective σ-ideals and find connections between their forcing properties. To this end, we associate to a σ-ideal on a Polish space an ideal on a countable set and show how forcing properties of the forcing depend on combinatorial properties of the...

We prove that a number of axioms, each a consequence of PFA (the Proper Forcing Axiom) are equivalent. In particular we show that TOP (the Thinning-out Principle as introduced by Baumgartner in the Handbook of set-theoretic topology), is equivalent to the following statement: If I is an ideal on co, with co, generators, then there exists an uncountable X C co,, such that either [X]w n I = 0 or ...

The Proper Forcing Axiom is a powerful extension of the Baire Category Theorem which has proved highly effective in settling mathematical statements which are independent of ZFC. In contrast to the Continuum Hypothesis, it eliminates a large number of the pathological constructions which can be carried out using additional axioms of set theory. Mathematics Subject Classification (2000). Primary...

We prove a variety of theorems about stationary set reflection and concepts related to internal approachability. that an implication Fuchino-Usuba relating version Strong Chang's Conjecture cannot be reversed; strengthen simplify some results Krueger forcing axioms approachability; other are sharp. also adapt ideas Woodin unify many arguments in the literature involving preservation axioms.

‎Let Γa be a graph whose each vertex is colored either white or black‎. ‎If u is a black vertex of Γ such that exactly one neighbor‎ ‎v of u is white‎, ‎then u changes the color of v to black‎. ‎A zero forcing set for a Γ graph is a subset of vertices Zsubseteq V(Γ) such that‎ if initially the vertices in Z are colored black and the remaining vertices are colored white‎, ‎then Z changes the col...