An r-fold analogue of the positive semidefinite zero forcing process that is carried out on the r-blowup of a graph is introduced and used to define the fractional positive semidefinite forcing number. Properties of the graph blowup when colored with a fractional positive semidefinite forcing set are examined and used to define a three-color forcing game that directly computes the fractional po...

In an Appalachian Set Theory Workshop [3], Gitik presented some of the details of a simplified version of the poset from his original paper. The discussion there motivates the definition of the forcing by modifying a poset which requires a stronger large cardinal assumption which is sometimes called the long extender forcing. However, the discussion recorded in the Appalachian Set Theory (AST) ...

We define and investigate HC-forcing invariant formulas of set theory, whose interpretations in the hereditarily countable sets are well behaved under forcing extensions. This leads naturally to a notion of cardinality ||Φ|| for sentences Φ of Lω1,ω, which counts the number of sentences of L∞,ω that, in some forcing extension, become a canonical Scott sentence of a model of Φ. We show this card...

If T has only countably many complete types, yet has a type of infinite multiplicity then there is a c.c.c. forcing notion Q such that, in any Q-generic extension of the universe, there are non-isomorphic models M1 and M2 of T that can be forced isomorphic by a c.c.c. forcing. We give examples showing that the hypothesis on the number of complete types is necessary and what happens if ‘c.c.c.’ ...

We define and investigate HC-forcing invariant formulas of set theory, whose interpretations in the hereditarily countable sets are well behaved under forcing extensions. This leads naturally to a notion of cardinality ||Φ|| for sentences Φ of Lω1,ω, which counts the number of sentences of L∞,ω that, in some forcing extension, become a canonical Scott sentence of a model of Φ. We show this card...