Few new reals

Abstract

We introduce a new method for building models of CH, together with ${\Pi }_2$ statements over $H({\omega }_2)$, by forcing. Unlike other forcing constructions in the literature, our construction adds new reals, although only ${\aleph }_1$-many of them. Using this approach, we build a model in which a very strong form of the negation of Club Guessing at ${\omega }_1$ known as Measuring holds together with CH, thereby answering a well-known question of Moore. This construction can be described as a finite-support weak forcing iteration with side conditions consisting of suitable graphs of sets of models with markers. The CH-preservation is accomplished through the imposition of copying constraints on the information carried by the condition, as dictated by the edges in the graph.

arXiv comment39 pages