A Framework for Forcing Constructions at Successors of Singular Cardinals

Abstract

We describe a framework for proving consistency results about singular cardinals of arbitrary cofinality and their successors. This framework allows the construction of models in which the Singular Cardinals Hypothesis fails at a singular cardinal of uncountable cofinality, while its successor enjoys various combinatorial properties. As a sample application, we prove the consistency (relative to that of ZFC plus a supercompact cardinal) of there being a strong limit singular cardinal $\kappa$ of uncountable cofinality where SCH fails and for which there is a collection of graphs on $\kappa^+$ whose size is less than $2^\kappa$ and such that any graph on $\kappa^+$ embeds into one of the graphs in the collection.