A Framework for Forcing Constructions at Successors of Singular Cardinals
James Cummings, Mirna Džamonja, Menachem Magidor, Charles G. Morgan, Saharon Shelah
Abstract
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James Cummings, Mirna Džamonja, Menachem Magidor, Charles G. Morgan, Saharon Shelah
Abstract
Open-access reader
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 $κ$ of uncountable cofinality where SCH fails and for which there is a collection of graphs on $κ^+$ whose size is less than $2^κ$ and such that any graph on $κ^+$ embeds into one of the graphs in the collection.
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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 $κ$ of uncountable cofinality where SCH fails and for which there is a collection of graphs on $κ^+$ whose size is less than $2^κ$ and such that any graph on $κ^+$ embeds into one of the graphs in the collection.
Key concepts: Cofinality, Uncountable set, Mathematics, Regular cardinal, Successor cardinal, Consistency (knowledge bases), Discrete mathematics, Limit (mathematics)