Friday, December 4, 201510:00 amSet theory seminarGC 3212

Jónsson cardinals and club guessing

Shehzad Ahmed

Ohio University

Shehzad Ahmed

We say that a cardinal $\lambda$ is a Jónsson cardinal if it satisfies the following weak Ramsey-type property: given any coloring $F:[\lambda]^{<\omega}\to \lambda$ of the finite subsets of $\lambda$ in $\lambda$-many colors, there exists a set $H\in[\lambda]^\lambda$ such that the range of $F\upharpoonright [H]^{<\omega}$ is a proper subset of $\lambda$. One of the big driving forces present in early chapters Cardinal Arithmetic is an attempt to understand the combinatorial structure at and around Jónsson cardinals using scales and club guessing. The goal of this talk is to highlight the connection between Jónsson cardinals and the existence of certain sorts of club guessing ideals. Our focus will be on how club guessing ideals interact with Jónssonness at successors of singulars.

Shehzad Ahmed is a PhD student at Ohio University studying set theory under the supervision of Dr. Todd Eisworth.