Naredni sastanak Seminara biće održan u petak, 11. jula 2025. godine, u sali 301f Matematičkog instituta SANU sa početkom u 14.15. U pitanju je zajednički sastanak sa Seminarom za logiku.
Predavač: Justin Moore, Cornell University
Naslov predavanja: UNIFORM ULTRAFILTERS ON ω₁ AND THEIR COMPLEXITY
Apstrakt: This talk will investigate uniform ultrafilters on ω₁, both with respect to the Tukey order and the Rudin-Kiesler order. We show that it is independent of ZFC (modulo a large cardinal assumption) that every uniform ultrafilters on ω₁ has the maximum Tukey-type. We also show that PFA implies that Todorcevic’s ultrafilter 𝒰(T) has the maximum Tukey type of a directed set of cardinality 2^ℵ₁. We also show that PFA implies that 𝒰(T) is minimal in the Rudin-Kiesler order with respect to being a uniform ultrafilter on ω₁ and that it admits a finest partition. This is joint work with Tom Benhamou and Luke Serafin.
Napomena: Predavanje je moguće pratiti na daljinu putem linka
https://miteam.mi.sanu.ac.rs/asset/WbsehnSL4ZeTPJo6r
