Between the classes of semi-Eberlein and Valdivia compact spaces

Speaker(s)

Maksymilian Wesoły

Affiliation

University of Warsaw

Language of the talk

Polish

Date

June 3, 2026, 4:15 p.m.

Room

room 4050

Seminar

Topology and Set Theory Seminar

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Recently Todorcevic has introduced the hierarchy of E_2(\theta) compact spaces. Motivated by the definition of Valdivia compact spaces, we introduce a corresponding hierarchy of semi-E_2(\theta) compacta. We investigate how these classes behave under Alexandroff duplicates. In particular, we show that if K is a compact space, then the Alexandroff duplicate of K is E_2(\theta) if and only if it is semi-E_2(\theta). This result yields examples distinguishing some of the classes in the hierarchy. It may also be considered a partial answer to a question posed by Kalenda. 
This is joint work with Antonio Avilés and Mikołaj Krupski. 

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