Seminarium:
Topologia
Osoba referująca:
David Chodounsky (Czech Academy of Sciences)
Data:
wtorek, 24. Maj 2022 - 17:00
Sala:
601
Opis:
Preservation of reaping families and especially ultrafilters on countable
sets is a well studied theme in set theory of the reals. A. Miller proved
that if an ultrafilter remains a reaping family in some forcing extension,
then it has to be also Sacks indestructible. The existence of Sacks
indestructible ultrafilters in ZFC is an open question. A related problem
is Sacks indestructibility of reaping families which are complements of
ideals. We prove that complements of most classical ideals are
indestructible with one notable exception, the ideal of sets asymptotic
density zero. The presented results are from an upcoming paper with O.
Guzman and M. Hrusak.
About 15 minutes before the seminar we invite you for coffee and a chat.