Organizers

prof. dr hab. Witold Marciszewski
prof. dr hab. Piotr Zakrzewski

Information

Wednesdays, 4:15 p.m. , room: 5050

Research fields

Topology and Set Theory

List of talks

June 8, 2016, 4:15 p.m.
Saeed Ghasemi (IMPAN)
Non-trivially isomorphic corona algebras
It is well-known that there are Cech-Stone remainders (corona spaces) of locally compact spaces for which the question of whether they are homeomorphic is independent from ZFC (e.g., the Cech-Stone remainders of the ordinals \omega …
June 1, 2016, 4:15 p.m.
Piotr Koszmider (IMPAN)
Scattered C*-algebras: A case study in noncommutative set-theoretic topology
The passage from commutative to noncommutative mathematics has stimulated a big part of mathematical research since the mid 20th century which resulted the unprecedented impact of this programme on the shape of today's mathematics. Quite …
May 25, 2016, 4:15 p.m.
Piotr Borodulin-Nadzieja (Uniwersytet Wrocławski)
Measures and slaloms
We construct several examples of spaces supporting measures using a technique developed by Todorcevic. In particular, we show that there is a ZFC example of non-separable growth of omega supporting a measure and that consistently …
May 11, 2016, 4:15 p.m.
Witold Marciszewski (Uniwersytet Warszawski)
On continuous images of compact spaces of finite sets
April 27, 2016, 4:15 p.m.
Wiesław Kubiś (Cardinal Stefan Wyszyński University in Warsaw)
Abstract Banach-Mazur game
We shall present a generalization of the Banach-Mazur game in the setting of partially ordered sets. This approach leads to significant simplifications of arguments showing uniqueness and universality of certain objects related to Fraisse limits. …
April 13, 2016, 4:15 p.m.
Tomasz Weiss (UKSW)
O translacjach zbioru domknietego miary zero w R
Opowiem o łatwiejszym przykładzie (pochodzącym od Elekesa i Totha) zbioru domkniętego miary zero w przestrzeni Cantora, którego mniej niż continuum translacji pokrywa całą przestrzeń. Przedstawię również ciekawy problem B.Tsabana dotyczący translacji zbioru domkniętego miary zero.
April 6, 2016, 4:15 p.m.
Todor Tsankov (Université Paris Diderot)
Metric Scott analysis
Back-and-forth equivalence relations have been an important tool in model theory and descriptive set theory since their advent in the fifties. They provide Borel approximations to the isomorphism relation that are useful in a variety …
March 16, 2016, 4:15 p.m.
Adam Kwela (Uniwersytet Gdański)
Ideałowe klasy Baire'a
Praca wspólna z Marcinem Staniszewskim. Zbadamy klasy Baire'a względem ideałowej e-zbieżności ("equal convergence" lub "quasi-normal convergence") generowane przez rodziny funkcji ciągłych i quasi-ciągłych. Przy okazji przypomnimy dotychczasowe wyniki z tej tematyki.
Feb. 3, 2016, 4:15 p.m.
Damian Sobota (doktorant IMPAN)
On families deciding Rosenthal's lemma
A classical version of Rosenthal's lemma reads as follows. Given a sequence (mu_k) of finitely additive bounded positive measures on P(N) and an infinite antichain (a_n) in P(N), for every epsilon > 0 there exists …
Jan. 27, 2016, 4:15 p.m.
Grzegorz Plebanek (Uniwersytet Wrocławski)
Uzwarcenia liczb naturalnych i przestrzeń Banacha c_0
Wraz z P. Drygierem badaliśmy, dla jakich uzwarceń \gammaN przestrzeni dyskretnej N naturalna kopia c_0 jest dopełnialna w C(\gammaN). W szczególności skonstruowaliśmy uzwarcenie z narostem ośrodkowym, które nie ma tej własności. Konstrukcja nie wymaga dodatkowych …
Jan. 13, 2016, 4:15 p.m.
Phillip Wesolek ( Université catholique de Louvain )
Chief factors in Polish groups
Abstract: (Joint work with Colin Reid.) For a Polish group G, closed normal subgroups L
Dec. 16, 2015, 4:15 p.m.
Piotr Zakrzewski (University of Warsaw)
Paradoxical decompositions into pieces with the Baire Property - continuation.
Dec. 9, 2015, 4:15 p.m.
Piotr Zakrzewski (University of Warsaw)
Paradoxical decompositions into pieces with the Baire Property
I will present the following theorem due to Andrew Marks and Spencer Unger: Suppose G is a group of Borel automorphisms of a Polish space X. Then if X has a G-paradoxical decomposition into arbitrary …
Dec. 2, 2015, 4:15 p.m.
Tomasz Weiss (Cardinal Stefan Wyszyński University in Warsaw)
On products of gamma sets - continuation from 4.11.2015
The presentation is based on the paper "Selective covering properties of product spaces, part 2,gamma spaces", preprint 2013, by A.Miller,B.Tsaban,L.Zdomsky.
Nov. 25, 2015, 4:15 p.m.
Rafał Filipów (The University of Gdańsk)
A critical ideal with respect to Mazurkiewicz's theorem in terms of the Katetov order
Consider a property of ideals: property(I). One can ask whether there is a critical ideal C for property(I) in terms of the Katetov order <_K i.e. property(I) <=> C <_K I. Many examples of critical …