Organizers

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

Information

Wednesdays, 4:15 p.m. , room: 4050

Research fields

Topology and Set Theory

List of talks

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 …
Nov. 18, 2015, 4:15 p.m.
Taras Banakh (Lviv National University and UJK Kielce)
The closed Steinhaus properties of $σ$-ideals on topological groups
Abstract: We prove that any meager quasi-analytic subgroup of a topological group $G$ belongs to every $\sigma$-ideal $\mathcal I$ on $G$ possessing the closed ±n-Steinhaus property for some $n∈\mathbb N$. An ideal I on a …
Nov. 4, 2015, 4:15 p.m.
Tomasz Weiss (Cardinal Stefan Wyszyński University in Warsaw)
On products of gamma sets
I will present the following theorem due to Miller, Tsaban and Zdomsky:It is consistent with ZFC that there are two gamma sets whose cartesian product is not a Menger set. This result answers in the …
Oct. 21, 2015, 4:15 p.m.
Michał Korch (doktorant UW)
Generalised Egorov’s Statement for ideals
Tomasz Weiss has proven that the statement obtained from the classic Egorov's Theorem by dropping the measurability assumption (so called generalised Egorov's statement) is independent from ZFC (we restrict our attention to real functions). We …
Oct. 14, 2015, 4:15 p.m.
Piotr Szewczak; Coauthor: Boaz Tsaban (Bar-Ilan University, Israel) (Cardinal Stefan Wyszyński University in Warsaw)
Products of Menger spaces
A topological space X is Menger if for every sequence of open covers O_1, O_2, . . . there are ﬁnite subfamilies F_1 of O_1, F_2 of O_2, . . . such that their union …
Oct. 7, 2015, 4:15 p.m.
Maciej Malicki (Warsaw School of Economics)
Polish groups with ample generics and analytic P-ideals
A Polish group has ample generics if all its diagonal conjugation actions have a comeager orbit. This property has a number of interesting implications, e.g. automatic continuity of homomorphisms into separable groups. Until recently, all …
June 17, 2015, 4:15 p.m.
Brice Mbombo (Sao Paulo)
Ramsey properties for finite dimensional normed spaces
June 10, 2015, 4:15 p.m.
Piotr Koszmider (IMPAN)
Uncountable equilateral sets in Banach spaces
A set A in a Banach space X is said to be equilateral if there is a real r such that the distance between any two distinct elements of A is r. We construct the …
May 27, 2015, 4:15 p.m.
Damian Sobota (doktorant IMPAN)
Small Boolean algebras with the Nikodym property
Let A be a Boolean algebra. A sequence of measures (mu_n) on A is: * pointwise bounded if the sequence (|mu_n(a)|) is bounded for every a in A; * uniformly bounded if the sequence (||mu_n||) …
May 20, 2015, 4:15 p.m.
Grzegorz Plebanek (Uniwersytet Wrocławski)
Converging sequences of measures and complemented copies of c_0
If K is an infinite compact space then the Banach space C(K) contains natural copies of c_0. The question whether a given copy of c_0 is complemented in C(K) can be expressed in terms of …
May 13, 2015, 4:15 p.m.
Marcin Sabok (IMPAN)
Classification problems in symbolic dynamics
During this talk I will discuss the descriptive set-theoreticcomplexity of the topological conjugacy relation for free minimalG-subshifts for various countable groups G. For residually finite countablegroups G we will see that there exists a probability …
May 6, 2015, 4:15 p.m.
Marta Frankowska (Uniwersytet Gdański)
The density topology in the Cantor space
We consider some properties of ideal (a) defined on 2^{\omega} by classical density topology. We also discuss the possibility of using the Cantor function to prove analogous results on R.