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

Dec. 4, 2019, 4:15 p.m.
Szymon Głąb (Institute of Mathematics Technical University of Łódź)
joint project with Stefan Geschke and Wiesław Kubiś (Inverse limits of finite graphs)
The random graph R is the unique countable graph which contains isomorphic copies of all countable graphs and is homogeneous in the sense that every isomorphism between its finite subgraphs extends to an automorphism of …
Nov. 27, 2019, 4:15 p.m.
Grzegorz Plebanek (University of Wrocław)
Monolithic spaces of measures
For a compact space K, we consider the space P(K) of regular probability measures on K, equipped with the weak* topology. For zerodimensional spaces K, we can, equvalently, speak of P(A), the space of finitely …
Nov. 6, 2019, 4:15 p.m.
Piotr Zakrzewski (University of Warsaw)
On Mazurkiewicz's sets and regularity properties of sigma-ideals
The talk will present results from a joint paper with Roman Pol. Let f:X --> Y be a continuous surjection of the compact metrizable space X onto an uncountable compact metrizable space Y. A Mazurkiewicz …
Oct. 31, 2019, 4:15 p.m.
Arturo Antonio Martínez Celis Rodríguez (IMPAN)
Cardinal Invariants and Rosenthal families
Rosenthal's lemma is a classical result that concerns sequences of measures on pairwise disjoint sets and a Rosenthal family is a collection of infinite subsets of the natural numbers that can replace the collection of …
Oct. 23, 2019, 4:15 p.m.
Roman Pol (University of Warsaw)
On uniformly tight sets of probability measures on the rationals
The talk will present results obtained jointly with Piotr Zakrzewski. Let P(Q) be the space of probability measures on the rationals Q, equipped with the weak topology. A set A in P(Q) is uniformly …
Oct. 16, 2019, 4:15 p.m.
Mikołaj Krupski (University of Warsaw)
Hereditarily Baire hyperspaces, filters and spaces of measures - part 2
This part does not depend on the material presented under the same title during the first part of the talk. A topological space X is Baire if the intersection of a countable family of open …
Oct. 9, 2019, 4:15 p.m.
Mikołaj Krupski (University of Warsaw)
Hereditarily Baire hyperspaces, filters and spaces of measures
A topological space X is Baire if the intersection of a countable family of open dense sets in X is dense. We say that X is hereditarily Baire if every closed subspace of X is …
June 12, 2019, 4:15 p.m.
Mikołaj Krupski (University of Warsaw)
Embedding of the Free Abelian Topological Group A(X x X) into A(X)
In my talk I will discuss the following question: For which separable metrizable spaces X does the free abelian topological group A(X x X) isomorphically embed into A(X)? While for many natural spaces X such …
June 5, 2019, 4:15 p.m.
Piotr Koszmider (IMPAN)
On R-embeddability of almost disjoint families and some problems concerning C*-algebras
An almost disjoint family A of subsets of N is said to be R-embeddable if there is a function f:N→R such that the sets f[A] are ranges of real sequences converging to distinct reals for …
May 29, 2019, 4:15 p.m.
Tomasz Weiss (Cardinal Wyszyński University in Warsaw)
Some properties of the * operation on families of special subsets of R. Algebraic sum of a perfect set and large subsets of R
In the first part of this talk I will present the following lemma. Assume CH. Given a non trivial ideal F of subsets of R which is Borel supported, translation invariant, with cov(F) =c/the continuum/ …
May 22, 2019, 4:15 p.m.
Tomasz Cieśla (McGill University)
Measurable Hall's theorem for actions of abelian groups
We prove a measurable version of the Hall marriage theorem for actions of finitely generated abelian groups. In particular, it implies that for free measure-preserving actions of such groups, if two equidistributed measurable sets are …
May 15, 2019, 4:15 p.m.
Witold Marciszewski (University of Warsaw)
Twist and Shout - a continuation
We consider the class of Banach spaces Y for which the space c_0 admits a nontrivial twisted sum with Y, i.e., there exists a Banach space X containing a noncomplemented copy Z of c_0 such …
May 8, 2019, 4:15 p.m.
Witold Marciszewski (University of Warsaw)
Twist and Shout
We consider the class of Banach spaces Y for which the space c_0 admits a nontrivial twisted sum with Y, i.e., there exists a Banach space X containing a noncomplemented copy Z of c_0 such …
April 17, 2019, 4:15 p.m.
Damian Sobota (Kurt Gödel Research Center, University of Vienna)
Selected topics in convergence of measures on compact spaces
During my talk I'll present some most recent results of my joint work with Lyubomyr Zdomskyy concerning different aspects of convergence of sequences of Radon measures on compact spaces. Among others, I'll present a (sketch …
April 10, 2019, 4:15 p.m.
Rafał Górak (Warsaw University of Technology)
A classification of spaces of continuous functions on ordinals
During my talk, I will present the missing case of the topological classification of spaces of continuous real-valued functions Cp([0, \aplha]) on ordinals. This result was recently presented by Genze, Gulko and Khymyleva (https://arxiv.org/pdf/1806.09015.pdf) and …