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

Jan. 22, 2020, 4:15 p.m.
Adam Kwela (University of Gdańsk)
Haar-smallest sets
We will be interested in the following notions of smallness: a subset A of an abelian Polish group X is called Haar-countable/Haar-finite/Haar-n if there are a Borel set B containing A and a copy C …
Jan. 15, 2020, 4:15 p.m.
Michael Levin (Ben-Gurion University of the Negev, Israel)
Light maps of compacta
Based on a result of H. Torunczyk, R. Pol showed that a light map f: X->Y from a compactum X with dim X > 2 to a finite dimensional compactum Y is injective on a …
Jan. 8, 2020, 4:15 p.m.
Witold Marciszewski (University of Warsaw)
Countable dense homogeneous linear topological spaces
Recall that a topological space X is countable dense homogeneous (CDH) if X is separable, and given countable dense subsets D,E of X, there is an autohomeomorphism of X mapping D onto E. This is …
Dec. 18, 2019, 4:15 p.m.
Damian Sobota (Kurt Gödel Research Center, University of Vienna)
Convergence of measures in the random model
A Boolean algebra B has the Vitali--Hahn--Saks property if every sequence of measures on B which converges to 0 on elements of B converges also to 0 on every Borel subset of the Stone space …
Dec. 11, 2019, 4:15 p.m.
Piotr Szewczak (Cardinal Wyszyński University in Warsaw)
Null-additive sets and the property gamma
A subset X of the real line is null-additive if for each null set Y, the set X+Y is null. Under Martin Axiom, Galvin nad Miller constructed an uncountable null-additive set whose continuous images are …
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/ …