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. 2, 2020, 4:15 p.m.
Piotr Szewczak (Cardinal Stefan Wyszyński University in Warsaw)
Abstract colorings, games and ultrafilters
During the talk we consider various kinds of Ramsey-type theorems. Bergelson and Hindman investigated finite colorings of the complete graph [N]^2 with vertices in natural numbers, involving an algebraic structure of N. It follows from …
- slides
Nov. 25, 2020, 4:15 p.m.
Jan van Mill (University of Amsterdam)
Modal logic for topologists
We sketch the proof of the following result: the existence of a normal space whose modal logic coincides with the modal logic of the Kripke frame isomorphic to the power set of a two element …
- slides
Nov. 18, 2020, 4:15 p.m.
Lyubomyr Zdomskyy (Institut für Mathematik, Kurt Gödel Research Center, Universität Wien)
Between the Pytkeev and Frechet-Urysohn properties of function spaces
In this talk we aim to compare the Frechet-Urysohn property and some of its formal weakenings for spaces of the form C_p(X). In particular, we plan to present a sketch of the construction under CH …
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Nov. 4, 2020, 4:15 p.m.
Maciej Malicki (IMPAN)
Non-locally compact Polish groups and non-essentially countable orbit equivalence relations
It is a long-standing open question whether every Polish group that is not locally compact admits a Borel action on a standard Borel space whose associated orbit equivalence relation is not essentially countable. In the …
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Oct. 28, 2020, 4:15 p.m.
Taras Banakh (Ivan Franko National University of Lviv and UJK Kielce)
Small uncountable cardinals in asymptology
In the talk we shall discuss some cardinal characteristics of the continuum that appear in large-scale topology, usually as the smallest weights of coarse structures that belong to certain classes (indiscrete, inseparable, large) of finitary …
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March 11, 2020, 4:15 p.m.
Ziemowit Kostana (University of Warsaw)
Cohen-like poset for adding automorphisms of Fraisse limits
There exists a natural forcing notion which turns the set of integers into a Fraisse limit of a given Fraisse class. This long-known phenomenon provided a rough intuition that Fraisse limits, as "generic structures", have …
March 4, 2020, 4:15 p.m.
Witold Marciszewski (University of Warsaw)
X\times Y), sequences of measures, and ultrafilter (Complemented subspaces of function spaces C_p)
The result of Schachermayer and Cembranos asserts that, for a compact space K, the Banach space C(K) of continuous real valued maps on K, contains a complemented copy of the Banach space c_0 if and …
Feb. 26, 2020, 4:15 p.m.
Piotr Borodulin-Nadzieja (University of Wrocław)
Analytic P-ideals and Banach spaces
I will talk about certain symmetries between analytic P-ideals and Banach spaces with unconditional bases (e.g. I will give some examples of Banach spaces motivated by ideals and vice-versa). I will present a theorem saying …
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 …