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

Nov. 16, 2022, 4:15 p.m.
Lyubomyr Zdomskyy (Technische Universität Wien)
On cardinalities of Lindelöf first countable spaces
We shall present the main ideas of the construction of a Lindelöf first countable T_1 space of cardinality bigger than continuum. This is a modification of an earlier construction invented by Gorelic. It is well-known …
- slides
Nov. 9, 2022, 4:15 p.m.
Mikołaj Krupski (University of Warsaw)
\kappa-pseudocompactness and uniform homeomorphisms of function spaces
A Tychonoff space X is called \kappa-pseudocompact if for every continuous mapping f of X into R^\kappa the image f(X) is compact. This notion generalizes pseudocompactness and gives a stratification of spaces lying between pseudocompact …
Oct. 26, 2022, 4:15 p.m.
Maciej Malicki (IM PAN)
Isomorphism of locally compact Polish metric structures
Gao and Kechris asked if the isometry relation on the space of locally compact Polish metric spaces is (Borel) reducible to the isomorphism relation of countable graphs. It turns out that this question is easier …
Oct. 19, 2022, 4:15 p.m.
Paweł Krupski (Wrocław University of Science and Technology)
On the hyperspace of simple closed curves in the plane
The Vietoris hyperspace of simple closed curves in the plane will be discussed. Its characterization is a challenging open problem. An elementary proof of the hyperspace's local contractibility will be presented. Joint work with Krzysztof Omiljanowski. ----------------------------------------------------- …
June 8, 2022, 4:15 p.m.
Wiesław Kubiś (Institute of Mathematics of the Czech Academy of Sciences and Cardinal Stefan Wyszyński University in Warsaw)
Homogeneity of linear spaces
Linear spaces are basic incidence structures consisting of points and lines, These are in fact first order structures naturally encoded by a single ternary relation. We shall discuss homogeneity questions, namely, when every small partial …
June 1, 2022, 4:15 p.m.
Mikołaj Krupski (University of Warsaw)
Preservation of some covering type properties by linear homeomorphisms of function spaces: Part 2
In the second part of my talk I will show some proof techniques. The talk should be accessible regardless of listening to part 1. An old question of Arhangel'skii asks if (a) the Lindelof property …
May 25, 2022, 4:15 p.m.
Mikołaj Krupski (University of Warsaw)
Preservation of some covering type properties by linear homeomorphisms of function spaces
An old question of Arhangel'skii asks if (a) the Lindelof property (b) the Menger property of a Tychonoff space X is preserved by homeomorphisms of the space C_p(X) of continuous functions on X equipped with …
May 18, 2022, 4:15 p.m.
Damian Głodkowski (University of Warsaw)
K) reading the dimension of (A Banach space C)
We show that if Jensen's diamond principle holds, then for every natural number n there is a compact space K, such that whenever L is compact space and the Banach spaces of continuous functions C(K) …
May 11, 2022, 4:15 p.m.
Tomasz Cieśla (Lancaster University)
On random compact sets, equidecomposition and domains of expanison in R^3
We describe a certain model of random compact sets. We use it to construct a pair of compact sets A and B in R^3 of the same Lebesgue measure such that A can be covered …
April 27, 2022, 4:15 p.m.
Ziemowit Kostana (Bar-Ilan University)
Playing games with diamonds
Parametrized diamonds are combinatorial principles that imply many consequences of the original Jensen's Diamond, yet are consistent with the CH failing. Informally speaking, they are in similar relation to Jensen's Diamond, as cardinal invariants of …
April 6, 2022, 4:15 p.m.
Antonio Aviles Lopez (Universidad de Murcia)
Topological properties in tensor products of Banach spaces
We will expose a recent work with G. Martinez Cervantes, J. Rodriguez and A. Rueda Zoca where we study several topological properties (like weakly compactly generated, weakly Lindelöf determined, property (C) of Corson...) on tensor …
- slides
March 30, 2022, 4:15 p.m.
Robert Rałowski (University of Wrocław)
Mycielski among trees
The two-dimensional version of Mycielski theorem says that for every comeager or conull subset G of the real plane there exists a perfect subset of the real line such that the square of this perfect …
March 23, 2022, 4:15 p.m.
Piotr Szewczak (Cardinal Stefan Wyszyński University in Warsaw)
Strongly sequentially separable function spaces
A space is Frechet–Urysohn if each point in the closure of a set is a limit of a sequence from the set. A separable space is strongly sequentially separable if, for each countable dense set, …
March 16, 2022, 4:15 p.m.
Piotr Koszmider (IM PAN)
Almost disjoint families and the geometry of spheres
We present an example of a nonseparable Banach space where every uncountable subset of the unit sphere contains two vectors which are distant by less than one. This solves in the negative the central problem …
Jan. 26, 2022, 4:15 p.m.
Taras Banakh (Ivan Franko National University of Lviv and UJK Kielce)
Automatic continuity of measurable homomorphisms on topological groups
We shall discuss three recent results on automatic continuity of homomorphisms: 1) Every Haar-measurable homomorphism from a locally compact group to an arbitrary topological group is continuous. 2) Every homomorphism with the Baire property from …
- slides