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

March 10, 2021, 4:15 p.m.
Piotr Koszmider (Institute of Mathematics of the Polish Academy of Sciences)
A Banach space induced by an almost disjoint family, admitting only few operators and decompositions
We consider the closed linear subspace X(A) of the Banach space of real bounded sequences (l_infinity) generated by sequences converging to zero (c_0) and the characteristic functions of elements of an uncountable, almost disjoint family …
March 3, 2021, 4:15 p.m.
Marcin Sabok (McGill University)
Probabilistic programming semantics for name generation
Abstract: I will discuss a recent result connecting the nu-calculus (which is an extension of simply-typed lambda calculus modelling the so-called "name generation") with a recent model for probabilistic programming, called the quasi-Borel spaces. There …
- slides
Jan. 27, 2021, 4:15 p.m.
Aleksandra Kwiatkowska (University of Wrocław)
The automorphism group of the random poset
A number of well-studied properties of Polish groups concern the interactions between the topological and algebraic structure of those groups. Examples of such properties are the small index property, the automatic continuity, and the Bergman …
- slides
Jan. 20, 2021, 4:15 p.m.
Adam Bartoš (Institute of Mathematics of the Czech Academy of Sciences)
Approximate Fraïssé theory and MU-categories
Fraïssé theory links together properties of families of structures like the amalgamation property with properties of limit objects like homogeneity and the extension property. The structures considered are not limited to be first-order structures, and …
- slides
Jan. 13, 2021, 4:15 p.m.
Rafał Filipów (University of Gdańsk)
If I were a rich density
Abstract upper densities are monotone and subadditive functions from the power set of positive integers into the unit real interval that generalize the upper densities used in number theory, including the upper asymptotic density, the …
- notes from the talk
Dec. 16, 2020, 4:15 p.m.
Wiesław Kubiś (Cardinal Stefan Wyszyński University in Warsaw and Institute of Mathematics of the Czech Academy of Sciences)
The weak Ramsey property
We show how to extend the Kechris-Pestov-Todorcevic correspondence to categories with weak amalgamations, where extreme amenability is tested for the automorphism group of the generic limit, taken with a suitable topology. We characterize extreme amenability …
- slides
Dec. 9, 2020, 4:15 p.m.
Antonio Aviles Lopez (Universidad de Murcia)
The category of Banach lattices
We shall review some recent developments in the study of the category of Banach lattices: Free, projective, injective objects, etc. Analogies and differences with Banach spaces will be highlighted. This is part of joint works …
- links to a related article
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 …
- file
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 …
- file
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 …
- file
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 …