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

Oct. 10, 2018, 4:15 p.m.
Viktoriia Brydun (Lviv National University)
Fuzzy metrization of the spaces of idempotent measures
The talk will be dedicated to idempotent mathematics (better known as tropical mathematics) and category theory. The idempotent measures (Maslov measures) are counterparts of the probability measures in the idempotent mathematics. The main result …
June 13, 2018, 4:15 p.m.
Kazimierz Alster (UKSW)
Gra Telgarskiego a multiplikatywność parazwartości
Ogólnym problemem dotyczącym multiplikatywności parazwartości jest pytanie o charakteryzację klasy P przestrzeni parazwartych, których iloczyn kartezjański z dowolną przestrzenią parazwartą jest parazwarty a także związane z nim problemy: Czy klasa P jest zamknięta ze względu …
June 6, 2018, 4:15 p.m.
Piotr Szewczak (Cardinal Stefan Wyszyński University in Warsaw)
Products of Luzin-type sets with combinatorial properties
A topological space is Menger if for any sequence U1, U2, … of open covers of the space, there are finite subsets F1, F2, … of U1, U2, …, respectively, such that the union of …
May 23, 2018, 4:15 p.m.
Kazimierz Alster (UKSW)
Gra Telgarskiego a multiplikatywność parazwartości
Ogólnym problemem dotyczącym multiplikatywności parazwartości jest pytanie o charakteryzację klasy P przestrzeni parazwartych, których iloczyn kartezjański z dowolną przestrzenią parazwartą jest parazwarty a także związane z nim problemy: Czy klasa P jest zamknięta ze względu …
May 16, 2018, 4:15 p.m.
Julien Melleray (Institut Camille Jordan, Université Lyon 1)
Full groups of minimal homeomorphisms of the Cantor space
The first part of the talk will be an introduction to the theory of minimal homeomorphisms and their full groups (and why these objects are interesting). In the second talk I'll sketch the proof of …
May 9, 2018, 4:15 p.m.
Rafał Filipów (University of Gdańsk)
Ideal convergence versus matrix summability
Ideal convergence and matrix summability are examples of extensions of the ordinary convergence of sequences of reals to a larger class of sequences (i.e. ordinary convergent sequences remain convergent to the same limits and there …
April 25, 2018, 4:15 p.m.
Andrzej Szymański (Cardinal Stefan Wyszyński University in Warsaw)
KKM Theorem: From L*-operators to a Renting Problem
- The abstract of the talk
April 11, 2018, 4:15 p.m.
Roman Pol (University of Warsaw)
On a paper by M.V.Ferrer, S.Hernandez and D.Shakhmatov "A countable free closed non-reflexive subgroup of Z^continuum", Proc.AMS 145(2017).
An abelian topological group H is (Pontrjagin) reflexive if the natural homomorphism from H into the group H^^ of characters on the group of characters on H is a homeomorphism of H onto H^^ (as …
March 21, 2018, 4:15 p.m.
Piotr Szewczak (Cardinal Stefan Wyszyński University in Warsaw)
The Haar measure problem
An old problem asks whether every compact group has a Haar-nonmeasurable subgroup. A series of earlier results reduce the problem to infinite metrizable profinite groups. We provide a positive answer, assuming a weak, potentially provable, …
March 14, 2018, 4:15 p.m.
Ralf Schindler (Department for Mathematical Logic and Foundational Research, University of Munster)
"Paradoxical" sets with no well-ordering of the reals
By a Hamel basis we mean a basis for the reals, R, construed as a vecor space over the field of rationals. In 1905, G. Hamel constructed such a basis from a well-ordering of R. …
March 7, 2018, 4:15 p.m.
Witold Marciszewski (University of Warsaw)
On zero-dimensional subspaces of Eberlein compacta
Let us recall that a compact space K is Eberlein compact if it can be embedded into some Banach space X equipped with the weak topology. We will discuss the following problem: Does every nonmetrizable …
Feb. 28, 2018, 4:15 p.m.
TOMASZ NATKANIEC (University of Gdańsk)
PERFECTLY EVERYWHERE SURJECTIVE BUT NOT JONES FUNCTIONS
Given a function f : R → R we say that • f is perfectly surjective (f ∈ PES) if f[P] = R for every perfect set P; • f is a Jones function (f …
Jan. 24, 2018, 4:15 p.m.
Taras Banakh (Lviv National University and UJK Kielce)
Null-finite sets in metric groups and their applications
We shall introduce a new family of "small" sets which is tightly connected with two well known $\sigma$-ideals: of Haar-null sets and of Haar-meager sets. We define a subset $A$ of a topological group $X$ …
Jan. 17, 2018, 4:15 p.m.
Szymon Żeberski (Wrocław University of Technology)
Nonmeasurable sets and unions with respect to tree ideals
We consider a notion of nonmeasurablity with respect to Marczewski and Marczewski-like tree ideals $s_0$, $m_0$, $l_0$, and $cl_0$. We show that there exists a subset $A$ of the Baire space $\omega^\omega$ which is $s$-, …
Dec. 20, 2017, 4:15 p.m.
Damian Sobota (Kurt Gödel Research Center for Mathematical Logic)
Convergence of measures and cardinal characteristics of the continuum
Let A be a Boolean algebra. We say that A has the Nikodym property if every pointwise convergent sequence of measures on A is weak* convergent. Similarly, A has the Grothendieck property if every weak* …