Organizatorzy

prof. dr hab. Witold Marciszewski
prof. dr hab. Piotr Zakrzewski

Informacje

środy, 16:15 , sala: 5050

Dziedziny badań

Topologia i teoria mnogości

Lista referatów

13 grudnia 2017 16:15
Tomasz Cieśla (University of Warsaw)
Homeomorphism relation of locally connected continua is complete
Every Borel action of a Polish group G on a Polish space X gives rise to a relation ~ given by x ~ y if and only if x and y are in the same …
29 listopada 2017 16:15
Ziemowit Kostana (University of Warsaw)
Non-measurability of the algebraic sums of sets of real numbers
Consider the following problems: 1. If A is a meagre (null) subset of the real line, does there necessarily exist a set B such that the algebraic sum A+B doesn't have the Baire property (is …
22 listopada 2017 16:15
Maciej Malicki (Warsaw School of Economics)
Generic representations of countable groups - part 2
The fact that a Polish group G has a comeager conjugacy class can be expressed in the language of representations: it is equivalent to the existence of a generic representation of the group of integers …
15 listopada 2017 16:15
Maciej Malicki (Warsaw School of Economics)
Generic representations of countable groups
The fact that a Polish group G has a comeager conjugacy class can be expressed in the language of representations: it is equivalent to the existence of a generic representation of the group of integers …
8 listopada 2017 16:15
Yurii Khomskii (Hamburg University)
Definable Maximal Independent Families
Maximal independent families are combinatorial objects that have applications in various areas of mathematics. A maximal independent family can be constructed using the Axiom of Choice, and an old result of Arnold Miller shows that …
25 października 2017 16:15
Marek Balcerzak (Politechnika Łódzka)
The Baire category of ideal convergent subseries and rearrangements of a divergent series
Let I be a 1-shift-invariant ideal on N with the Baire property. Assume that a series with terms in a real Banach space X is not unconditionally convergent. We show that the sets of I-convergent …
18 października 2017 16:15
Michał Korch (UW)
Specjalne podzbiory uogólnionej przestrzeni Cantora II / Special subsets of the generalized Cantor space II
Streszczenie: Mój referat zacznie się od wprowadzenia uogólnionej przestrzeni Cantora 2^\kappa dla regularnej nieprzeliczalnej liczby kardynalnej \kappa. Przestrzeń ta wyposażona jest w tak zwaną ograniczoną topologię, generowaną przez zbiory wszystkich przedłużeń funkcji częściowych. W ostatnich …
11 października 2017 16:15
Michał Korch (UW)
Specjalne podzbiory uogólnionej przestrzeni Cantora / Special subsets of the generalized Cantor space
Streszczenie: Mój referat zacznie się od wprowadzenia uogólnionej przestrzeni Cantora 2^\kappa dla regularnej nieprzeliczalnej liczby kardynalnej \kappa. Przestrzeń ta wyposażona jest w tak zwaną ograniczoną topologię, generowaną przez zbiory wszystkich przedłużeń funkcji częściowych. W ostatnich …
7 czerwca 2017 16:15
Jarosław Swaczyna (Łódź University of Technology)
Haar-like smallness in Polish groups
In locally compact Polish groups there is a very natural $\sigma$-ideal of null sets with respect to Haar-measure. In non locally compact groups there is no Haar measure, however Christensen introduced a notion of Haar-null …
31 maja 2017 16:15
Piotr Szewczak (Cardinal Stefan Wyszyński University in Warsaw)
The Scheepers property and products of Menger spaces
A topological space X is Menger if for every sequence of open covers O_1, O_2,... of the space X, there are ﬁnite subfamilies F_1\subseteq O_1, F_2\subseteq O_2,... such that their union is a cover of …
24 maja 2017 16:15
Piotr Koszmider (Institute of Mathematics of the Polish Academy of Sciences)
A nonseparable scattered C*-algebra without nonseparable commutative subalgebras
The talk is based on the paper T. Bice, P. Koszmider, A note on the Akemann-Doner and Farah-Wofsey constructions, PAMS 145 (2017), no. 2, 681–687, where we remove the continuum hypothesis from the previous construction …
17 maja 2017 16:15
Tomasz Cieśla (University of Warsaw)
Borel circle squaring - part 3
In 1925 Alfred Tarski asked whether a square is equidecomposable by isometries with a disc of the same area. This question was answered in the affirmative in 1990 by Laczkovich. In 2015 Grabowski, Mathe and …
10 maja 2017 16:15
Tomasz Cieśla (University of Warsaw)
Borel circle squaring - part 2
In 1925 Alfred Tarski asked whether a square is equidecomposable by isometries with a disc of the same area. This question was answered in the affirmative in 1990 by Laczkovich. In 2015 Grabowski, Mathe and …
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26 kwietnia 2017 16:15
Witold Marciszewski (University of Warsaw)
Extension operators and twisted sums - part 3.
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29 marca 2017 16:15
Martin Dolezal (University of Warsaw)
Sigma-porosity and infinite games
We introduce an infinite game characterizing various types of sigma-porosity for Souslin sets in terms of winning strategies. We use the game to prove and reprove some new and older inscribing theorems for sigma-ideals of …