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Cotygodniowe seminarium badawcze
Organizatorzy
- prof. dr hab. Witold Marciszewski
- prof. dr hab. Piotr Zakrzewski
Informacje
środy, 16:15 , sala: 5050Dziedziny badań
Lista referatów
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26 kwietnia 2023 16:15
Jarosław Swaczyna (Lodz University of Technology)
Continuity of coordinate functionals for ideal Schauder basis
Given an ideal of subsets of natural numbers I we say that a sequence (x_n) is I-convergent to x if for every ε>0 condition {n \in N:d(x_n,x)>ε}\in I holds. We may use this notion to …
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19 kwietnia 2023 16:15
Tomasz Weiss (Cardinal Stefan Wyszyński University in Warsaw)
Countably perfectly meager and countably perfectly null sets
We study a strengthening of the notion of a universally meager set and its dual counterpart that strengthens the notion of a universally null set. We say that a subset A of a perfect Polish …
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29 marca 2023 16:15
Daria Michalik (University of Warsaw)
Blocking properties of the diagonal in Cartesian product
The abstract of the talk can be found on the webpage of our seminar: https://www.mimuw.edu.pl/en/seminaria/topology-and-set-theory-seminar
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22 marca 2023 16:15
Taras Banakh (Ivan Franko National University of Lviv and UJK Kielce)
An example of a 36-Shelah group
A group $G$ is called $n$-Shelah if $G=A^n$ for any subset $A\subseteq G$ of cardinality $|A|=|G|$. In 1980 Saharon Shelah constructed his famous CH-example of an uncountable 6640-Shelah group. This group was the first example …
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15 marca 2023 16:15
Wiesław Kubiś (Akademia Nauk Republiki Czeskiej)
Ultrametric homogeneous structures
We shall present the theory of homogeneous Polish ultrametric structures. Our starting point is a Fraı̈ssé class of finite structures and the crucial tool is the universal homogeneous epimorphism. The new Fraı̈ssé limit is an …
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8 marca 2023 16:15
Zdeněk Silber (IM PAN)
Weak* derived sets
The weak* derived set of a subset A of a dual Banach space X* is the set of weak* limits of bounded nets in A. It is known that a convex subset of a dual …
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1 marca 2023 16:15
Adam Kwela (University of Gdańsk)
Katětov order and its applications
This talk is an overview of my recent articles on ideals on countable sets. I will present set-theoretic and topological applications of Katětov order on ideals, focusing on distinguishing certain classes of sequentially compact spaces …
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25 stycznia 2023 16:15
Kamil Ryduchowski (Doctoral School of Exact and Natural Sciences UW)
On antiramsey colorings of uncountable squares and geometry of nonseparable Banach spaces
A subset Z of a Banach space X is said to be r-equilateral (r-separated) if every two distinct elements of Z are in the distance exactly (at least) r from each other. We will address …
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18 stycznia 2023 16:15
Piotr Szewczak (Cardinal Stefan Wyszyński University in Warsaw)
Totally imperfect Menger sets: Part 2
A set of reals X is Menger if for any countable sequence of open covers of X one can pick finitely many elements from every cover in the sequence such that the chosen sets cover …
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11 stycznia 2023 16:15
Piotr Szewczak (Cardinal Stefan Wyszyński University in Warsaw)
Totally imperfect Menger sets
A set of reals X is Menger if for any countable sequence of open covers of X one can pick finitely many elements from every cover in the sequence such that the chosen sets cover …
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21 grudnia 2022 16:15
Damian Sobota (Universität Wien, Kurt Gödel Research Center for Mathematical Logic)
On continuous operators from Banach spaces of Lipschitz functions onto c_0
During my talk I will discuss some of our recent results concerning the existence of continuous operators from the Banach spaces Lip_0(M) of Lipschitz real-valued functions on metric spaces M onto the Banach space c_0 …
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14 grudnia 2022 16:15
Piotr Koszmider (IM PAN)
Overcomplete sets
The density of a topological vector space (tvs) X is the minimal cardinality of a dense subset of X. A subset of a tvs is called linearly dense if the set of all linear combinations …
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7 grudnia 2022 16:15
Tomasz Kania (Jagiellonian University)
Renormings of c_0(Γ)
A biorthogonal system in a Banach space is called Auerbach whenever both the vectors and the associated functionals are precisely of norm 1. We will show that assuming the Continuum Hypothesis, there exist renormings of …
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30 listopada 2022 16:15
Witold Marciszewski (University of Warsaw)
On \omega-Corson compact spaces and related classes of Eberlein compacta
Recall that a compact space K is Eberlein compact if it can be embedded into some Banach space X equipped with the weak topology. A compact space K is \omega-Corson compact if, for some set …
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16 listopada 2022 16:15
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 …
