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Wydział Matematyki, Informatyki i Mechaniki Uniwersytetu Warszawskiego

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Seminarium „Topologia i teoria mnogości”

Cotygodniowe seminarium badawcze


Lista referatów

  • 2018-05-23, godz. 16:15, 5050

    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 wzgl...

  • 2018-05-16, godz. 16:15, 5050

    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 the following result (joint with T. Ibarlucia): the full group of any minimal homeomorphism is a coana...

  • 2018-05-09, godz. 16:15, 5050

    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 are ordinary divergent sequences that are convergent in these new me...

  • 2018-04-25, godz. 16:15, 5050

    Andrzej Szymański (Cardinal Stefan Wyszyński University in Warsaw)

    KKM Theorem: From L*-operators to a Renting Problem

    The abstract of the talk

  • 2018-04-11, godz. 16:15, 5050

    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 in the celebrated Pontrjagin duality theorem for LCA groups). All direct products Z^kappa of the addit...

  • 2018-03-21, godz. 16:15, 5050

    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, consequence of the Continuum Hypothesis. We also establish t...

  • 2018-03-14, godz. 16:15, 5050

    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. In 1975, D. Pincus and K. Prikry asked "whether a Hamel basis exists in any model in which R cannot be well ordered.&q...

  • 2018-03-07, godz. 16:15, 5050

    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 Eberlein compact space contain a closed zero-dimensional, nonmetrizable subspace? We will cons...

  • 2018-02-28, godz. 16:15, 5050

    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 ∈ J) if C ∩ f is non-empty for every closed C ⊂ R^2 with dom(C) of size c. M. Fenoy-Munoz, J.L. Gamez-Merino, G.A. Munoz-Fernandez a...

  • 2018-01-24, godz. 16:15, 5050

    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 $X$ to be null-finite if there exists an infinite compact subset $K\subset X$ such that for every $...

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