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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

  • 2024-02-28, godz. 16:15, 5050

    Robert Simon (London School of Economics)

    Paradoxical colouring rules

    A colouring rule is a way to determine a function from a probability space to a set of colours based on the colours of finitely many measure preserving transformations. It is paradoxical if there is some function that satisfies the rule however there is no way to satisfy the rule that is measurable...

  • 2024-01-24, godz. 16:15, Zoom

    Taras Banakh (Ivan Franko National University of Lviv and UJK Kielce)

    Strongly rigid countable Hausdorff spaces

    A topological space $X$ is strongly rigid if every no-identity continuous self-map of $X$ is constant. Among known examples of strongly rigid spaces one can recall the famous Cook continua. In fact, every strongly rigid topological space is connected. We shall explain how to construct strongly rig...

    slides

  • 2024-01-10, godz. 16:15, 5050

    Piotr Szewczak (Cardinal Stefan Wyszyński University in Warsaw)

    Concentrated sets in the Miller model

    A set of reals X is concentrated if it is uncountable and there is a countable subset D of X such that for each open set U containing D the set X\U is countable. Using combinatorial covering properties, we show that there is no concentrated set of reals of size omega_2 in the Miller model. This resu...

    Materiały dotyczące referatu

  • 2023-12-20, godz. 16:15, 5050

    Zdeněk Silber (IM PAN)

    A countably tight P(K) space admitting a nonseparable measure

    In the talk we focus on the relation of countable tightness of the space P(K) of Radon probabilty measures on a compact Hausdorff space K and of existence of measures in P(K) that have uncountable Maharam type. Recall that a topological space X has countable tightness if any element of the closure o...

  • 2023-12-13, godz. 16:15, 5050

    Maciej Malicki (IM PAN)

    Compacta and their homeomorphism groups from posets, part 2

    Very recently A. Bartoš, T. Bice and A. Vignati discovered a duality, generalizing the Stone duality, between second countable T_1 compacta and graded omega-posets. Their approach allows for elementary combinatorial constructions, in the spirit of Fraïssé theory, of classical cont...

  • 2023-12-06, godz. 16:15, 5050

    Adam Bartoš ("An introduction to abstract Fraïssé theory") and Wiesław Kubiś ("Uncountable homogeneous structures") (Institute of Mathematics of the Czech Academy of Sciences)

    "An introduction to abstract Fraïssé theory" and "Uncountable homogeneous structures"

    "An introduction to abstract Fraïssé theory": We give a gentle introduction to abstract countable discrete Fraïssé theory. First, we recall three classical examples of ultrahomogeneous structures: the linear order of the rationals, the random graph, and the Urysohn...

    Materiały dotyczące referatu

    Materiały dotyczące referatu

  • 2023-11-29, godz. 16:15, 5050

    Maciej Malicki (IM PAN)

    Compacta and their homeomorphism groups from posets

    Very recently A. Bartoš, T. Bice and A. Vignati discovered a duality, generalizing the Stone duality, between second countable T_1 compacta and graded omega-posets. Their approach allows for elementary combinatorial constructions, in the spirit of Fraïssé theory, of classical cont...

  • 2023-11-22, godz. 16:15, 5050

    Jindrich Zapletal (University of Florida)

    Fraenkel-Mostowski models revisited

    A dynamical ideal is a group G acting on a set X, together with an ideal I on X invariant under the action. A dynamical ideal comes with an associated model of ZF set theory. I will discuss several theorems which connect dynamical properties of the ideal with fragments of axiom of choice in the asso...

    Materiały dotyczące referatu

  • 2023-11-08, godz. 16:15, 5050

    David Chodounsky (Institute of Mathematics of the Czech Academy of Sciences)

    Games for chromatic numbers of analytic graphs

    We define games which characterize countable coloring numbers of analytic graphs on Polish spaces. These games can provide simple verification of the countable chromatic number of certain graphs. We also get a simpler proof of a dichotomy originally proved by Adams and Zapletal: if an analytic graph...

    Materiały dotyczące referatu

  • 2023-10-25, godz. 16:15, 5050

    Tomasz Kochanek (University of Warsaw)

    Operator semigroups in the Calkin algebra, part 2

    The abstract of the talk can be found here: https://drive.google.com/file/d/1xCTvKwjFXONxqUN1NurltvhGewn6GyV7/view?usp=sharing ...

    abstract, part 2

Strony