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

March 11, 2015, 4:15 p.m.
Wiesław Kubiś (Jan Kochanowski University in Kielce and Mathematical Institute of the Czech Academy of Sciences)
On perfect monochromatic sets in analytic spaces
It is known that if C is a G-delta symmetric relation in an analytic space and there exists an uncountable C-monochromatic set then there exists also a perfect one. We extend this result to the …
March 4, 2015, 4:15 p.m.
Witold Marciszewski (Uniwersytet Warszawski)
Combinatorial methods in investigations of extension operators
Jan. 21, 2015, 4:15 p.m.
Jacek Tryba (doktorant UG)
BW property for van der Waerden and Hindman ideals
We consider four classes of topological spaces defined with the aid of convergence with respect to ideals on the set of natural numbers and examine the relationships between each other. We also show that two …
Jan. 14, 2015, 4:15 p.m.
Piotr Zakrzewski (Uniwersytet Warszawski)
Combinatorics of ideals -- selectivity versus density; the second part.
An ideal I on $\omega$ is called: - dense if every infinite subset of $\omega$ contains an infinite subset in I, - selective if for every partition (A_n) of $\omega$ such that no finite union …
Dec. 10, 2014, 4:15 p.m.
Piotr Zakrzewski (Uniwersytet Warszawski)
Combinatorics of ideals -- selectivity versus density
An ideal I on $\omega$ is called: - dense if every infinite subset of $\omega$ contains an infinite subset in I, - selective if for every partition (A_n) of $\omega$ such that no finite union …
Dec. 3, 2014, 4:15 p.m.
Piotr Koszmider (IMPAN)
Automorphisms of the Banach space C(N*)
The classical topic of automorphisms of the Boolean algebra P(N)/Fin is one of the most exciting chapters of the set-theoretic research. One of its achievements is the result saying that assuming PFA or OCA+MA any …
Nov. 26, 2014, 4:15 p.m.
Grzegorz Plebanek (Uniwersytet Wrocławski)
On some compactifications of N
We consider (zerodimensional) compactifications of the set of natural numbers such that the remainder is not separable but supports a probability measure. It seems to be unclear if such a compactification can be constructed within …
Nov. 19, 2014, 4:15 p.m.
Michał Korch (doktorant UW)
joint work with T. Weiss (The class of perfectly null sets and its transitive version)
The ideals of universally null sets (UN, sets which are null with respect to any Borel diffused measure) and perfectly meager sets (PM, sets which are meager when restricted to any perfect set) are best …
Nov. 5, 2014, 4:15 p.m.
Marcin Szyszkowski (Uniwersytet Gdański)
On axial functions
A function f : X × Y → X × Y is axial if it is of one of two types:f(x, y) = (g(x, y), y) for some g : X × Y → X …
Oct. 29, 2014, 4:15 p.m.
Rafał Filipów (Uniwersytet Gdański)
Yet another ideal version of the bounding number b
We give a sufficient and necessary condition when the ideal pointwise convergence implies the ideal equal (aka quasi-normal) convergence. The characterization is expressed in terms of a cardinal coefficient related to the bounding number $\mathfrak{b}$. …
Oct. 22, 2014, 4:15 p.m.
Taras Banakh (Lviv National University and UJK Kielce)
A characterization of Tychonoff spaces with applications to paratopological groups
We prove that a regular topological space $X$ is Tychonoff if and only if its topology is generated by a quasi-uniformity $\U$ such that for every $U\in\U$ and $A\subset X$ there is $V\in\U$ such that …
Oct. 15, 2014, 4:15 p.m.
Maciej Malicki (SGH)
Abelian pro-countable groups and orbit equivalence relations -part II
Oct. 8, 2014, 4:15 p.m.
Maciej Malicki (SGH)
Abelian pro-countable groups and orbit equivalence relations
June 4, 2014, 4:15 p.m.
Marcin Staniszewski (Doktorant UG)
quasi-normal) convergence via ideal (Pointwise versus equal)
May 28, 2014, 4:15 p.m.
Wiesław Kubiś (Jan Kochanowski University in Kielce and Mathematical Institute of the Czech Academy of Sciences)
Katetov functors; joint work with Dragan Masulovic (Novi Sad)
We shall describe a natural method for constructing Fraisse limits by iterating a special functor F such that F(X) realizes all possible ``simple" extensions of the model X in a fixed class, usually consisting of …