April 2022
Aleksander Cieślak: Marczewski ideals of product trees
24/04/22 15:37
Tuesday, April 26, 2022 17:00
Location: room 605, Mathematical Institute, University of Wroclaw
Speaker: Aleksander Cieślak
Title: Marczewski ideals of product trees
Abstract: We investigate Marczewski style ideals associated with the product of two tree-like forcing notions and compare these to original, one dimensional ones.
Location: room 605, Mathematical Institute, University of Wroclaw
Speaker: Aleksander Cieślak
Title: Marczewski ideals of product trees
Abstract: We investigate Marczewski style ideals associated with the product of two tree-like forcing notions and compare these to original, one dimensional ones.
Konrad Królicki: Nonsingular hyperfinite actions of groups
09/04/22 15:36
Tuesday, April 12, 2022 17:00
Location: room 605, Mathematical Institute, University of Wroclaw
Speaker: Konrad Królicki (Hungarian Academy of Sciences)
Title: Nonsingular hyperfinite actions of groups
Abstract: Any action of a finitely generated group on a standard probability space induces a measurable Schreier graph.When the action is nonsingular, i.e. it preserves the measure class, the measurable graph is called a measured graphing. We say that a measured graphing is hyperfinite if for any \(\varepsilon >0\), one can remove a part of measure at most \(\varepsilon\) in such a way that the components of the remainder are finite. I will define the notion of local convergence for measured graphs, i.e. finite Schreier graphs with a probability measure on their vertices, and how their limits may be represented with nonsingular actions. The objective of the talk is to present one part of the nonsingular theorem of Schramm: if a sequence of measured graphs is hyperfinite, then the limit graphing is hyperfinite as well. Joint work with Gabor Elek.
Location: room 605, Mathematical Institute, University of Wroclaw
Speaker: Konrad Królicki (Hungarian Academy of Sciences)
Title: Nonsingular hyperfinite actions of groups
Abstract: Any action of a finitely generated group on a standard probability space induces a measurable Schreier graph.When the action is nonsingular, i.e. it preserves the measure class, the measurable graph is called a measured graphing. We say that a measured graphing is hyperfinite if for any \(\varepsilon >0\), one can remove a part of measure at most \(\varepsilon\) in such a way that the components of the remainder are finite. I will define the notion of local convergence for measured graphs, i.e. finite Schreier graphs with a probability measure on their vertices, and how their limits may be represented with nonsingular actions. The objective of the talk is to present one part of the nonsingular theorem of Schramm: if a sequence of measured graphs is hyperfinite, then the limit graphing is hyperfinite as well. Joint work with Gabor Elek.
Adam Bartos: Hereditarily indecomposable continua as Fraïssé limits
02/04/22 17:44
Tuesday, April 5, 2022 17:00
Location: room 605, Mathematical Institute, University of Wroclaw
Speaker: Adam Bartos (Czech Academy of Sciences)
Title: Hereditarily indecomposable continua as Fraïssé limits
Abstract: Irwin and Solecki introduced projective Fraïssé theory and showed that the Fraïssé limit of the projective class of finite linear graphs is a pre-space of the pseudo-arc. This allowed to characterize the pseudo-arc as the unique approximatively projectively homogeneous arc-like continuum. We introduce a framework for Fraïssé theory where the pseudo-arc itself is a Fraïssé limit, and apply the framework to obtain similar characterizations for P-adic pseudo-solenoids. This is joint work with Wiesław Kubiś.
Location: room 605, Mathematical Institute, University of Wroclaw
Speaker: Adam Bartos (Czech Academy of Sciences)
Title: Hereditarily indecomposable continua as Fraïssé limits
Abstract: Irwin and Solecki introduced projective Fraïssé theory and showed that the Fraïssé limit of the projective class of finite linear graphs is a pre-space of the pseudo-arc. This allowed to characterize the pseudo-arc as the unique approximatively projectively homogeneous arc-like continuum. We introduce a framework for Fraïssé theory where the pseudo-arc itself is a Fraïssé limit, and apply the framework to obtain similar characterizations for P-adic pseudo-solenoids. This is joint work with Wiesław Kubiś.