Ziemowit Kostana
Ziemowit Kostana: Cohen-like poset for adding Fraisse limits
30/04/20 14:59
Tuesday, May 5, 2020 17:15
Location: Zoom.us: if you want to participate please contact organizers
Speaker: Ziemowit Kostana (University of Warsaw)
Title: Cohen-like poset for adding Fraisse limits
Abstract. There exist a natural forcing notion which turns given countable set into a Fraisse limit of a given Fraisse class. This long-known phenomenon provided a rough intuition that Fraisse limits, as "generic structures", have some connections with forcing. The goal of the talk is to look at some particular instances and possible applications of this idea.
Location: Zoom.us: if you want to participate please contact organizers
Speaker: Ziemowit Kostana (University of Warsaw)
Title: Cohen-like poset for adding Fraisse limits
Abstract. There exist a natural forcing notion which turns given countable set into a Fraisse limit of a given Fraisse class. This long-known phenomenon provided a rough intuition that Fraisse limits, as "generic structures", have some connections with forcing. The goal of the talk is to look at some particular instances and possible applications of this idea.
Ziemowit Kostana: Non-measurabity of algebraic sum
11/10/17 23:05
Tuesday, October 17, 2017 17:15
Room: D1-215
Speaker: Ziemowit Kostana
Title: Non-measurabity of algebraic sum
Abstract. Consider following problems:
It is not hard to prove that positive answer to 2. implies positive answer to 1, both for measure and category. We answer 2. affirmatively for category, while version for measure turns out to be independent of ZFC. The latter was essentially proved last year by A. Rosłanowski and S. Shelah. Both results holds for Cantor space with coordinatewise addition mod. 2 as well.
Room: D1-215
Speaker: Ziemowit Kostana
Title: Non-measurabity of algebraic sum
Abstract. Consider following problems:
- If \(A\) is meagre (null) subset of real line, does there necessarily exist set \(B\) such that algebraic sum \(A+B\) doesn't have Baire property (is non-measurable)?
- If \(A\) is meagre (null) subset of real line, does there necessarily exist non-meagre (non-null) additive subgroup, disjoint with some translation of \(A\)?
It is not hard to prove that positive answer to 2. implies positive answer to 1, both for measure and category. We answer 2. affirmatively for category, while version for measure turns out to be independent of ZFC. The latter was essentially proved last year by A. Rosłanowski and S. Shelah. Both results holds for Cantor space with coordinatewise addition mod. 2 as well.