Dear all, The next Banach spaces webinar is on Friday April 24 9AM CDT (e.g., Dallas, TX time). Please join us at https://unt.zoom.us/j/512907580 Speaker: Tomasz Kania, Czech Academy Title: Quantifying Kottman's constant<http://www.math.unt.edu/~bunyamin/banach#Tomasz%20Kania> Abstract. Kottman's constant, K(X), of a Banach space X is the supremum over those d>0 for which the unit sphere of X contains a d-separated sequence. It is known that K(X)>1 for every infinite-dimensional space X (the Elton–Odell theorem). I will present certain estimates related to interpolation spaces, twisted sums, and other classes of Banach spaces X concerning the isomorphic Kottman constant, defined as the infimum of K(Y), where Y ranges over all renormings of X. I will also comment on other related constants (such as the disjoint one defined for Banach lattices) and their symmetric analogs. This talk is based on papers with J. M. F. Castillo, M, González, P. L. Papini (PAMS 2020+)<https://arxiv.org/abs/1910.01626> and P. Hájek, T. Russo (JFA 2018)<https://arxiv.org/abs/1803.11501>. Upcoming schedule<http://www.math.unt.edu/~bunyamin/banach> May 1 Daniel Freeman<http://www.math.unt.edu/~bunyamin/banach#Daniel%20Freeman> St Louis University May 8 Chris Gartland<http://www.math.unt.edu/~bunyamin/banach#Chris%20Gartland> UIUC May 15 Gideon Schechtman<http://www.math.unt.edu/~bunyamin/banach#Gideon%20Schechtman> Weizmann Institute of Science May 22 Pedro Tradacete<http://www.math.unt.edu/~bunyamin/banach#Pedro%20Tradacete> Instituto de Ciencias Matemáticas May 29 Miguel Martin<http://www.math.unt.edu/~bunyamin/banach#Miguel%20Martin> University of Granada June 5 Denny Leung<http://www.math.unt.edu/~bunyamin/banach#Denny%20Leung> National University of Singapore June 12 Noé de Rancourt<http://www.math.unt.edu/~bunyamin/banach#No%C3%A9%20de%20Rancourt> Kurt Gödel Research Center June 19 Christian Rosendal<http://www.math.unt.edu/~bunyamin/banach#Christian%20Rosendal> UIC and NSF June 26 Pete Casazza<http://www.math.unt.edu/~bunyamin/banach#Pete%20Casazza> University of Missouri The video of last week’s talk is available here <https://youtu.be/ynSsWJwCeQA> * For more information please visit the webinar website http://www.math.unt.edu/~bunyamin/banach * For a comprehensive list of talks in all areas of maths see the website Math Seminars<https://mathseminars.org/>. Thank you, and best regards, Bunyamin Sari