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 constanthttp://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 schedulehttp://www.math.unt.edu/~bunyamin/banach May 1 Daniel Freemanhttp://www.math.unt.edu/~bunyamin/banach#Daniel%20Freeman St Louis University May 8 Chris Gartlandhttp://www.math.unt.edu/~bunyamin/banach#Chris%20Gartland UIUC May 15 Gideon Schechtmanhttp://www.math.unt.edu/~bunyamin/banach#Gideon%20Schechtman Weizmann Institute of Science May 22 Pedro Tradacetehttp://www.math.unt.edu/~bunyamin/banach#Pedro%20Tradacete Instituto de Ciencias Matemáticas May 29 Miguel Martinhttp://www.math.unt.edu/~bunyamin/banach#Miguel%20Martin University of Granada June 5 Denny Leunghttp://www.math.unt.edu/~bunyamin/banach#Denny%20Leung National University of Singapore June 12 Noé de Rancourthttp://www.math.unt.edu/~bunyamin/banach#No%C3%A9%20de%20Rancourt Kurt Gödel Research Center June 19 Christian Rosendalhttp://www.math.unt.edu/~bunyamin/banach#Christian%20Rosendal UIC and NSF June 26 Pete Casazzahttp://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 Seminarshttps://mathseminars.org/.

Thank you, and best regards,

Bunyamin Sari