From kubis at math.cas.cz Fri Nov 19 23:00:01 2021 From: kubis at math.cas.cz (kubis at math.cas.cz) Date: Fri, 19 Nov 2021 23:00:01 +0100 MIME-Version: 1.0 Subject: [Settfa] Tuesday 23/11, Pawel Gladki Message-ID: <20211119220001.D0BE520F9@web.math.cas.cz> ------------------------------------------------------------------------- Tuesday 23rd November, 10:00am Place: IM in kon?rna  ------------------------------------------------------------------------- Speaker:Pawel Gladki, University of Silesia in Katowice, Poland Title: On the categories of superpowersets and superpowergroups Abstract In this talk we shall introduce the notion of superpowersets and superpowergroups, which are objects that provide a new approach to studying powersets of groups, as well as hypergroups (that is group-like objects with multivalued binary operation) and some fuzzy algebras. As an application, we shall show how the classical quadratic form theory over fields can be axiomatized using these tools, and how some rather difficult to phrase questions such as the question of Witt equivalence of fields, can be easily stated in the language of superpowergroups. For more information see the seminar web page at https://calendar.math.cas.cz/set-theory-and-analysis-actual . From kubis at math.cas.cz Fri Nov 26 21:00:02 2021 From: kubis at math.cas.cz (kubis at math.cas.cz) Date: Fri, 26 Nov 2021 21:00:02 +0100 MIME-Version: 1.0 Subject: [Settfa] Tuesday 30/11, N. Christopher Phillips Message-ID: <20211126200002.A6AC22C17@web.math.cas.cz> ------------------------------------------------------------------------- Tuesday 30th November, 10:00am Place: IM in kon?rna  ------------------------------------------------------------------------- Speaker:N. Christopher Phillips, University of Oregon Title: Incompressible Banach algebras Abstract Let A be a Banach algebra. We say that A is incompressibleif every injective homomorphism from A to another Banach algebrais bounded below, uniformly incompressible if there is a nonzerolower bound depending only on the norm of the homomorphism, andisometrically incompressible if every contractive injectivehomomorphism from A to another Banach algebra is isometric.Incompressibility has been considered (under other names) in thepast, although without any systematic theory. For example, thealgebra of bounded operators on a Banach space, certain Calkinalgebras, and all C*-algebras are uniformly and isometricallyincompressible. The last result has led to the idea that a "C* like"L^p operator algebra should be incompressible. The disk algebra andthe algebra of bounded infinite upper triangular matrices are notincompressible. We describe some of the basic theory of incompressible Banachalgebras and some of the examples. This talk will use very littlemachinery. This is joint work with Bill Johnson and Gideon Schechtman. For more information see the seminar web page at https://calendar.math.cas.cz/set-theory-and-analysis-actual .