Please use this identifier to cite or link to this item: http://hdl.handle.net/10525/2619

 Title: Convexity around the Unit of a Banach Algebra Authors: Kadets, VladimirKatkova, OlgaMartín, MiguelVishnyakova, Anna Keywords: Unital Banach AlgebraStrongly Extreme PointMidpoint Modulus of Local Convexity Issue Date: 2008 Publisher: Institute of Mathematics and Informatics Bulgarian Academy of Sciences Citation: Serdica Mathematical Journal, Vol. 34, No 3, (2008), 619p-628p Abstract: We estimate the (midpoint) modulus of convexity at the unit 1 of a Banach algebra A showing that inf {max±||1 ± x|| − 1 : x ∈ A, ||x||=ε} ≥ (π/4e)ε²+o(ε²) as ε → 0. We also give a characterization of two-dimensional subspaces of Banach algebras containing the identity in terms of polynomial inequalities. Description: 2000 Mathematics Subject Classification: Primary: 46B20. Secondary: 46H99, 47A12. URI: http://hdl.handle.net/10525/2619 ISSN: 1310-6600 Appears in Collections: Volume 34, Number 3

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