We show that if B is a C*-subalgebra of a C*-algebra A such that B contains a bounded approximate identity for A,and if L is the pull-back to A of the quotient norm on A/B,then L is strongly Leibniz.In connection with...We show that if B is a C*-subalgebra of a C*-algebra A such that B contains a bounded approximate identity for A,and if L is the pull-back to A of the quotient norm on A/B,then L is strongly Leibniz.In connection with this situation we study certain aspects of best approximation of elements of a unital C*-algebra by elements of a unital C*-subalgebra.展开更多
1 Introduction and main resultsARVESON in ref. [1] generalized the classical Hahn-Banach Extension Theorem for linear func-tionals to the self-adjoint linear closed subspace of C~* -algebras. From then on numerous au-...1 Introduction and main resultsARVESON in ref. [1] generalized the classical Hahn-Banach Extension Theorem for linear func-tionals to the self-adjoint linear closed subspace of C~* -algebras. From then on numerous au-thors have given various generalizations of the non-commutative Hahn-Banach-Arveson Theo-rem of ref. [1]. The following extension theorem is due to G. Wittstock.展开更多
基金supported in part by US National Science Foundation (Grant No. DMS-0753228)
文摘We show that if B is a C*-subalgebra of a C*-algebra A such that B contains a bounded approximate identity for A,and if L is the pull-back to A of the quotient norm on A/B,then L is strongly Leibniz.In connection with this situation we study certain aspects of best approximation of elements of a unital C*-algebra by elements of a unital C*-subalgebra.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 19671042).
文摘1 Introduction and main resultsARVESON in ref. [1] generalized the classical Hahn-Banach Extension Theorem for linear func-tionals to the self-adjoint linear closed subspace of C~* -algebras. From then on numerous au-thors have given various generalizations of the non-commutative Hahn-Banach-Arveson Theo-rem of ref. [1]. The following extension theorem is due to G. Wittstock.
