Maps Preserving the Numerical Radius Distance Between C*-Algebras

摘要

Let A and B be unital C *-algebras, and let v(a) be the numerical radius of any element a. A. We show that if a map T from A ontoB satisfies v(T (a)-T (b)) = v(a -b), (a, b. A), then T (1) -T (0) is a unitary central element in B. This shows that the characterization of Bai, Hou and Xu for the numerical radius distance preservers onC *-algebras can be obtained without the extra condition that T (1)-T (0) is in the center of B.