© 1994 by London Mathematical Society
© The London Mathematical Society
Inner Derivations and Primal Ideals of C*-Algebras
Department of Mathematics and Statistics, University of Newcastle-upon-Tyne Newcastle-upon-Tyne NE1 7RU
Received 27 October 1992.
Let A be a C*-algebra. For a
A let D(a, A) denote the inner derivation induced by a, regarded as a bounded operator on A, and let d(a, Z(A)) denote the distance of a from Z(A), the centre of A. Let K(A) be the smallest number in [0,
] such that d(a, Z(A))
K(A)||D(a, A)|| for all a
A. It is shown that if A is non-commutative and has an identity then either K(A) =
, or K(A) = 1 /
3, or K(A)
1. Necessary and sufficient conditions for these three possibilities are given in terms of the primitive and primal ideals of A. If A is a quotient of an AW*-algebra then K(A)
. Helly's Theorem is used to show that if A is a weakly central C*-algebra then K(A)
1.