© 1999 by London Mathematical Society
Ideal Spaces of Banach Algebras
Department of Mathematical Sciences, University of Aberdeen Aberdeen, AB24 3UE, U.K. E-mail: ds{at}maths.abdn.ac.uk
Received 21 March 1997. Revision received 13 November 1997.
The ideal space Id(A) of a Banach algebra A is studied as a bitopological space Id(A),
u,
n, where
u is the weakest topology for which all the norm functions I
|| a + I|| (with a
A and I
Id(A)) are upper semi-continuous, and
n is the de Groot dual of
u. When A is separable,
n
u is either a compact, metrizable topology, or it is neither Hausdorff nor first countable. TAF-algebras are shown to exhibit the first type of behaviour. Applications to Banach bundles (which motivate the study), and to PI-Banach algebras, are given. 1991 Mathematics Subject Classification: 46H10, 46J20.