Published online by Cambridge University Press: 20 November 2018
Throughout this paper will denote a C*-algebra and
will denote its second dual, which is identified with the enveloping von Neumann algebra of
. A projection E in
is said to be open if it supports a left ideal in
, that is, if
E =
- for some left ideal
in
. Here the bar - means the stong closure. When
has a unit, this definition coincides with the definition of Akemann [1, Definition II. 1]. In the sequel, we shall solely be concerned with two-sided ideals, and consequently central projections [4, I, § 3, Corollary 3 of Theorem 2]. Our aim is to show that
is CCR if and only if the open central projections are strongly dense in the set of central projections on
.