ABSTRACT
Let be an arbitrary unital *-algebra over the real or complex field , and let with . Assume that is a map. It is shown that, if satisfies for each and projection then and for all . Also, if is a nest algebra on Hilbert space and is a surjective map that satisfies for each and all idempotents P in , then we characterize the concrete form of on .
Notes
No potential conflict of interest was reported by the authors.