| Citation | Ringrose has made major contributions to the theory of algebras of operators on Hilbert spaces. In collaboration with R.V. Kadison he has developed the fundamental properties of derivations and automorphisms on C*-algebras. Their result that all derivations on certain von Neumann algebras are inner was later extended to all C*-algebras by S. Sakai. Also particularly noteworthy is their theorem that every star automorphism on a C*-algebra within distance 2 from the identity belongs to a norm continuous one parameter group of automorphisms, and is therefore implemented by a unitary operator on the underlying Hilbert space. Ringrose has also done important work in other branches of functional analysis, notably in the detailed study of operators of the Schmidt class. |