CHARACTERIZATIONS OF THE SERIES GROUP GENERATORS ON HILBERT SPACES AND THE -CALCULUS
We give necessary and sufficient conditions for the sequence of operators on a Hilbert space to have a bounded -calculus on a vertical strip symmetric to the imaginary axis. From this, a characterization of group generators on Hilbert spaces is obtained yielding recent results of Liu and Zwart as corollaries by Haase [9].
-group, -calculus.