On semi-groups in Banach algebras close to the identity
On semi-groups in Banach algebras close to the identity
In their recent paper [1], Nakamura and Yoshida showed that the identity I is the only bounded operator T on a Hilbert space which satisfies II Tn-Ill _ 1 for n-1, 2, 3, Their proof is based on the mean ergodic theorem.