Pseudospectra of semigroup generators
Eugene Shargorodsky · Bulletin of the London Mathematical Society · 2010
It is proved that the resolvent norm of the infinitesimal generator of a C0 semigroup on a complex uniformly convex Banach space cannot be constant on a nonempty open set. In the case of Hilbert spaces, this result answers a question posed by J. R. Partington.