Some Perturbation Results for Analytic Semigroups.
A note on the comparison of C0-semigroups.
On relatively bounded perturbations of linear -semigroups
Hypercyclicity of Semigroups is a Very Unstable Property
Hypercyclicity of -semigroups is a very unstable property: We give examples to show that adding arbitrary small constants or a bounded rank one operator to the generator of a hypercyclic semigroup can destroy hypercyclicity. Also the limit of hypercyclic semigroups (even in operator norm topology) need not be hypercyclic, and a hypercyclic semigroup can be the limit of nonhypercyclic ones. Hypercyclicity is not inherited by the Yosida approximations. Finally, the restriction of...
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