hypercyclic. This is a useful tool to prove that an operator is convex-cyclic and it provides a
large number of examples of convex-cyclic operators. A complex number λ λ is said to be an
extended eigenvalue of a bounded linear operator T if there exists a non-zero bounded
linear operator X such that TX= λ XT TX= λ XT. We will discover some necessary conditions
on the extended spectrum of an operator to be a convex-cyclic operator. These conditions …