2 papers
math.FA2026
Invariant subspaces for operators with spectrum containing the boundary of the numerical range
Vladimir Müller, Yuri Tomilov
We prove that a bounded Hilbert space operator has a nontrivial invariant subspace whenever its spectrum contains the topological boundary of its numerical range. We also give vari…
math.FA2025
Real linear operators and numerical ranges
Damian KoÅaczek, Vladimir Müller
Real linear operators between two complex Banach spaces unify naturally two important classes of linear operators and antilinear operators. We give a survey of basic geometric, spe…