4 papers
Pseudospectrum enclosures by discretization
Andreas Frommer, Birgit Jacob, Lukas Vorberg +2
A new method to enclose the pseudospectrum via the numerical range of the inverse of a matrix or linear operator is presented. The method is applied to finite-dimensional discretiz…
Krylov type methods exploiting the quadratic numerical range
Andreas Frommer, Birgit Jacob, Karsten Kahl +2
The quadratic numerical range is a subset of the standard numerical range of a linear operator which still contains its spectrum. It arises naturally in operators which ha…
Stability radius for infinite-dimensional interconnected systems
Birgit Jacob, Sebastian Möller, Christian Wyss
The stability radius for finitely many interconnected linear exponentially stable well-posed systems with respect to static perturbations is studied. If the output space of each sy…
Dichotomous Hamiltonians and Riccati equations for systems with unbounded control and observation operators
Christian Wyss
The control algebraic Riccati equation is studied for a class of systems with unbounded control and observation operators. Using a dichotomy property of the associated Hamiltonian…