33 citations · 72 across the 8 of their papers we have counts for
10 papers
Computing the Quadratic Numerical Range
Birgit Jacob, Lukas Vorberg, Christian Wyss
A novel algorithm for the computation of the quadratic numerical range is presented and exemplified yielding much better results in less time compared to the random vector sampling…
Stability via closure relations with applications to dissipative and port-Hamiltonian systems
Jochen Glück, Birgit Jacob, Annika Meyer +2
We consider differential operators that can be represented by means of a so-called closure relation in terms of a simpler operator defined on a larger…
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…
On the Spectral Decomposition of Dichotomous and Bisectorial Operators
Monika Winklmeier, Christian Wyss
For an unbounded operator on a Banach space the existence of invariant subspaces corresponding to its spectrum in the left and right half-plane is proved. The general assumptio…
Dichotomous Hamiltonians with Unbounded Entries and Solutions of Riccati Equations
Christiane Tretter, Christian Wyss
An operator Riccati equation from systems theory is considered in the case that all entries of the associated Hamiltonian are unbounded. Using a certain dichotomy property of the H…
Hamiltonians with Riesz Bases of Generalised Eigenvectors and Riccati Equations
Christian Wyss
An algebraic Riccati equation for linear operators is studied, which arises in systems theory. For the case that all involved operators are unbounded, the existence of infinitely m…
Riesz Bases for p-Subordinate Perturbations of Normal Operators
Christian Wyss
For p-subordinate perturbations of unbounded normal operators, the change of the spectrum is studied and spectral criteria for the existence of a Riesz basis with parentheses of ro…