Several variable spectral theory in the noncommutative case
Shapes and computer generation of numerical ranges of Krein space operators.
Some Berezin number inequalities for operator matrices
Some properties of composition operators on the Dirichlet space.
Spatial numerical range of operators on weighted Hardy spaces.
Spectra and Numerical Ranges in Locally M-Convex Algebras
Spectral theory and Cauchy problems on Lp spaces.
Spectraloid operator polynomials, the approximate numerical range and an Eneström-Kakeya theorem in Hilbert space
We study a class of operator polynomials in Hilbert space which are spectraloid in the sense that spectral radius and numerical radius coincide. The focus is on the spectrum in the boundary of the numerical range. As an application, the Eneström-Kakeya-Hurwitz theorem on zeros of real polynomials is generalized to Hilbert space.
Sums of idempotents and a lemma of N. J. Kalton
A lemma of Gelfand-Hille type is proved. It is used to give an improved version of a result of Kalton on sums of idempotents.