16 citations · 96 across the 45 of their papers we have counts for
4 papers · 2 filters
Non-commutativity of exponential spectrum
Hubert Klaja, Thomas Ransford
In a Banach algebra, the spectrum satisfies for each pair of elements . We show that this is no longer true for the exponential spe…
On mapping theorems for numerical range
Hubert Klaja, Javad Mashreghi, Thomas Ransford
Let be an operator on a Hilbert space with numerical radius . According to a theorem of Berger and Stampfli, if is a function in the disk algebra such that $f…
A Gleason-Kahane-Żelazko theorem for modules and applications to holomorphic function spaces
Javad Mashreghi, Thomas Ransford
We generalize the Gleason-Kahane-Żelazko theorem to modules. As an application, we show that every linear functional on a Hardy space that is non-zero on outer functions is a multi…
Constructive approximation in de Branges-Rovnyak spaces
O. El-Fallah, E. Fricain, K. Kellay +2
In most classical holomorphic function spaces on the unit disk, a function can be approximated in the norm of the space by its dilates $f\_r(z):=f(rz)~(r \textless{} 1)$. We sh…