4 citations · 4 across the 6 of their papers we have counts for
7 papers
Dilation Theory for Scaled -Numerical Ranges
Matias Kaunisto, Ryan O'Loughlin, Jani Virtanen
We generalise Berger's dilation theorem from numerical ranges to scaled -numerical ranges. Specifically, we prove that if the scaled -numerical range is co…
The Complete Crouzeix Conjecture in Dimension Three and the Clouâtre-Ostermann-Ransford conjecture
Per Åhag, Rafał Czyż, Jani Virtanen
We settle the complete Crouzeix conjecture for matrices of order at most three and prove the Q-algebra case of the completely bounded Clouâtre--Ostermann--Ransford (COR) conjecture…
On the abstract approach to spectral constants: a proof of the Clouâtre--Ostermann--Ransford conjecture
Catalin Badea, Ryan O'Loughlin, Jani Virtanen
Clouâtre, Ostermann, and Ransford formulated an abstract version of Crouzeix's conjecture involving a bounded unital homomorphism from a uniform algebra into matrices and a unital…
A Counterexample to the Gau--Wang--Wu Conjecture on Partial Isometries
Ryan O'Loughlin, Jani Virtanen
We disprove the conjecture of Gau, Wang and Wu that the numerical range of a finite-dimensional partial isometry, when circular, must be centred at the origin. More precisely, we p…
Maximal Plurisubharmonic Functions and Fujii-Seo Determinants in Hilbert spaces
Per Åhag, Rafał Czyż, Antti Perälä +1
A maximal plurisubharmonic function on an infinite-dimensional Hilbert space can have an injective, noncompact Levi operator at every point. This raises the question of what replac…
A survey of asymptotics of determinants for structured matrices
E. Basor, T. Ehrhardt, J. A. Virtanen
In this survey we show how to produce asymptotics of determinants of structured matrices using operator theory methods. We describe the asymptotics for finite Toeplitz matrices, fi…
Asymptotics of block Toeplitz determinants with piecewise continuous symbols
E. Basor, T. Ehrhardt, J. A. Virtanen
We determine the asymptotics of the block Toeplitz determinants as for matrix-valued piecewise continuous functions with a finitely many…