34 citations · 102 across the 28 of their papers we have counts for
36 papers
Iterates of Ritt operators close to the identity
Catalin Badea
We study bounded operators whose prescribed powers remain uniformly close to the identity, and resolvent conditions sampled along sequences of powers. The displacement bound $\sup_…
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 note on the Huijsmans-de Pagter problem on finite dimensional ordered vector spaces
Catalin Badea, Jochen Glück
A classical problem posed in 1992 by Huijsmans and de Pagter asks whether, for every positive operator on a Banach lattice with spectrum , the inequality $T \ge \…
Schwarz-Pick type inequalities from an operator theoretical point of view
Catalin Badea, Axel Renard
We use (versions of) the von Neumann inequality for Hilbert space contractions to prove several Schwarz-Pick inequalities. Specifically, we derive an alternate proof for a multi-po…
Around Furstenberg's times , times conjecture: times -invariant measures with some large Fourier coefficients
Catalin Badea, Sophie Grivaux
For each integer , denote by the map from the circle group into itself. Let be two multiplicativ…
Rochberg's abstract coboundary theorem revisited
Catalin Badea, Oscar Devys
Rochberg's coboundary theorem provides conditions under which the equation is solvable in . Here is a unilateral shift on Hilbert space, is the identity ope…