34 citations · 34 across the 3 of their papers we have counts for
6 papers
Perturbations of operators similar to contractions and the commutator equation
Catalin Badea
Let and be two Hilbert space contractions and let be a linear bounded operator. It was proved by C. Foias and J.P. Williams that in certain cases the operator block mat…
Constrained von Neumann inequalities
Catalin Badea, Gilles Cassier
An equivalent formulation of the von Neumann inequality states that the backward shift on is extremal, in the sense that if is a Hilbert space contraction, the…
Schur multipliers and operator-valued Foguel-Hankel operators
Catalin Badea, Vern I. Paulsen
We show that some matrices are Schur multipliers and this is applied to obtain classes of operator-valued Foguel-Hankel operators similar to contractions. This provides partial ans…
Operators near completely polynomially dominated ones and similarity problems
C. Badea
Let T and C be two Hilbert space operators. We prove that if T is near, in a certain sense, to an operator completely polynomially dominated with a finite bound by C, then T is sim…
The stability radius of linear operator pencils
C. Badea, M. Mbekhta
Let T and S be two bounded linear operators from Banach spaces X into Y and suppose that T is Fredholm and the stability number k(T;S) is 0. Let d(T;S) be the supremum of all r > 0…
The Stable Rank of Topological Algebras and a Problem of R.G. Swan
C. Badea
Various notions of stable ranks are studied for topological algebras. Some partial answers to R.G. Swan's problem (Have two Banach or good Fréchet algebras as in the density theore…