C. Badea

activity

19982005

most citedConstrained von Neumann inequalities

34 citations · 34 across the 3 of their papers we have counts for

collaborators

Showing math.FAShow all

5 papers · 1 filter

math.FA2005

Perturbations of operators similar to contractions and the commutator equation

Catalin Badea

Let $T$ and $V$ be two Hilbert space contractions and let $X$ be a linear bounded operator. It was proved by C. Foias and J.P. Williams that in certain cases the operator block mat…

math.FA2005★ 34 cited

Constrained von Neumann inequalities

Catalin Badea, Gilles Cassier

An equivalent formulation of the von Neumann inequality states that the backward shift $S^{*}$ on $ℓ_{2}$ is extremal, in the sense that if $T$ is a Hilbert space contraction, the…

math.FA2005

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…

math.FA2001

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…

math.FA2000

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…