Haykel Gaaya

most citedOn the higher rank numerical range of the shift operator

4 citations · 6 across the 3 of their papers we have counts for

collaborators

3 papers

math.FA2012★ 2 cited

On the numerical radius of the truncated adjoint Shift

Haykel Gaaya

A celebrated thorem of Fejer (1915) asserts that for a given positive trigonometric polynomial $\sum_{j = - n + 1}^{n - 1} c_{j} e^{ij t}$ , we have $\lvert c_{1}\lvert\leqslant c_{0}\cos\fra…

math.FA2012

A sharpened Schwarz-Pick operatorial inequality for nilpotent operators

Haykel Gaaya

Let denote by $S (ϕ)$ the extremal operator defined by the compression of the unilateral shift $S$ to the model subspace $H (ϕ) = H^{2} ⊖ ϕ H^{2}$ as the following $S(ϕ)f(z)=P(z…

math.FA2010★ 4 cited

On the higher rank numerical range of the shift operator

Haykel Gaaya

For any n-by-n complex matrix T and any $1 ⩽ k ⩽ n$ , let $Λ_{k} (T)$ the set of all $λ\in \C$ such that $P T P = λ P$ for some rank-k orthogonal projection $P$ be its highe…