S. Noor

activity

20122020

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7 papers · 1 filter

math.FA2024

Beurling and Model subspaces invariant under a universal operator

Ben Hur Eidt, S. Waleed Noor

In this article, we characterize the Beurling and Model subspaces of the Hardy-Hilbert space $H^{2} (D)$ invariant under the composition operator $C_{ϕ_{a}} f = f \circ ϕ_{a}$ , where…

math.FA2023

Minimal invariant subspaces for an affine composition operator

João R. Carmo, Ben Hur Eidt, S. Waleed Noor

The composition operator $C_{ϕ_{a}} f = f \circ ϕ_{a}$ on the Hardy-Hilbert space $H^{2} (D)$ with affine symbol $ϕ_{a} (z) = a z + 1 - a$ and $0 < a < 1$ has the property that the Invariant Subspa…

math.FA2020

Interplay between complex symmetry and Koenigs eigenfunctions

S. Waleed Noor, Osmar R. Severiano

We investigate the relationship between the complex symmetry of composition operators $C_{ϕ} f = f \circ ϕ$ induced on the classical Hardy space $H^{2} (D)$ by an analytic self-map…

math.FA2020

Universal Toeplitz operators on the Hardy space over the polydisk

Marcos Ferreira, S. Waleed Noor

The Invariant Subspace Problem (ISP) for Hilbert spaces asks if every bounded linear operator has a non-trivial closed invariant subspace. Due to the existence of universal operato…

math.FA2019

Universal composition operators

João R. Carmo, S. Waleed Noor

A Hilbert space operator $U$ is called universal (in the sense of Rota) if every Hilbert space operator is similar to a multiple of $U$ restricted to one of its invariant subspaces…