arXiv subjects
Publications and source records attributed to M. S. Al Ghafri.
We provide a characterisations of nuclear weighted conditional expectation operators on $L^p(μ)$-spaces, for $1\leq p<\infty$. As a consequence, when the underlying measure space is non-atomic, the only nuclear weighted conditional expectation operator on $L^p(μ)$-spaces is the zero operator.
In this paper we characterize $m$-isometric and quasi-$m$-isometric weighted conditional type (WCT) operators on the Hilbert space $L^2(μ)$. Also, we prove that the subclasses of $m$-isometric and quasi-$m$-isometric of normal WCT operators are coincide. Specially we have the results for multiplication operators. Indeed, we find that for $m\geq 2$, a multiplication operator $M_u$ is $m$-isometric (quasi-$m$-isometric) if and only if it is isometric (quasi-isometric). Some examples are provided to illustrate our results.
In this paper we characterize $m$-isometric and quasi-$m$-isometric weighted composition operators on the Hilbert space $L^2(μ)$. Also, we find that normal-$m$-isometry and normal quasi-$m$-isometry weighted composition operators have finite spectrum. Consequently we have the results for composition and multiplication operators. In addition, we prove that for $m\geq 2$, a multiplication operator is $m$-isometry (quasi-$m$-isometry) if and only if it is $2$-isometry (quasi-$2$-isometry). Some examples are provided to illustrate our results.
This paper investigates composition operators and weighted composition operators on semi-Hilbert spaces induced by positive multiplication operators on \( L^2(μ) \). Within the framework of \( A \)-adjoint operators, we characterize conditions under which a composition operator \( C_φ\) is \( A \)-selfadjoint, \( A \)-normal, \( A \)-quasinormal, or \( A \)-unitary, where \( A = M_u \) denotes a positive multiplication operator. Additionally, we provide necessary and sufficient conditions for \( C_φ\) to be an \( A \)-isometry or an \( A \)-partial isometry. Analogous results are also obtained when \( A \) is a positive composition operator. Several examples are presented to illustrate the applicability of the main results.
In this paper we define $λ$-hyponormal operators on an infinite dimensional Hilbert space $\mathcal{H}$ and find a class of $λ$-hyponormal operators that can not be hypercyclic. Also, we study closedness of range and $λ$-hyponormality of weighted composition operators on the Hilbert space $\mathcal{H}=L^2(μ)$. Moreover, we apply the hypercyclicity results to $λ$-hyponormal weighted composition operators. Finally, we provide some examples to illustrate our main results.
The objective of this paper is to find an estimation of the essential norm of Riemann-Stieltjes operator from the spaces $F(p,q,s)$ ( general function space) and $H(p,q,ϕ)$ (mixed-norm space) into Zygmund-type space in the unit ball of $\mathbb{C}^n$.
In this paper, we consider the generalized integration operator from mixed-norm space into Zygmund-type and Bloch-type spaces and find an estimation for the essential norm of this operator.