# Bahmann YousefiPayame Noor University and Shiraz University

Bahmann Yousefi

Professor of Mathematics

## About

161

Publications

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1,114

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Introduction

**Skills and Expertise**

## Publications

Publications (161)

Following the recent work done in [27], we give various other conditions to ensure that the powers of the multiplication operator Mz are reflexive on a Banach space X of functions analytic on a plane domain. Also, some examples of function spaces satisfying the given conditions are considered.

In this paper, the [Formula: see text]-radius stability of a matrix polynomial [Formula: see text] relative to a domain [Formula: see text] of the complex plane and its relation with the [Formula: see text]-numerical range of [Formula: see text] are investigated. By using an expression of the [Formula: see text]-radius stability, we obtain a lower...

In this paper, we introduce subspace hypercyclicity and transitivity of tuples of operators and we give some relations between these concepts and the subspace transitivity criterion for a tuple of operators.

In this paper, we introduce subspace hypercyclicity and transitivity of tuples of operators and we give some relations between these concepts and the subspace transitivity criterion for a tuple of operators.

In the present paper we investigate conditions under which a parabolic self-map of the open unit disk induces a hypercyclic weighted composition operator in some Banach function spaces.

In the present paper we investigate conditions under which a hyperbolic self-map of the open unit disk induces a hypercyclic weighted composition operator in the space of holomorphic functions on the unit ball in CN.

In this paper we investigate the hypercyclicity of adjoint of a special weighted composition operators on a Banach function space.

In this paper we prove the Hyers-Ulam stability of n -ary Lie homomorphisms on n-ary Lie Banach algebras associated to a generalized functional equation.

In this paper we investigate the hypercyclicity of adjoint of a special weighted composition operators on Hilbert spaces of analytic functions on the open unit disc.

In this paper we give some sufficient conditions for the adjoint of a combination of weighted composition operators, acting on some function spaces, satisfying the hypercyclicity criterion.

In this paper we prove the Hyers-Ulam stability of special homomorphisms on some Banach algebras associated to a generalized functional equation.

We will investigate the cyclicity for the adjoint of a weighted composition operator acting on (lp(α))∗.

In this paper, we give some sufficient conditions for cyclicity of adjoint of the multiplication operator acting on a space of formal power series with coefficients in some BK spaces with BK property.

In this paper, first we give conditions under which the weighted mean matrix operator is bounded on the weighted Hardy spaces, and we characterize the spectrum of the weighted mean matrix operator acting on some sequence spaces. Then we investigate eigenvectors of weighted mean matrix operator.

In this paper, we give a criterion under which a tuple being countably subspace-hypercyclic.

In this paper we investigate the conditions under which a tuple of operator holds in the subspace-transitivity criterion.

In this paper, we investigate subspace supercyclicity of tuples of operators.

In this paper, we extend some results of Banach algebras concerning the radical and spectral properties to the fundamental locally multiplicative topological algebras (FLM algebras).

Let
Ω
be a complex domain and let
F
be a reflexive BK space with AK such that
F
^
⊂
H
(
Ω
)
and the functional of evaluation at
λ
is bounded for all
λ
∈
Ω
. We will investigate the cyclicity for the adjoint of a weighted composition operator acting on
F
^
.

A matrix A is called reflexive if and only if Lat(A) ⊆ Lat(B) implies that B = p(A) for some polynomial p. In this article, we characterize reflexive non-derogatory matrices.

In this paper, we will show that the spaces of p-bounded variation sequences are AMNM.

In this paper we prove that if a tuple of operators is ε-supercyclic for all ε > 0, then it is supercyclic.

In this paper we state and prove equivalent conditions for a tuple of operators satisfying the supercyclicity criterion.

In this paper, the q-radius stability of a matrix polynomial P(λ) relative to an open region Ω of the complex plane and its relation to the q-numerical range of P(A) are investigated. Also, we obtain a lower bound that involves the distance of Ω to the connected components of the q-numerical range of P(λ).

Let Ω be a complex domain and F̂ be a Banach space of formal power series with coefficients in a reflexive BK space with AK such that F̂ ⊂ H(Ω) and the functional of evaluation at λ is bounded for all λ ∈ Ω. We give sufficient conditions for the multiplication operator M̂z to be reflexive on F̂.

Let Mφ be the operator of multiplication by φ on a Hilbert space of functions analytic on the open unit disk. For an invariant subspace F for the multiplication operator Mz, we derive some spectral properties of the multiplication operator Mφ : F → F. We characterize norm, spectrum, essential norm and essential spectrum of such operators when F has...

In this paper, we give some conditions for a weighted composition operator in the space of analytic functions on a region of the plane domain have an eigenvalue.

In this paper, we give sufficient conditions for a tuple of operators to be supercyclic.

In this paper we give conditions under which a tuple of commutative bounded linear operators, acting on a Banach space, satisfying the property of topologically mixing.

In this paper, we give conditions under which a tuple of operators satisfies the Hypercyclicity Criterion.

In terms of open sets, we give necessary and sufficient conditions under which the set of some direct sums in the semigroup generated by a tuple of operators is hypercyclic.

We prove that the set of some direct sums in the semigroup generated by a tuple of operators is hypercyclic if and only if the tuple satisfies the hypercyclicity criterion.

In this paper we prove that topologically mixing is equivalent to the hypercyclicity criterion for a tuple of commutative bounded linear operators. Also, we investigate some other equivalent conditions for a tuple satisfying the hypercyclicity criterion.

In this paper, we characterize some necessary and sufficient conditions for a tuple of operators to be hereditarily hypercyclic.

In this paper we present sufficient conditions for reflexivity of any powers of the multiplication operator acting on Banach spaces of formal Laurent series.

In this paper we give necessary and sufficient conditions under which a tuple of operators satisfying the conditions of Hypercyclicity Criterion.

The aim of the paper is to propose a definition of numerical range of an operator on reflexive Banach spaces. Under this definition the numerical range will possess the basic properties of a canonical numerical range. We will determine necessary and sufficient conditions under which the numerical range of a composition operator on a weighted Hardy...

We investigate the boundedness and the compactness of the
mean operator matrix acting on the weighted Hardy spaces.

In this paper we characterize necessary and sufficient conditions for a tuple of operators satisfying the conditions of Hypercyclicity Criterion.

Let T = (T 1 , T 2 , ..., T n) be an n-tuple of operators acting on an infinite dimensional Banach space X. In this paper we want to give necessary and sufficient conditions for T being syndetically hypercyclic tuple.

In this paper, we characterize the conditions under which a tuple of bounded linear operators is topologically mixing. Also, we give conditions for a tuple to be hereditarily hypercyclic with respect to a tuple of syndetic sequences.

In this paper we characterize the equivalent conditions for a tuple of commutative bounded linear operators, satisfying the hypercyclicity criterion.

In this paper we characterize the equivalent conditions for a tuple of commutative bounded linear operators, satisfying the hypercyclicity criterion.

In this paper we characterize conditions for a tuple of operators satisfying the Hypercyclicity criterion.

We present sufficient conditions for reflexivity of any powers of the multiplication operator acting on Banach spaces of formal Laurent series, whenever it is not invertible.

In this paper we characterize the equivalent conditions for a tuple of commutative bounded linear operators, satisfying the hypercyclicity criterion.

Let ψ be analytic on the open unit disk U and φ be an analytic self-map on U. The weighted composition operator C ψ,φ on a Hilbert space H of analytic functions on U is given by (C ψ,φ f)(z)=φ(z)f(ψ(z)). This paper discusses the adjoint of weighted composition operators (C ψ,φ * ) acting on the Hardy, Bergman and Dirichlet spaces.

In this paper we prove an iteration procedure in cone metric spaces.

In this paper we give necessary conditions for the semistability of an iteration procedure in cone metric spaces.

In this paper we characterize the dual space of formal power series and then we investigate cyclicity of the multiplication operator.

In this paper we characterize the eigenfunctions of weighted composition operators acting on Hilbert spaces of analytic functions.

Let (X,d) be a cone metric space and T be a self-map of X. In this paper we investigate the convergence of an iteration procedure involving T to a fixed point of T.

This paper characterizes some sufficient conditions for a vector in a Hilbert space, with special reproducing kernel, to be cyclic for the multiplication operator.

In this paper we investigate hypercyclicity, supercyclicity and cyclic-ity criterions for a tuple of operators.

In this paper, we characterize conditions under which a tuple of continuous operators is hereditarily transitive. Also, we
investigate the relation between hypercyclicity and d-dense orbits of a tuple of operators.
KeywordsTuple–Topologically transitive–Hereditarily transitive–Topologically mixing–d-dense orbit

The aim of this work is to prove some iteration procedures in cone metric spaces. This extends some recent results of T-stability.
Mathematics Subject Classification
47J25; 26A18.

In this paper we prove that if a pair of operators is �-
hypercyclic for all � > 0, then it is topologically transitive

In this article, we will give sufficient conditions for the boundedness of the analytic projection on the set of multipliers
of the formal Laurent series spaces. This answers a question that has been raised by A. L. Shields. Also, we will characterize
the fixed points of some weighted composition operators acting on weighted Hardy spaces.
AMS Subj...

This article derives the relation between universal interpolating sequences and some spectral properties of the multiplication operator by the independent variable z in case the underlying space is a Hilbert space of functions analytic on the open unit disk.

We consider an equivalent condition to the property
of Supercyclicity Criterion, and then we investigate this property for the adjoint of weighted composition operators acting on Hilbert spaces of analytic functions.

Suppose that ${X}$ is a separable normed space and the operators $A$ and $Q$ are bounded on ${X}$ . In this paper, it is shown that if $AQ=QA$, $A$ is an isometry, and $Q$ is a nilpotent then the operator $A+Q$ is neither supercyclic nor weakly hypercyclic. Moreover, if the
underlying space is a Hilbert space and $A$ is a co-isometric operator, the...

In this paper, we give some sufficient conditions for the adjoint of a weighted composition operator on some function spaces to be hereditarily hypercyclic.

We define an operator on Banach spaces of formal power series and then we give a condition under which it is bounded.

In this paper we characterize the eigenfunctions of certain weighted composition operators C ϕ,ψ acting on Hilbert spaces of analytic functions where ψ is of hyperbolic type and ϕ is nonzero on the Denjoy-Wolff point of ψ.

In this paper we will give some necessary and sufficient conditions for a pair of operators to be Hereditarily.

We give sufficient conditions for the boundedness of the
analytic projection on the set of multipliers of the Banach weighted
Hardy spaces. This presents the sufficient conditions to a problem that
has considered by A. L. Shields.

We give some sufficient conditions for the adjoint of a weighted composition operator to satisfy the supercyclicity criterion on some function spaces.

In this paper we give some sufficient conditions for the adjoint of the multiple weighted composition operators acting on some function spaces satisfying the Supercyclicity Criterion.

We characterize some conditions for a vector to be cyclic for the adjoint of the weighted composition operator acting on the weighted Hardy spaces.

Let F be a topological vector space and T 1 , T 2 be two continuous maps on F , and T = (T 1 , T 2) be a pair of operators. In this paper we want to give necessary and sufficient conditions for T being syndetically hypercyclic pair.

In this paper we will give sufficient conditions for the multipliction operator M z to be reflexive on the weighted Hardy spaces.

We characterize the conditions for a tuple of commutative bounded linear operators on a Fréchet space to satisfy the topologically mixing property.

We give sufficient conditions for the multiplication operator M z to be reflexive on special sequence spaces.

In the present paper we investigate the hypercyclicity of the adjoint of weighted composition operator in special function
spaces.

Let X be a reflexive Banach space of functions analytic on a bounded plane domain G such that for every λ in G the functional of evaluation at λ is bounded. Assume further that X contains the constants and admits multiplication by the independent variable z, M z , as a bounded operator. We give sufficient conditions for M z to be reflexive.

We give sufficient conditions on a domain Ω so that the associated canonical model is reflexive. Also, we discuss a class of shifts that are reflexive, and the operator M z of multiplication by z on a Banach space of functions analytic on a domain is shown to be reflexive whenever M z is polynomially bounded.

We investigate conditions under which a weighted composition operator C ϕ,ψ in the space of analytic functions on a plane domain has an eigenvalue in Ranϕ and we study the hypercyclicity of the adjoint of C ϕ,ψ .

Under some conditions on a Hilbert space $H$ of analytic functions on the open unit disc we will show that for every nontrivial invariant subspace $\mathcal{M}$ of $H$, there exists a unique nonconstant inner function $\varphi$ such that $\mathcal{M}=\varphi H$. This extends the Beurling’s Theorem.

Let B(X) be the operator algebra for a separable infinite dimensional Hilbert space H, endowed with the strong operator topology or *-strong topology. We give sufficient conditions for a continuous linear mapping
L: B(X) → B(X) to be supercyclic or *-supercyclic. In particular our condition implies the existence of an infinite dimensional subspace...

We characterize some sufficient conditions for a vector in the Hilbert spaces of analytic functions to be cyclic for the backward shift operator.

We characterize the hypercyclicity of the composition operator acting on some function spaces of analytic functions.

In this paper we investigate the necessary and sufficient conditions on a symbol ϕ for the boundedness, compactness and hypercyclicity of the induced composition operator C ϕ acting between the weighted Hardy spaces H p (β 1) and H q (β 2), for 1 < q ≤ p < ∞. Also, under the condition of compactness for C ϕ we investigate the fixed points of C ϕ .