Some results on b-AM-compact operators

We show that for positive operator B : E → E on Banach lattices, if there exists a positive operator S : E → E such that:1.SB ≤ BS;2.S is quasinilpotent at some x₀ > 0; 3.S dominates a non-zero b-AM-compact operator, then B has a non-trivial closed invariant subspace. Also, we prove that for two commuting non-zero positive operators on Banach lattices, if one of them is quasinilpotent at a non-zero positive vector and the other dominates a non-zero b-AM-compact operator, then both of them have a common non-trivial closed invariant ideal. Then we introduce the class of b-AM-compact-friendly operators and show that a non-zero positive b-AM- compact-friendly operator which is quasinilpotent at some x₀ > 0 has a non-trivial closed invariant ideal.     

Some approximation results for Durrmeyer operators

In the present paper, we obtain a sequence of positive linear operators which has a better rate of convergence than the Szász-Mirakian Durrmeyer and Baskakov Durrmeyer operators and their Voronovskaya type results.     

Some summability properties of operators on a separable Banach space

Archiv der Mathematik -     

Some eigenvalue results for maximal monotone operators

We study the eigenvalue problem of the form

0∈Tx−λCx,     

Some results about operators on L1

Let (Ω, Σ, µ) be a probability space. We give a few results about operators on L₁(µ). Among these, we show that if T is a bounded linear operator on L₁(µ) which acts as a Hilbert-Schmidt operator on L₂(µ), then T : L₁(µ) → L₁(µ) is representable.     

Some results on modified Szász-Mirakjan operators

In this paper we study the mixed summation-integral type operators having Szász and Beta basis functions. We extend the study of Gupta and Noor [V. Gupta, M.A. Noor, Convergence of derivatives for certain mixed Szász-Beta operators, J. Math. Anal. Appl. 321 (1) (2006) 1-9] and obtain some direct results in local approximation without and with iterative combinations. In the last section are established direct global approximation theorems.     

Some fixed point results on a metric space with a graph

Combining some branches is a typical activity in different fields of science, especially in mathematics. Naturally, it is notable in fixed point theory. Over the past few decades, there have been a lot of activity in fixed point theory and another branches in mathematics such differential equations, geometry and algebraic topology. In 2006, Espinola and Kirk made a useful contribution on combining fixed point theory and graph theory. Recently, Reich and Zaslavski studied a new inexact iterative scheme for fixed points of contractive and nonexpansive multifunctions. In this paper, by using main idea of their work and the idea of combining fixed point theory and graph theory, we present some iterative scheme results for G-contractive and G-nonexpansive mappings on graphs.     

Some classes of operators with symbol on the Lipschitz space of a tree

In this paper, we expand the study of the multiplication operators on the Lipschitz space of a tree begun in Colonna and Easley (Integral Equ Oper Theory 68:391–411, 2010) by focusing on their adjoint acting on a certain separable subspace of the Lipschitz space whose dual is isometrically isomorphic to \(\mathbf L^1\). We then study the properties of two useful operators \(\nabla \) and \(\Delta \) and use them (along with the multiplicative symbol \(\psi \)) to define the Toeplitz operator \(T_\psi \) on the space \(\mathbf L^p\) for \(1\le p \le \infty \). We give conditions for its boundedness and study its point spectrum.     

Some new results on the class of AM-compact operators

We establish some new necessary and sufficient conditions under which each regular operator is AM-compact if and only if its adjoint is AM-compact. Also, we give some consequences.     

Some results concerning normal r- potent operators

In this note it will be shown that a normal operator A which satisfies the equation p(A)=0. where p is a polynomial, can be diagonalized. Next, an equivalent characterisation of a normal r-potent operator and some othci basic properties oi normal r-potent operators will he given Included will be a generalization of the algebraic version of Cochran's statistical theorem concerning quadratic forms.     

Some thoughts on composition operators on subspaces of the Hardy space

Archiv der Mathematik - We discuss composition operators on certain subspaces of the Hardy space. The family of subspaces that we deal with are called $$H^2_{alpha , beta }$$ which have garnered...     

Some spectral properties of a bundle of linear operators in Banach space

The spectral properties of a bunchA–B, D(A)D(B), of linear closed densely defined operators in Banach space are considered. Our main result is a theorem to the effect that the spectrum of the bunch can be expanded with respect to a pair of direct sums; the theorem generalizes the celebrated theorem of Riesz concerning the expansion of the spectrum of an operator.Translated from Matematicheskie Zametki, Vol. 22, No. 6, pp. 847–857, December, 1977.