Commutators of n-dimensional rough Hardy operators

In this paper, we study central BMO estimates for commutators of n-dimensional rough Hardy operators. Furthermore, λ-central BMO estimates for commutators on central Morrey spaces are discussed.     

Best constants for Hausdorf operators on n-dimensional product spaces

In this paper,we study certain Hausdorf operators in the high-dimensional product spaces.We obtain their power weighted boundedness from Lpto Lqand characterize the necessary and sufcient conditions for their boundedness on the power weighted Lpspaces.Moreover,in the case p=q,we obtain the sharp bound constants.     

Convolution operators on Lebesgue spaces of an n-dimensional cube

This paper is concerned with the problem of diagonally scaling a given nonnegative matrix a to one with prescribed row and column sums. The approach is to represent one of the two scaling matrices as the solution of a variational problem. This leads in a natural way to necessary and sufficient conditions on the zero pattern of a so that such a scaling exists. In addition the convergence of the successive prescribed row and column sum normalizations is established. Certain invariants under diagonal scaling are used to actually compute the desired scaled matrix, and examples are provided. Finally, at the end of the paper, a discussion of infinite systems is presented.     

Best constants for Hausdorff operators on n-dimensional product spaces

In this paper, we study some new kinds of Hausdorff operators on n-dimensional product spaces. We obtain their power weights from L ^p to L ^q boundedness and characterize the necessary and sufficient conditions for the operators being bounded on power weight L ^p spaces. Moreover, we get the sharp constants for the case p = q.     

Characterization for commutators of n-dimensional fractional Hardy operators

In this paper, it was proved that the commutator Hβ,b generated by an n-dimensional fractional Hardy operator and a locally integrable function b is bounded from Lp1(Rn) to Lp2 (Rn) if and only if b is a C(M)O(Rn) function, where 1/p1 - 1/p2 = β/n, 1 ＜ p1 ＜∞, 0 ≤β＜ n. Furthemore,the characterization of Hβ,b on the homogenous Herz space (K)qα,p(Rn) was obtained.     

Growth of certain harmonic functions in an n-dimensional cone

We give the growth properties of harmonic functions at infinity in a cone, which generalize the results obtained by Siegel-Talvila.     

Positive operators on operator algebras

Si dimostra la debole compattezza delle applicazioni lineari positive dalla parte autoaggiunta di un'algebra di von Neumann su uno spazio di Banach parzialmente ordinato, separabile, normale.     

Positive operators on Krein spaces

A Krein operator is a positive operator, acting on a partially ordered Banach space, that carries positive elements to strong units. The purpose of this paper is to present a survey of the remarkable spectral properties (most of which were established by M.G. Krein) of these operators. The proofs presented here seem to be simpler than the ones existing in the literature. Some new results are also obtained. For instance, it is shown that every positive operator on a Krein space which is not a multiple of the identity operator has a nontrivial hyperinvariant subspace. Dedicated to the memory of M.G. Krein (1907–1989)     

Endpoint estimates for n-dimensional Hardy operators and their commutators

In this paper,the sharp bound for the weak-type(1,1) inequality for the n-dimensional Hardy operator is obtained.Moreover,the precise norms of generalized Hardy operators on the type of Campanato spaces are worked out.As applications,the corresponding norms of the Riemann-Liouville integral operator and the n-dimensional Hardy operator are deduced.It is also proved that the n-dimensional Hardy operator maps from the Hardy space into the Lebesgue space.The endpoint estimate for the commutator generated by the Hardy operator and the(central) BMO function is also discussed.     

Resolvents of elliptic cone operators

We prove the existence of sectors of minimal growth for general closed extensions of elliptic cone operators under natural ellipticity conditions. This is achieved by the construction of a suitable parametrix and reduction to the boundary. Special attention is devoted to the clarification of the analytic structure of the resolvent.     

Boundedness of quasilinear integral operators on the cone of monotone functions

We study the problem of characterizing weighted inequalities on Lebesgue cones of monotone functions on the half-axis for one class of quasilinear integral operators.     

Two-sided estimates for matrix operators on the cone of monotone sequences

Weighted estimates for a class of non-negative lower triangular matrices have been established on the cone of monotone sequences.