Truncations of multilinear Hankel operators

We extend to multilinear Hankel operators the fact that some truncations of bounded Hankel operators are still bounded. We prove and use a continuity property of bilinear Hilbert transforms on products of Lipschitz spaces and Hardy spaces.

     

On compact extensions of multilinear operators

In this paper we prove that, under certain conditions, Nicodemi extensions of compact multilinear operators between Banach spaces are compact as well. An application of this result to the isometric/isomorphic theory of spaces of compact multilinear operators is provided.     

Representations of completely decomposable rings

A criterion is given for finiteness of the number of nonisomorphic nondecomposable representations for the completely decomposable orders over a complete local Dedekind ring which comprise an intersection of maximal orders.Translated from Matematicheskie Zametki, Vol. 3, No. 6, pp. 643–650, June, 1968.In conclusion the authors extend their utmost appreciation to all those participating in the seminar on representation theory at the Institute of Mathematics of the Academy of Sciences of the Ukrainian SSR for their continued interest and valuable suggestions toward the completion of this paper.     

Triebel-lizorkin space estimates for multilinear operators of sublinear operators

In this paper, we obtain the continuity for some multilinear operators related to certain non-convolution operators on the Triebel-Lizorkin space. The operators include Littlewood-Paley operator and Marcinkiewicz operator.     

CBMO estimates for multilinear Hardy operators

The purpose of this paper is to study the multilinear Hardy operators in higher dimensional cases and establish the CBMO estimates for multilinear Hardy operators on some function spaces, such as the Lebesgue spaces, the Herz spaces and the Morrey-Herz spaces.     

Representations of bounded harmonic functions

Summary An open subsetD ofR ^d ,d≧2, is called Poissonian iff every bounded harmonic function on the set is a Poisson integral of a bounded function on its boundary. We show that the intersection of two Poissonian open sets is itself Poissonian and give a sufficient condition for the union of two Poissonian open sets to be Poissonian. Some necessary and sufficient conditions for an open set to be Poissonian are also given. In particular, we give a necessary and sufficient condition for a GreenianD to be Poissonian in terms of its Martin boundary. Supported by NSF DMS86-01800.     

Strongly p-summing multilinear operators

We define the concept of strongly p-summing multilinear operators and prove that they have properly defined Aron-Berner extensions. Some properties and examples are shown.     

Completely continuous and related multilinear operators

Completely continuous multilinear operators are defined and their properties investigated. This class of operators is shown to form a closed multi-ideal. Unlike the linear case, compact multilinear operators need not be completely continuous. The completely continuous maps are shown to be the closure of a subspace of the finite rank operators. Hilbert-Schmidt operators are also considered. An application to finding error bounds for solutions of multipower equations is presented.     

Weighted estimates for multilinear pseudodifferential operators

In this paper,we study the weighted estimates for multilinear pseudodifferential operators.We show that a multilinear pseudodifferential operator is bounded with respect to multiple weights whenever its symbol satisfies some smoothness and decay conditions.Our result generalizes similar ones from the classical Ap weights to multiple weights.     

多线性分数次积分算子的一致有界性

研究了Lebesgue空间上多线性分数次积分算子和相应的多线性分数次极大算子的有界性,利用多线性分数次积分转化为相对应的分数次积分的方法来讨论,得到算子TΩ,α,A1,A2和MΩ,α,A1,A2的(Lp,Lq)的一致L ipsch itz估计,获得一种简明的方法.     

Techniques to generate hyper-ideals of multilinear operators

The usual techniques to generate ideals of multilinear operators between Banach spaces fail in generating hyper-ideals in general. In this paper, we fill this gap by developing two techniques to generate hyper-ideals of multilinear operators. The techniques we develop generate new classes of multilinear operators and show that some important well-studied classes are Banach or p-Banach hyper-ideals.     

On completely irreducible operators

Let T be a bounded linear operator on Hilbert space H, M an invariant subspace of T. If there exists another invariant subspace N of T such that H = M + N and M ∩ N = 0, then M is said to be a completely reduced subspace of T. If T has a nontrivial completely reduced subspace, then T is said to be completely reducible; otherwise T is said to be completely irreducible. In the present paper we briefly sum up works on completely irreducible operators that have been done by the Functional Analysis Seminar of Jilin University in the past ten years and more. The paper contains four sections. In section 1 the background of completely irreducible operators is given in detail. Section 2 shows which operator in some well-known classes of operators, for example, weighted shifts, Toeplitz operators, etc., is completely irreducible. In section 3 it is proved that every bounded linear operator on the Hilbert space can be approximated by the finite direct sum of completely irreducible operators. It is clear that a completely irreducible operator is a rather suitable analogue of Jordan blocks in L(H), the set of all bounded linear operators on Hilbert space H. In section 4 several questions concerning completely irreducible operators are discussed and it is shown that some properties of completely irreducible operators are different from properties of unicellular operators. __________ Translated from Acta Sci. Nat. Univ. Jilin, 1992, (4): 20–29     

On completely hyperexpansive operators

We introduce and discuss a class of operators, to be referred to as the class of completely hyperexpansive operators, which is in some sense antithetical to the class of contractive subnormals. The new class is intimately related to the theory of negative definite functions on abelian semigroups. The known interplay between positive and negative definite functions from the theory of harmonic analysis on semigroups can be exploited to reveal some interesting connections between subnormals and completely hyperexpansive operators.

     

Representations of invariant multilinear maps on HilbertC*-modules

The definition of a completely positive invariant multilinear map from aC*-algebra to another is introduced. We construct the representation of a completely positive invariant multilinear map on a HilbertC*-module without the bridging maps. This is another extension of the Stinespring’s representation, which is different from a multilinear representation of Christensen and Sinclair. We give the covariant representation of completely positive invariant covariant multilinear maps on a HilbertC*-module. Further, we investigate the order structure of such maps and obtain a generalization of the Radon-Nikodym theorem. Partially supported by GARC-KOSEF.