Herz–Morrey spaces of variable exponent,Riesz potential operator and duality

Our aim in this paper is to deal with the boundedness of the Hardy–Littlewood maximal operator on Herz–Morrey spaces and to establish Sobolev’s inequalities for Riesz potentials of functions in Herz–Morrey spaces. Further, we discuss the associate spaces among Herz–Morrey spaces.     

The Schrödinger operator with a weakly accelerating potential

The ideas of scattering theory are applied to the construction of a unitary operator realizing the similarity of the operator - id/d in L₂() with a one-dimensional Schrödinger operator on the semiaxis with potential v(x), admitting at infinity the estimate.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 147, pp. 10–12, 1985.     

The Riesz–Kantorovich formula for lexicographically ordered spaces

If L and M are partially ordered vector spaces, then one can consider regular linear maps from L to M, i.e. linear maps which can be written as the difference of two positive linear maps. If the space L is directed, then the space \(L^r(L,M)\) of all regular linear operators becomes a partially ordered vector space itself. We will mainly concern ourselves with the questions when the space \(L^r(L,M)\) is itself a Riesz space and how, even if it is not a Riesz space, its lattice operations work. The so-called Riesz–Kantorovich theorem gives sufficient conditions for which \(L^r(L,M)\) is a Riesz space and it also specifies the lattice operations by means of the Riesz–Kantorovich formula: if \(S,T\in L^r(L,M)\) and \(x\in L\) with \(x\ge 0\) then the supremum \(S\vee T\) in the point x is given by

$$\begin{aligned} (S\vee T)(x)=\sup \left\{ S(y)+T(x-y):0\le y\le x\right\} . \end{aligned}$$

It is still an open problem if whenever in a more general setting the supremum of two regular operators exists in \(L^r(L,M)\), it automatically is given by the Riesz–Kantorovich formula. Our main result concerns the special case where L is a partially ordered vector space with a strong order unit and M is a (possibly infinite) product of copies of the real line, equipped with the lexicographic ordering. It will turn out that under some mild continuity and regularity conditions the lattice operations on \(L^r(L,M)\) are indeed given by the Riesz–Kantorovich formula, even though the space \(L^r(L,M)\) is not necessarily a Riesz space.

     

The maximal Fejér operator on real Hardy spaces

We prove that the maximal Fej'er operator is not bounded on the real Hardy spaces H ¹, which may be considered over and . We also draw corollaries for the corresponding Hardy spaces over ² and ². This revised version was published online in August 2006 with corrections to the Cover Date.     

Locating a general minisum ��circle�� on the plane

We approximate a set of given points in the plane by the boundary of a convex and symmetric set which is the unit circle of some norm. This generalizes previous work on the subject which considers Euclidean circles only. More precisely, we examine the problem of locating and scaling the unit circle of some given norm k with respect to given points on the plane such that the sum of weighted distances (as measured by the same norm k) between the circumference of the circle and the points is minimized. We present general results and are able to identify a finite dominating set in the case that k is a polyhedral norm.     

The boundedness of multilinear Calderón–Zygmund operators on Hardy spaces

In this paper, we study the boundedness of the multilinear Calderón–Zygmund operators on products of Hardy spaces.     

The BMO L space and Riesz transforms associated with Schrödinger operators

Let L =△ ＋ V be a SchrSdinger operator in Rd, d ≥ 3, where the nonnegative potential V belongs to the reverse HSlder class Sd. We establish the BMOL-boundedness of Riesz transforms З/ЗxiL-1/2, and give the Fefferman-Stein type decomposition of BMOL functions.     

The generalized Roper-Suffridge extension operator in Banach spaces (Ⅲ)

Suppose that X is a complex Banach space with the norm ||·|| and n is a positive integer with dim X ≥n≥ 2. In this paper,we consider the generalized Roper-Suffridge extension operator Φn,β2,γ2,...,βn+1,γn+1(f) on the domain Ωp1,p2,...,pn+1 defined by     

The function G λ * as the norm of a Calderón-Zygmund operator

We describe a new approach to one of the quadratic functions in the Littlewood-Paley theory, namely, to the function G _λ *. It is shown that some of its properties can be obtained from the general theory of operators of Calderón-Zygmund type (which, apparently, has not been considered applicable in this context). There are applications to interpolation theory.     

Schrödinger operator with a perturbed small steplike potential

We consider the Schrödinger operator with a potential that is periodic with respect to two variables and has the shape of a small step perturbed by a function decreasing with respect to a third variable. We show that under certain conditions on the magnitudes of the step and the perturbation, a unique level that can be an eigenvalue or a resonance exists near the essential spectrum. We find the asymptotic value of this level.     

Quasilevels of a two-particle Schrödinger operator with a perturbed periodic potential

We consider a two-dimensional periodic Schrödinger operator perturbed by the interaction potential of two one-dimensional particles. We prove that quasilevels (i.e., eigenvalues or resonances) of the given operator exist for a fixed quasimomentum and a small perturbation near the band boundaries of the corresponding periodic operator. We study the asymptotic behavior of the quasilevels as the coupling constant goes to zero. We obtain a simple condition for a quasilevel to be an eigenvalue.     

An Andô-Douglas type theorem in Riesz spaces with a conditional expectation

In this paper we formulate and prove analogues of the Hahn-Jordan decomposition and an Andô-Douglas-Radon-Nikodým theorem in Dedekind complete Riesz spaces with a weak order unit, in the presence of a Riesz space conditional expectation operator. As a consequence we can characterize those subspaces of the Riesz space which are ranges of conditional expectation operators commuting with the given conditional expectation operators and which have a larger range space. This provides the first step towards a formulation of Markov processes on Riesz spaces.