A predual of a predual of <Emphasis Type="Italic">B</Emphasis><Subscript><Emphasis Type="Italic">σ</Emphasis></Subscript> and its applications to commutators

A predual of B_σ-spaces is investigated. A predual of a predual of B_σ-spaces is also investigated, which can be used to investigate the boundedness property of the commutators. The relation between Herz spaces and local Morrey spaces is discussed. As an application of the duality results, one obtains the boundedness of the singular integral operators, the Hardy-Littlewood maximal operators and the fractional integral operators, as well as the commutators generated by the bounded mean oscillation (BMO) and the singular integral operators. What is new in this paper is that we do not have to depend on the specific structure of the operators. The results on the boundedness of operators are formulated in terms of ?_σ-spaces and B_σ-spaces together with the detailed comparison of the ones in Herz spaces and local Morrey spaces. Another application is the nonsmooth atomic decomposition adapted to B_σ-spaces.     

Weighted Oscillation and Variation Inequalities for Singular Integrals and Commutators Satisfying Hrmander Type Conditions

This paper is devoted to investigating the weighted L~p-mapping properties of oscillation and variation operators related to the families of singular integrals and their commutators in higher dimension. We establish the weighted type(p, p) estimates for 1 p ∞ and the weighted weak type(1,1) estimate for the oscillation and variation operators of singular integrals with kernels satisfying certain Hormander type conditions, which contain the Riesz transforms, singular integrals with more general homogeneous kernels satisfying the Lipschitz conditions and the classical Dini's conditions as model examples. Meanwhile, we also obtain the weighted L~p-boundeness for such operators associated to the family of commutators generated by the singular integrals above with BMO(R~d)-functions.     

Characterization of Lipschitz Functions via the Commutators of Singular and Fractional Integral Operators in Variable Lebesgue Spaces

We obtain characterizations of a variable version of Lipschitz spaces in terms of the boundedness of commutators of Calderón-Zygmund and fractional type operators in the context of the variable exponent Lebesgue spaces L ^p(?), where the symbols of the commutators belong to the Lipschitz spaces. A useful tool is a pointwise estimate involving the sharp maximal operator of the commutator and certain associated maximal operators, which is new even in the classical context. Some boundedness properties of the commutators between Lebesgue and Lipschitz spaces in the variable context are also proved.     

Commutators of homogeneous fractional integrals on Herz-type Hardy spaces with variable exponent

Let Ω ∈ L ^s (S ^n?1), s ≥ 1, be a homogeneous function of degree zero, and let σ (0 < σ < n) and b be Lipschitz or BMO functions. In this paper, we establish the boundedness of the commutators [b, T _Ω,σ ], generated by a homogeneous fractional integral operator T _Ω,σ and function b, on the Herz-type Hardy spaces with variable exponent.     

Weighted boundedness of some integral operators on weighted <Emphasis Type="Italic">λ</Emphasis>- central Morrey space

In this paper, the authors prove the weighted boundedness of singular integral and fractional integral with a rough kernel on the weighted λ-central Morrey space. Moreover, the weighted estimate for commutators of singular integral with a rough kernel on the weighted λ-central Morrey space is also given.     

Weighted estimates for commutators of singular integral operators with non-smooth kernels

In this paper, we establish the boundedness of commutators of singular integral operators with non-smooth kernels on weighted Lipschitz spaces Lipβ,ω. The condition on the kernel in this paper is weaker than the usual pointwise H¨ormander condition.     

Weighted Norm Inequalities for Spectral Multipliers on Graphs

Let Γ be a graph endowed with a reversible Markov kernel p, whose associated operator P is defined by \(Pf(x) = {\sum }_{y} p(x, y)f(y)\). We assume that the kernels p_n(x, y) associated to Pⁿ satisfy Gaussian upper bounds but do not assume they satisfy the Hölder continuity property and the temporal regularity. Denote by L = I ? P the discrete Laplacian on Γ. This article shows the weighted weak type (1, 1) estimates and the weighted L^p norm inequalities for the spectral multipliers of L. We also obtain the weighted L^p norm inequalities for the commutators of the spectral multipliers of L with BMO functions which are new even for the unweighted case.     

A Remark on the Boundedness of Calderón–Zygmund Operators in Nony–homogeneous Spaces

Let μ be a Radon measure on Rd which may be non–doubling. The only condition satisfied by μ is that μ(B(x, r)) ≤ Cr ⁿ for all x ∈ ? ^d , r > 0 and some fixed 0 < n ≤ d. In this paper, the authors prove that the boundedness from H ¹(μ) into L ¹,^∞(μ) of a singular integral operator T with Calderón–Zygmund kernel of Hörmander type implies its L ²(μ)–boundedness.     

BMO and exponential Orlicz space estimates of the discrepancy function in arbitrary dimension

In the current paper, we obtain discrepancy estimates in exponential Orlicz and BMO spaces in arbitrary dimension d ≥ 3. In particular, we use dyadic harmonic analysis to prove that the dyadic product BMO and exp(L^2/(d?1)) norms of the discrepancy function of so-called digital nets of order two are bounded above by (logN)^(d?1)/2. The latter bound has been recently conjectured in several papers and is consistent with the best known low-discrepancy constructions. Such estimates play an important role as an intermediate step between the well-understood L_p bounds and the notorious open problem of finding the precise L_∞ asymptotics of the discrepancy function in higher dimensions, which is still elusive.     

Triebel-Lizorkin space boundedness of rough singular integrals associated to surfaces of revolution

We consider the boundedness of the rough singular integral operator T_(?,ψ,h) along a surface of revolution on the Triebel-Lizorkin space F~α_( p,q)(R~n) for ? ∈ H~1(~(Sn-1)) and ? ∈ Llog~+L(S~(n-1)) ∪_1q∞(B~((0,0))_q(S~(n-1))), respectively.     

On the geometric mean operator with variable limits of integration

A new criterion for the weighted L _p ?L _q boundedness of the Hardy operator with two variable limits of integration is obtained for 0 < q < q + 1 ≤ p < ∞. This criterion is applied to the characterization of the weighted L _p ?L _q boundedness of the corresponding geometric mean operator for 0 < q < p < ∞.     

Mikhlin’s problem on Carnot groups

We consider one class of singular integral operators over the functions on domains of Carnot groups. We prove the L _p boundedness, 1 < p > ∞, for the operators of this class. Similar operators over the functions on domains of Euclidean space were considered by Mikhlin.     

Boundedness of Hausdorff operators on Lebesgue spaces and Hardy spaces

In this paper, we study the boundedness of the Hausdorff operator H_? on the real line R. First, we start with an easy case by establishing the boundedness of the Hausdorff operator on the Lebesgue space L~p(R)and the Hardy space H~1(R). The key idea is to reformulate H_? as a Calder′on-Zygmund convolution operator,from which its boundedness is proved by verifying the Hrmander condition of the convolution kernel. Secondly,to prove the boundedness on the Hardy space H~p(R) with 0 p 1, we rewrite the Hausdorff operator as a singular integral operator with the non-convolution kernel. This novel reformulation, in combination with the Taibleson-Weiss molecular characterization of H~p(R) spaces, enables us to obtain the desired results. Those results significantly extend the known boundedness of the Hausdorff operator on H~1(R).     

Singular convolution integrals with operator-valued kernel

We study operators \(f\mapsto Kf\) of the form \((Kf)(t)=\int_{{\bf R}^{n}} k(t-s)f(s) {\rm d}s\), where f is a vector-valued function and k an operator-valued singular kernel. Sufficient conditions for boundedness on L ^p -spaces of UMD-valued functions are given in terms of a Hörmander-type condition involving R-boundedness. The results cover large classes of kernels and also provide new proofs of recent operator-valued Fourier multiplier theorems. Moreover, they give new information about families of singular integral operators.     

A Note on Campanato Spaces and Their Applications

In this paper, we obtain a version of the John–Nirenberg inequality suitable for Campanato spaces C_p,β with 0 < p < 1 and show that the spaces C_p,β are independent of the scale p ∈ (0,∞) in sense of norm when 0 < β < 1. As an application, we characterize these spaces by the boundedness of the commutators [b,B _α ] _j (j = 1, 2) generated by bilinear fractional integral operators B _α and the symbol b acting from L_p1 × L_p2 to L ^q for p1, p2 ∈ (1,∞), q ∈ (0,∞) and 1/q = 1/p1 + 1/p2 ? (α + β)/n.     

Characterizations for the fractional integral operators in generalized Morrey spaces on Carnot groups

In this paper, we study the boundedness of the fractional integral operator I _α on Carnot group G in the generalized Morrey spaces M _{p, φ} (G). We shall give a characterization for the strong and weak type boundedness of I _α on the generalized Morrey spaces, respectively. As applications of the properties of the fundamental solution of sub-Laplacian L on G, we prove two Sobolev–Stein embedding theorems on generalized Morrey spaces in the Carnot group setting.     

Multilinear dyadic operators and their commutators

We obtain a generalized paraproduct decomposition of the pointwise product of two or more functions that naturally gives rise to multilinear dyadic paraproducts and Haar multipliers. We then study the boundedness properties of these multilinear operators and their commutators with dyadic BMO functions. We also characterize the dyadic BMO functions via the boundedness of (a) certain paraproducts, and (b) the commutators of multilinear Haar multipliers and paraproduct operators.     

Bloom’s inequality: commutators in a two-weight setting

In 1985, Bloom characterized the boundedness of the commutator [b, H] as a map between a pair of weighted L^p spaces, where both weights are in A_p. The characterization is in terms of a novel BMO condition. We give a ‘modern’ proof of this result, in the case of p = 2. In a subsequent paper, this argument will be used to generalize Bloom’s result to all Calderón–Zygmund operators and dimensions.     

Sturm–Liouville problems in weighted spaces in domains with non-smooth edges. II

We consider a (generally, noncoercive) mixed boundary value problem in a bounded domain D of Rⁿ for a second order elliptic differential operator A(x, ?). The differential operator is assumed to be of divergent form in D and the boundary operator B(x, ?) is of Robin type on ?D. The boundary of D is assumed to be a Lipschitz surface. Besides, we distinguish a closed subset Y ? ?D and control the growth of solutions near Y. We prove that the pair (A, B) induces a Fredholm operator L in suitable weighted spaces of Sobolev type, the weight function being a power of the distance to the singular set Y. Moreover, we prove the completeness of root functions related to L.     

Boundedness for Higher Order Commutators of Fractional Integrals on Variable Exponent Herz–Morrey Spaces

In this paper, the boundedness for higher order commutators of fractional integrals is obtained on variable exponent Herz–Morrey spaces \( M\dot{K}_{p, q(\cdot )}^{\alpha (\cdot ), \lambda }(\mathbb {R}^{n})\) applying some properties of variable exponent and \(\mathrm {BMO}\) function, where \(\alpha (x)\in L^{\infty }(\mathbb {R}^{n})\) are log-Hölder continuous both at the origin and at infinity, and q(x) satisfies the logarithmic continuity condition.