Composition operators on the Lipschitz space in polydiscs

Let Un be the unit polydisc of Cn and φ= (φ1,...,φn? a holomorphic self-map of Un. Let 0≤α< 1. This paper shows that the composition operator Cφ, is bounded on the Lipschitz space Lipa(Un) if and only if there exists M > 0 such thatfor z∈Un. Moreover Cφ is compact on Lipa(Un) if and only if Cφ is bounded on Lipa(Un) and for every ε > 0, there exists a δ > 0 such that whenever dist(φ(z),σUn) <δ     

Carleson measures and the generalized Campanato spaces of vector-valued martingales

In this paper, the so-called(p, φ)-Carleson measure is introduced and the relationship between vector-valued martingales in the general Campanato spaces Lp,φ(X) and the(p, φ)-Carleson measures is investigated. Specifically, it is proved that for q ∈ [2, ∞), the measure dμ := ||dfk||~qdP ? dm is a(q, φ)-Carleson measure on ? × N for every f ∈ L_q,φ(X)if and only if X has an equivalent norm which is q-uniformly convex; while for p ∈(1, 2], the measure dμ :=||dfk||~pdP ? dm is a(p, φ)-Carleson measure on ? × N implies that f ∈ L_p,φ(X)if and only if X admits an equivalent norm which is p-uniformly smooth. This result extends an earlier result in the literature from BMO spaces to general Campanato spaces.     

COMPACT COMPOSITION OPERATORS ON WEIGHTED BERGMAN SPACES ON BOUNDED SYMMETRIC DOMAINS

In this article, we borrow the idea of using Schur’s test to characterize the compactness of composition operators on the weighted Bergman spaces in a bounded symmetric domain Ω, and verify that Cφ is compact on L q a (Ω, dv β ) if and only if K ( φ ( z ) ,φ ( z )) K ( z,z ) → 0 as z →φΩ under a mild condition, where K(z, w) is the Bergman kernel.     

Commuting dual Toeplitz operators on the harmonic Dirichlet space

In this paper,we characterize the symbols for(semi-)commuting dual Toeplitz operators on the orthogonal complement of the harmonic Dirichlet space.We show that for φ,ψ∈W~(1,∞),S_φS_ψ=S_ψ Sφ on(D_h)~⊥ if and only if φ and ψ satisfy one of the following conditions:(1) Both φ and ψ are harmonic functions;(2) There exist complex constants α and β,not both 0,such that φ=αψ +β.     

GABOR ANALYSIS OF THE SPACES M（p,q,w）（R~d） AND S（p,q,r,w,ω）（R~d）

Let g be a non-zero rapidly decreasing function and w be a weight function. In this article in analog to modulation space, we define the space M(p, q, w)(Rd) to be the subspace of tempered distributions f ∈ S′(Rd) such that the Gabor transform Vg(f) of f is in the weighted Lorentz space L(p, q, wdμ) (R2d). We endow this space with a suitable norm and show that it becomes a Banach space and invariant under time frequence shifts for 1 ≤ p, q ≤∞. We also investigate the embeddings between these spaces and the dual space of M(p, q, w)(Rd). Later we define the space S(p, q, r, w, ω)(Rd) for 1 < p < ∞, 1 ≤ q ≤∞. We endow it with a sum norm and show that it becomes a Banach convolution algebra. We also discuss some properties of S(p, q, r, w, ω)(Rd). At the end of this article, we characterize the multipliers of the spaces M(p, q, w)(Rd) and S(p, q, r, w, ω)(Rd).     

ENDPOINT ESTIMATES FOR THE COMMUTATOR OF PSEUDO-DIFFERENTIAL OPERATORS

It is well known that the commutator Tb of the Calder′on-Zygmund singular integral operator is bounded on Lp(Rn) for 1 p +∞if and only if b∈BMO [1]. On the other hand, the commutator Tb is bounded from H1(Rn) into L1(Rn) only if the function b is a constant [2]. In this article, we will discuss the boundedness of commutator of certain pseudo-differential operators on Hardy spaces H1. Let Tσbe the operators that its symbol is S01,δwith 0≤δ 1, if b∈LMO∞, then, the commutator [b, Tσ] is bounded from H1(Rn) into L1(Rn) and from L∞(Rn) into BMO(Rn); If [b, Tσ] is bounded from H1(Rn) into L1(Rn) or L∞(Rn) into BMO(Rn), then, b∈LMO_(loc).     

COMPOSITION OPERATORS ON THE LITTLE BLOCH SPACE IN POLYDISCS

Let Un be the unit polydisc of Cn and φ = (φ1,…,φn) a holomorphic self map of Un. This paper shows that the composition operator Cφ induced by φ is bounded on the little Bloch space β0*(Un) if and only if φ∈β0*(Un) for every l=1,2,…,n, and also gives a sufficient and necessary condition for the composition operator Cφ to be compact on the little Bloch spaceβ0* (Un).     

Jackson’s theorem in Q_p spaces

A Jackson type inequality in Q p spaces is established, i.e., for any f (z) = Σ∞ j=0 ajzj ∈ Qp , 0≤p ∞, a 1, and k-1 ∈ N,where ω(1/k, f, Q p ) is the modulus of continuity in Q p spaces and C(a) is an absolute constant depending only on the parameter a.     

Atomic decomposition and boundedness criterion of operators on multi-parameter hardy spaces of homogeneous type

The main purpose of this paper is to derive a new ( p, q)-atomic decomposition on the multi-parameter Hardy space Hp (X1 × X2 ) for 0 p0 p ≤ 1 for some p0 and all 1 q ∞, where X1 × X2 is the product of two spaces of homogeneous type in the sense of Coifman and Weiss. This decomposition converges in both Lq (X1 × X2 ) (for 1 q ∞) and Hardy space Hp (X1 × X2 ) (for 0 p ≤ 1). As an application, we prove that an operator T1, which is bounded on Lq (X1 × X2 ) for some 1 q ∞, is bounded from Hp (X1 × X2 ) to Lp (X1 × X2 ) if and only if T is bounded uniformly on all (p, q)-product atoms in Lp (X1 × X2 ). The similar boundedness criterion from Hp (X1 × X2 ) to Hp (X1 × X2 ) is also obtained.     

The Schwarz-Pick lemma for planar harmonic mappings

The classical Schwarz-Pick lemma for holomorphic mappings is generalized to planar harmonic mappings of the unit disk D completely. (I) For any 0 < r < 1 and 0 ρ < 1, the author constructs a closed convex domain Er,ρ such that F((z,r))  eiαEr,ρ = {eiαz : z ∈ Er,ρ} holds for every z ∈ D, w = ρeiα and harmonic mapping F with F(D)D and F(z) = w, where △(z,r) is the pseudo-disk of center z and pseudo-radius r; conversely, for every z ∈ D, w = ρeiα and w ∈ eiαEr,ρ, there exists a harmonic mapping F such that ...     

TWO-DIMENSIONAL MAXIMAL OPERATOR OF DYADIC DERIVATIVE ON VILENKIN MARTINGALE SPACES

In [1] the boundedness of one dimensional maximal operator of dyadic derivative is discussed.In this paper,we consider the two-dimensional maximal operator of dyadic derivative on Vilenkin martingale spaces.With the help of counter-example we prove that the maximal operator is not bounded from the Hardy space H q to the Hardy space H q for 0相似文献   

Cohn环与Grothendieck群

We introduce three classes of cohn rings C₁,C₂ and C₃). Let R and S are rings,φ : R→S is a ring homomorphism. We prove that R∈C_i if and only if R/J(R) ∈ C_i. In We also discuss the relation between the     

Characterizations and Extensions of Lipschitz-α Operators

In this work, we prove that a map F from a compact metric space K into a Banach space X over F is a Lipschitz-α operator if and only if for each σ in X^＊ the map σoF is a Lipschitz-α function on K. In the case that K = [a, b], we show that a map f from [a, b] into X is a Lipschitz-1 operator if and only if it is absolutely continuous and the map σ→ （σ o f）＇ is a bounded linear operator from X^＊ into L^∞（[a, b]）. When K is a compact subset of a finite interval （a, b） and 0 〈 α ≤ 1, we show that every Lipschitz-α operator f from K into X can be extended as a Lipschitz-α operator F from [a, b] into X with Lα（f） ≤ Lα（F） ≤ 3^1-α Lα（f）. A similar extension theorem for a little Lipschitz-α operator is also obtained.     

ON THE CONCAVE φ-INEQUALITIES FOR NONNEGATIVE SUBMARTINGALES

Let φ1, φ2 be nonnegative nondecreasing functions, and φl be concave. The authors prove the equivalence of the following two conditions:(i) Eφ1 (Mf) ≤ cEφ2(Zo+A∞) for every nonnegative submartingale f = (fn)n≥0 with it's Doob's Decomposition: f = Z + A, where Z is a martingale in L1 and A is a nonnegative incrasing and predictable process.(ii) There exists positive constants c, to such that ft∞φ1(s)/s2 ds ≤ c φ2(t)/t, t ＞ to.When φ1 = φ2 the condition (ii) above is equivalent to the classical condition -Pφ＜1. As a consequence, for a concave function φ, -Pφ＜ 1 if and only if Eφ1 (Mf) ≤ cEφ2 (Z0 + A∞)for every nonnegative submartingale f.     

BOUNDEDNESS OF COMPOSITION OPERATORS ON Dτ SPACES FOR τ>1

In this note, some conditions of composition operators on Dτspaces to be bounded are given by means of Carleson measures and pointwisemultipliers, for some ranges of τ. The authors prove that (i) Let 1<τ n+2 and 2k<τ 2k+1 (or 2k-1<τ 2k) for somepositive integer k. Suppose φ=(φ1,...,φn) be aunivalent mapping from B into itself, denote dμj(l)(z)=R(l)φj(z)2(k-l+2)(1-|z|2)2k-τ+1 dν(z) for l=1,2,...,k+1. If μj(l)φ-1 are (τ-2k+2l-4)-Carleson measures for all l, then the composition operator Cφon Dτis bounded; (ii) Let 1<τ n+2, φ=(φ1,...,φn)be univalent and the Fr echet derivativeof φ-1 be bounded onφ(B). If Rφj∈M(Dτ-2) forall j, then the composition operator Cφ on Dτis bounded; (iii) Let τ>n+2 and φ as in (ii).If φj∈Dτ for all j, then the compositionoperator Cφ on Dτ is bounded.     

M_φ-type Submodules over the Bidisk

Let H~2(D~2) be the Hardy space over the bidisk D~2,and let M_φ=[(z-φ(w))~2] be the submodule generated by(z-φ(w))~2,where φ(w) is a function in H∞(w).The related quotient module is denoted by N_φ=H~2(D~2)ΘM_φ.In the present paper,we study the Fredholmness of compression operators S_z,S_w on N_φ.When φ(w) is a nonconstant inner function,we prove that the Beurling type theorem holds for the fringe operator F_w on [(z-w)~2]Θ z[(z-w)~2] and the Beurling type theorem holds for the fringe operator Fz on M_φΘwM_φ if φ(0)=0.Lastly,we study some properties of F_w on[(z-w~2)~2]Θz[(z-w~2)~2].     

Hardy-type inequalities on strong and weak Orlicz-Lorentz spaces

In the present paper, the characterization of strong-type modular inequality ∫ 0 ∞φ(Sf (t))w(t)dt≤∫0∞ φ(Cf (t))w(t)dt, f↓ is given, where φ∈Δ’ and S is a Hardy operator. Furthermore, the equivalent conditions of modular inequalities and norm inequalities related to weak Orlicz-Lorentz spaces are researched. We also explore the conditions for Orlicz-Lorentz spaces and weak Orlicz-Lorentz spaces to be normable. Finally, the weak boundedness of certain Hardy-type operators on Orlicz-Lorentz spaces is studied.     

The Non-standard Characteristics of Comlete Uniform Space

In This paper,we prove that the uniform space(X,ψ）is complete if and only if for every remote point p in ^*X ,there exists a pseudo-metric d in the lattice set of ψ and a positive number r such that d(p,q)≥r for each q∈X.     

ON THE NEVANLINNA DIRECTION OF ALGEBROID FUNCTIONS

In this paper, we prove that for an algebroid function w(z), the singular direction arg z =φ0 , satisfying that for arbitrary ε(0 < ε < π 2 ) and any given a ∈ C, lim r → + ∞ n(r,φ0-ε,φ0 +ε,w=a)/ log r = +∞ holds with at most 2v possible exceptional values of a, is the Nevanlinna direction of w(z).