Symbols of truncated Toeplitz operators

We consider three topics connected with coinvariant subspaces of the backward shift operator in Hardy spaces Hp:

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properties of truncated Toeplitz operators;

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Carleson-type embedding theorems for the coinvariant subspaces;

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factorizations of pseudocontinuable functions from H¹.

These problems turn out to be closely connected and even, in a sense, equivalent. The new approach based on the factorizations allows us to answer a number of challenging questions about truncated Toeplitz operators posed by D. Sarason.     

Schwarzian derivative and general Besov-type domains

We study univalent functions f for which belongs to a class of general Besov-type spaces. We give a characterization of the general Besov-type domains in terms of Carleson measure conditions on the Schwarzian derivative Sf, and mention some further connection to Teichmüller theory.     

Weighted Inequalities for the Generalized Maximal Operator in Martingale Spaces

The generalized maximal operator M in martingale spaces is considered. For 1 < p ≤ q < ∞, the authors give a necessary and sufficient condition on the pair ([^(m)]\hat \mu , v) for M to be a bounded operator from martingale space L ^p (v) into L ^q ([^(m)]\hat \mu ) or weak-L ^q ([^(m)]\hat \mu ), where [^(m)]\hat \mu is a measure on Ω × ℕ and v a weight on Ω. Moreover, the similar inequalities for usual maximal operator are discussed.     

Spherical Maximal Operators on Radial Functions

Let A_tf(x) denote the mean of f over a sphere of radius t and center x. We prove sharp estimates for the maximal function M_E f(X) = sup_t∈_E |Atf(x)| where E is a fixed set in IR⁺ and f is a radial function ∈ L^p(IR^d). Let P_d = d/(d?1) (the critical exponent for Stein's maximal function). For the cases (i) p < p_d, d ? 2, and (ii) p = p_d, d ? 3, and for p ? q ? ∞ we prove necessary and sufficient conditions on E for M_E to map radial functions in L^p to the Lorentz space L^P,q.     

Composition operators on weighted Dirichlet spaces

We characterize bounded and compact composition operators on weighted Dirichlet spaces. The method involves integral averages of the determining function for the operator, and the connection between composition operators on Dirichlet spaces and Toeplitz operators on Bergman spaces. We also present several examples and counter-examples that point out the borderlines of the result and its connections to other themes.

     

齐型空间上的Morrey空间极大算子有界性

本文研究齐型空间上Morrey空间的极大算子的有界性,得到的结果是已知 结果的本质改进和推广.     

A New Estimate for the Vector Valued Corona Problem

We improve an estimate of Fuhrmann and Vasyunin in the vector valued corona theorem.     

Area operators from H~p spaces to L~q spaces

We characterize non-negative measures μ on the unit disk D for which the area operator A μ is bounded or compact from Hardy space H p to L q (D) spaces.     

Bloch空间上紧的乘积算子

本文研究了Bloch函数空间上紧乘积算子，引入了消失α-Caleson测度，利用它给出Bloch空间和小Bloch空间上的乘积算子Mφf=φf紧性的一个充分条件。