arXiv subjects

Dachun Yang

Publications and source records attributed to Dachun Yang.

At least 127 records · Page 7Linked to original sources

arXiv2020

Real-Variable Characterizations of Local Orlicz-Slice Hardy Spaces with Application to Bilinear Decompositions

Recently, both the bilinear decompositions $h^1(\mathbb{R}^n)\times \mathrm{\,bmo}(\mathbb{R}^n) \subset L^1 (\mathbb{R}^n)+h_\ast^Φ(\mathbb{R}^n)$ and $h^1(\mathbb{R}^n) \times \mathrm{bmo}(\mathbb{R}^n) \subset L^1 (\mathbb{R}^n) + h^{\log}(\mathbb{R}^n)$ were established. In this article, the authors prove in some sense that the former is sharp, while the latter is not. To this end, the authors first introduce the local Orlicz-slice Hardy space which contains the variant $h_\ast^Φ(\mathbb{R}^n)$ of the local Orlicz Hardy space introduced by A. Bonami and J. Feuto as a special case, and obtain its dual space by establishing its characterizations via atoms, finite atoms and various maximal functions, which are new even for $h_\ast^Φ(\mathbb R^n)$. The relationships $h_\ast^Φ(\mathbb{R}^n) \subsetneqq h^{\log}(\mathbb{R}^n)$ is also clarified.

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arXiv2020

Weighted Global Regularity Estimates for Elliptic Problems with Robin Boundary Conditions in Lipschitz Domains

Let $n\ge2$ and $Ω$ be a bounded Lipschitz domain in $\mathbb{R}^n$. In this article, the authors investigate global (weighted) estimates for the gradient of solutions to Robin boundary value problems of second order elliptic equations of divergence form with real-valued, bounded, measurable coefficients in $Ω$. More precisely, let $p\in(n/(n-1),\infty)$. Using a real-variable argument, the authors obtain two necessary and sufficient conditions for $W^{1,p}$ estimates of solutions to Robin boundary value problems, respectively, in terms of a weak reverse Hölder inequality with exponent $p$ or weighted $W^{1,q}$ estimates of solutions with $q\in(n/(n-1),p]$ and some Muckenhoupt weights. As applications, the authors establish some global regularity estimates for solutions to Robin boundary value problems of second order elliptic equations of divergence form with small $\mathrm{BMO}$ coefficients, respectively, on bounded Lipschitz domains, $C^1$ domains or (semi-)convex domains, in the scale of weighted Lebesgue spaces, via some quite subtle approach which is different from the existing ones and, even when $n=3$ in case of bounded $C^1$ domains, also gives an alternative correct proof of some know result. By this and some technique from harmonic analysis, the authors further obtain the global regularity estimates, respectively, in Morrey spaces, (Musielak--)Orlicz spaces and variable Lebesgue spaces

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arXiv2019

Littlewood-Paley Characterizations of Hardy-type Spaces Associated with Ball Quasi-Banach Function Spaces

Let $X$ be a ball quasi-Banach function space on ${\mathbb R}^n$. In this article, assuming that the powered Hardy--Littlewood maximal operator satisfies some Fefferman--Stein vector-valued maximal inequality on $X$ and is bounded on the associated space, the authors establish various Littlewood--Paley function characterizations of the Hardy space $H_X({\mathbb R}^n)$ associated with $X$, under some weak assumptions on the Littlewood--Paley functions. To this end, the authors also establish a useful estimate on the change of angles in tent spaces associated with $X$. All these results have wide applications. Particularly, when $X:=M_r^p({\mathbb R}^n)$ (the Morrey space), $X:=L^{\vec{p}}({\mathbb R}^n)$ (the mixed-norm Lebesgue space), $X:=L^{p(\cdot)}({\mathbb R}^n)$ (the variable Lebesgue space), $X:=L_ω^p({\mathbb R}^n)$ (the weighted Lebesgue space) and $X:=(E_Φ^r)_t({\mathbb R}^n)$ (the Orlicz-slice space), the Littlewood--Paley function characterizations of $H_X({\mathbb R}^n)$ obtained in this article improve the existing results via weakening the assumptions on the Littlewood--Paley functions and widening the range of $λ$ in the Littlewood--Paley $g_λ^*$-function characterization of $H_X(\mathbb R^n)$.

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arXiv2019

Applications of Hardy Spaces Associated with Ball Quasi-Banach Function Spaces

Let $X$ be a ball quasi-Banach function space satisfying some minor assumptions. In this article, the authors establish the characterizations of $H_X(\mathbb{R}^n)$, the Hardy space associated with $X$, via the Littlewood--Paley $g$-functions and $g_λ^\ast$-functions. Moreover, the authors obtain the boundedness of Calderón--Zygmund operators on $H_X(\mathbb{R}^n)$. For the local Hardy-type space $h_X(\mathbb{R}^n)$ associated with $X$, the authors also obtain the boundedness of $S^0_{1,0}(\mathbb{R}^n)$ pseudo-differential operators on $h_X(\mathbb{R}^n)$ via first establishing the atomic characterization of $h_X(\mathbb{R}^n)$. Furthermore, the characterizations of $h_X(\mathbb{R}^n)$ by means of local molecules and local Littlewood--Paley functions are also given. The results obtained in this article have a wide range of generality and can be applied to the classical Hardy space, the weighted Hardy space, the Herz--Hardy space, the Lorentz--Hardy space, the Morrey--Hardy space, the variable Hardy space, the Orlicz-slice Hardy space and their local versions. Some special cases of these applications are even new and, particularly, in the case of the variable Hardy space, the $g_λ^\ast$-function characterization obtained in this article improves the known results via widening the range of $λ$.

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arXiv2019

Real-Variable Characterizations of New Anisotropic Mixed-Norm Hardy Spaces

Let $\vec{p}\in(0,\infty)^n$ and $A$ be a general expansive matrix on $\mathbb{R}^n$. In this article, via the non-tangential grand maximal function, the authors first introduce the anisotropic mixed-norm Hardy spaces $H_A^{\vec{p}}(\mathbb{R}^n)$ associated with $A$ and then establish their radial or non-tangential maximal function characterizations. Moreover, the authors characterize $H_A^{\vec{p}}(\mathbb{R}^n)$, respectively, by means of atoms, finite atoms, Lusin area functions, Littlewood-Paley $g$-functions or $g_λ^\ast$-functions via first establishing an anisotropic Fefferman-Stein vector-valued inequality on the mixed-norm Lebesgue space $L^{\vec{p}}(\mathbb{R}^n)$. In addition, the authors also obtain the duality between $H_A^{\vec{p}}(\mathbb{R}^n)$ and the anisotropic mixed-norm Campanato spaces. As applications, the authors establish a criterion on the boundedness of sublinear operators from $H_A^{\vec{p}}(\mathbb{R}^n)$ into a quasi-Banach space. Applying this criterion, the authors then obtain the boundedness of anisotropic convolutional $δ$-type and non-convolutional $β$-order Calderón-Zygmund operators from $H_A^{\vec{p}}(\mathbb{R}^n)$ to itself [or to $L^{\vec{p}}(\mathbb{R}^n)$]. As a corollary, the boundedness of anisotropic convolutional $δ$-type Calderón-Zygmund operators on the mixed-norm Lebesgue space $L^{\vec{p}}(\mathbb{R}^n)$ with $\vec{p}\in(1,\infty)^n$ is also presented.

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arXiv2019

Quantitative Boundedness of Littlewood--Paley Functions on Weighted Lebesgue Spaces in the Schrödinger Setting

Let $L:=-Δ+V$ be the Schrödinger operator on $\mathbb{R}^n$ with $n\geq 3$, where $V$ is a non-negative potential which belongs to certain reverse Hölder class $RH_q(\mathbb{R}^n)$ with $q\in (n/2,\,\infty)$. In this article, the authors obtain the quantitative weighted boundedness of Littlewood--Paley functions $g_L$, $S_L$ and $g_{L,\,λ}^\ast$, associated to $L$, on weighted Lebesgue spaces $L^p(w)$, where $w$ belongs to the class of Muckenhoupt $A_p$ weights adapted to $L$.

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arXiv2019

Buerling-Ahlfors Commutators on Weighted Morrey Spaces and Applications to Beltrami Equations

Let $p\in(1, \infty)$, $κ\in(0, 1)$ and $w\in A_p(\mathbb C).$ In this article, the authors obtain a boundedness (resp., compactness) characterization of the Buerling-Ahlfors commutator $[\mathcal B, b]$ on the weighted Morrey space $L_w^{p,\,κ}(\mathbb C)$ via $\mathrm{BMO}(\mathbb C)$ [resp., $\mathrm{CMO}(\mathbb C)$], where $\mathcal B$ denotes the Buerling-Ahlfors transform and $b\in \mathrm{BMO}(\mathbb C)$ [resp., $\mathrm{CMO}(\mathbb C)$]. Moreover, an application to the Beltrami equation is also given.

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arXiv2019

On Function Spaces with Mixed Norms --- A Survey

The targets of this article are threefold. The first one is to give a survey on the recent developments of function spaces with mixed norms, including mixed Lebesgue spaces, iterated weak Lebesgue spaces, weak mixed-norm Lebesgue spaces and mixed Morrey spaces as well as anisotropic mixed-norm Hardy spaces. The second one is to provide a detailed proof for a useful inequality about mixed Lebesgue norms and the Hardy--Littlewood maximal operator and also to improve some known results on the maximal function characterizations of anisotropic mixed-norm Hardy spaces and the boundedness of Calderón--Zygmund operators from these anisotropic mixed-norm Hardy spaces to themselves or to mixed Lebesgue spaces. The last one is to correct some errors and seal some gaps existing in the known articles.

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arXiv2019

Real-Variable Characterizations of Local Hardy Spaces on Spaces of Homogeneous Type

Suppose that $(X,d,μ)$ is a space of homogeneous type, with upper dimension $μ$, in the sense of R. R. Coifman and G. Weiss. Let $η$ be the Hölder regularity index of wavelets constructed by P. Auscher and T. Hytönen. In this article, the authors introduce the local Hardy space $h^{*,p}(X)$ via local grand maximal functions and also characterize $h^{*,p}(X)$ via local radial maximal functions, local non-tangential maximal functions, locally atoms and local Littlewood--Paley functions. Furthermore, the authors establish the relationship between the global and the local Hardy spaces. Finally, the authors also obtain the finite atomic characterizations of $h^{*,p}(X)$. As an application, the authors give the dual spaces of $h^{*,p}(X)$ when $p\in(ω/(ω+η),1)$, which further completes the result of G. Dafni and H. Yue on the dual space of $h^{*,1}(X)$. This article also answers the question of R. R. Coifman and G. Weiss on the nonnecessity of any additional geometric assumptions except the doubling condition for the radial maximal function characterization of $H^1_{\mathrm{cw}}(X)$ when $μ(X)<\infty$.

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arXiv2019

The Haar System in Besov-type Spaces

Some Besov-type spaces $B^{s,τ}_{p,q}(\mathbb{R}^n)$ can be characterized in terms of the behavior of the Fourier--Haar coefficients. In this article, the authors discuss some necessary restrictions for the parameters $s$, $τ$, $p$, $q$ and $n$ of this characterization. Therefore, the authors measure the regularity of the characteristic function $\mathcal X$ of the unit cube in $\mathbb{R}^n$ via the Besov-type spaces $B^{s,τ}_{p,q}(\mathbb{R}^n)$. Furthermore, the authors study necessary and sufficient conditions such that the operation $\langle f, \mathcal{X} \rangle$ generates a continuous linear functional on $B^{s,τ}_{p,q}(\mathbb{R}^n)$.

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arXiv2019

Weak Hardy-Type Spaces Associated with Ball Quasi-Banach Function Spaces I: Decompositions with Applications to Boundedness of Calderón--Zygmund Operators

Let $X$ be a ball quasi-Banach function space on ${\mathbb R}^n$. In this article, the authors introduce the weak Hardy-type space $WH_X({\mathbb R}^n)$, associated with $X$, via the radial maximal function. Assuming that the powered Hardy--Littlewood maximal operator satisfies some Fefferman--Stein vector-valued maximal inequality on $X$ as well as it is bounded on both the weak ball quasi-Banach function space $WX$ and the associated space, the authors then establish several real-variable characterizations of $WH_X({\mathbb R}^n)$, respectively, in terms of various maximal functions, atoms and molecules. As an application, the authors obtain the boundedness of Calderón--Zygmund operators from the Hardy space $H_X({\mathbb R}^n)$ to $WH_X({\mathbb R}^n)$, which includes the critical case. All these results are of wide applications. Particularly, when $X:=M_q^p({\mathbb R}^n)$ (the Morrey space), $X:=L^{\vec{p}}({\mathbb R}^n)$ (the mixed-norm Lebesgue space) and $X:=(E_Φ^q)_t({\mathbb R}^n)$ (the Orlicz-slice space), which are all ball quasi-Banach function spaces but not quasi-Banach function spaces, all these results are even new. Due to the generality, more applications of these results are predictable.

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arXiv2019

Weak Hardy-Type Spaces Associated with Ball Quasi-Banach Function Spaces II: Littlewood--Paley Characterizations and Real Interpolation

Let $X$ be a ball quasi-Banach function space on ${\mathbb R}^n$. In this article, assuming that the powered Hardy--Littlewood maximal operator satisfies some Fefferman--Stein vector-valued maximal inequality on $X$ as well as it is bounded on both the weak ball quasi-Banach function space $WX$ and the associated space, the authors establish various Littlewood--Paley function characterizations of $WH_X({\mathbb R}^n)$ under some weak assumptions on the Littlewood--Paley functions. The authors also prove that the real interpolation intermediate space $(H_{X}({\mathbb R}^n),L^\infty({\mathbb R}^n))_{θ,\infty}$, between the Hardy space associated with $X$, $H_{X}({\mathbb R}^n)$, and the Lebesgue space $L^\infty({\mathbb R}^n)$, is $WH_{X^{{1}/{(1-θ)}}}({\mathbb R}^n)$, where $θ\in (0, 1)$. All these results are of wide applications. Particularly, when $X:=M_q^p({\mathbb R}^n)$ (the Morrey space), $X:=L^{\vec{p}}({\mathbb R}^n)$ (the mixed-norm Lebesgue space) and $X:=(E_Φ^q)_t({\mathbb R}^n)$ (the Orlicz-slice space), all these results are even new; when $X:=L_ω^Φ({\mathbb R}^n)$ (the weighted Orlicz space), the result on the real interpolation is new and, when $X:=L^{p(\cdot)}({\mathbb R}^n)$ (the variable Lebesgue space) and $X:=L_ω^Φ({\mathbb R}^n)$, the Littlewood--Paley function characterizations of $WH_X({\mathbb R}^n)$ obtained in this article improves the existing results via weakening the assumptions on the Littlewood--Paley functions.

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arXiv2019

Localized John--Nirenberg--Campanato Spaces

Let $p\in(1,\infty)$, $q\in[1,\infty)$, $s\in{\mathbb Z}_{+}$, $α\in[0,\infty)$ and $\mathcal{X}$ be $\mathbb R^n$ or a cube $Q_0\subsetneqq\mathbb R^n$. In this article, the authors first introduce the localized John--Nirenberg--Campanato space $jn_{(p,q,s)_α}(\mathcal{X})$ and show that the localized Campanato space is the limit case of $jn_{(p,q,s)_α}(\mathcal{X})$ as $p\to\infty$. By means of local atoms and the weak-$*$ topology, the authors then introduce the localized Hardy-kind space $hk_{(p',q',s)_α}(\mathcal{X})$ which proves the predual space of $jn_{(p,q,s)_α}(\mathcal{X})$. Moreover, the authors prove that $hk_{(p',q',s)_α}(\mathcal{X})$ is invariant when $1<q<p$, where $p'$ or $q'$ denotes the conjugate number of $p$ or $q$, respectively. All these results are new even for the localized John--Nirenberg space.

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arXiv2019

John--Nirenberg--Campanato Spaces

Let $p\in (1,\infty)$, $q\in[1,\infty)$, $α\in [0,\infty)$ and $s$ be a non-negative integer. In this article, the authors introduce the John--Nirenberg-Campanato space $JN_{(p,q,s)_α}(\mathcal{X})$, where $\mathcal{X}$ is ${\mathbb R}^n$ or any closed cube $Q_0\subsetneqq{\mathbb R}^n$, which when $α=0$ and $s=0$ coincides with the $JN_p$-space introduced by F. John and L. Nirenberg in the sense of equivalent norms. The authors then give the predual space of $JN_{(p,q,s)_α}(\mathcal{X})$ and a John-Nirenberg type inequality of John--Nirenberg-Campanato spaces. Moreover, the authors prove that the classical Campanato space serves as a limit space of $JN_{(p,q,s)_α}(\mathcal{X})$ when $p\to \infty$.

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arXiv2018

Atomic Characterizations of Weak Martingale Musielak--Orlicz Hardy Spaces and Their Applications

Let $(Ω,\mathcal{F},\mathbb{P})$ be a probability space and $φ:\ Ω\times[0,\infty)\to [0,\infty)$ be a Musielak--Orlicz function. In this article, the authors establish the atomic characterizations of weak martingale Musielak--Orlicz Hardy spaces $WH_φ^s(Ω)$, $WH_φ^M(Ω)$, $WH_φ^S(Ω)$, $WP_φ(Ω)$ and $WQ_φ(Ω)$. Using these atomic characterizations, the authors then obtain the boundedness of sublinear operators from weak martingale Musielak--Orlicz Hardy spaces to weak Musielak--Orlicz spaces, and some martingale inequalities which further clarify the relationships among $WH_φ^s(Ω)$, $WH_φ^M(Ω)$, $WH_φ^S(Ω)$, $WP_φ(Ω)$ and $WQ_φ(Ω)$. All these results improve and generalize the corresponding results on weak martingale Orlicz--Hardy spaces. Moreover, the authors also improve all the known results on weak martingale Musielak--Orlicz Hardy spaces. In particular, both the boundedness of sublinear operators and the martingale inequalities, for the weak weighted martingale Hardy spaces as well as for the weak weighted martingale Orlicz--Hardy spaces, are new.

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arXiv2018

New Martingale Inequalities and Applications to Fourier Analysis

Let $(Ω,\mathcal{F},\mathbb{P})$ be a probability space and $φ:\ Ω\times[0,\infty)\to[0,\infty)$ be a Musielak-Orlicz function. In this article, the authors prove that the Doob maximal operator is bounded on the Musielak-Orlicz space $L^φ(Ω)$. Using this and extrapolation method, the authors then establish a Fefferman-Stein vector-valued Doob maximal inequality on $L^φ(Ω)$. As applications, the authors obtain the dual version of the Doob maximal inequality and the Stein inequality for $L^φ(Ω)$, which are new even in weighted Orlicz spaces. The authors then establish the atomic characterizations of martingale Musielak-Orlicz Hardy spaces $H_φ^s(Ω)$, $P_φ(Ω)$, $Q_φ(Ω)$, $H_φ^S(Ω)$ and $H_φ^M(Ω)$. From these atomic characterizations, the authors further deduce some martingale inequalities between different martingale Musielak-Orlicz Hardy spaces, which essentially improve the corresponding results in Orlicz space case and are also new even in weighted Orlicz spaces. By establishing the Davis decomposition on $H_φ^S(Ω)$ and $H_φ^M(Ω)$, the authors obtain the Burkholder-Davis-Gundy inequality associated with Musielak--Orlicz functions. Finally, using the previous martingale inequalities, the authors prove that the maximal Fejér operator is bounded from $H_φ[0,1)$ to $L^φ[0,1)$, which further implies some convergence results of the Fejér means; these results are new even for the weighted Hardy spaces.

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arXiv2018

New Characterizations of Musielak-Orlicz-Sobolev Spaces via Sharp Ball Averaging Functions

In this article, the authors establish a new characterization of the Musielak--Orlicz--Sobolev space on $\mathbb{R}^n$, which includes the classical Orlicz--Sobolev space, the weighted Sobolev space and the variable exponent Sobolev space as special cases, in terms of sharp ball averaging functions. Even in a special case, namely, the variable exponent Sobolev space, the obtained result in this article improves the corresponding result obtained by P. Hästö and A. M. Ribeiro [Commun. Contemp. Math. 19 (2017), 1650022, 13 pp] via weakening the assumption $f\in L^1(\mathbb R^n)$ into $f\in L_{\mathrm{loc}}^1(\mathbb R^n)$, which was conjectured to be true by Hästö and Ribeiro in the aforementioned same article.

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arXiv2018

Atomic and Maximal Function Characterizations of Musielak-Orlicz-Hardy Spaces Associated to Non-negative Self-adjoint Operators on Spaces of Homogeneous Type

Let $\mathcal{X}$ be a metric space with doubling measure and $L$ a non-negative self-adjoint operator on $L^2(\mathcal{X})$ whose heat kernels satisfy the Gaussian upper bound estimates. Assume that the growth function $φ:\ \mathcal{X}\times[0,\infty) \to[0,\infty)$ satisfies that $φ(x,\cdot)$ is an Orlicz function and $φ(\cdot,t)\in {\mathbb A}_{\infty}(\mathcal{X})$ (the class of uniformly Muckenhoupt weights). Let $H_{φ,\,L}(\mathcal{X})$ be the Musielak-Orlicz-Hardy space defined via the Lusin area function associated with the heat semigroup of $L$. In this article, the authors characterize the space $H_{φ,\,L}(\mathcal{X})$ by means of atoms, non-tangential and radial maximal functions associated with $L$. In particular, when $μ(\mathcal{X})<\infty$, the local non-tangential and radial maximal function characterizations of $H_{φ,\,L}(\mathcal{X})$ are obtained. As applications, the authors obtain various maximal function and the atomic characterizations of the "geometric" Musielak-Orlicz-Hardy spaces $H_{φ,\,r}(Ω)$ and $H_{φ,\,z}(Ω)$ on the strongly Lipschitz domain $Ω$ in $\mathbb{R}^n$ associated with second-order self-adjoint elliptic operators with the Dirichlet and the Neumann boundary conditions; even when $φ(x,t):=t$ for any $x\in\mathbb{R}^n$ and $t\in[0,\infty)$, the equivalent characterizations of $H_{φ,\,z}(Ω)$ given in this article improve the known results via removing the assumption that $Ω$ is unbounded.

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