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Dongyong Yang

Publications and source records attributed to Dongyong Yang.

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A Moser type inequality for Bessel Laplace equations and applications

In this paper, we study Bessel operators and Bessel Laplace equations studied by Weinstein, Huber, and related the harmonic function theory introduced by Muckenhoupt--Stein. We establish the Moser type inequality for these harmonic functions, which is missing in this setting before. We then apply it to give a direct proof for the equivalence of characterizations of the Hardy spaces associated to Bessel operator via non-tangential maximal function and radial maximal function defined in terms of the Poisson semigroup.

math.AP↗

Characterizations of product Hardy spaces in Bessel setting

In this paper, we work in the setting of Bessel operators and Bessel Laplace equations studied by Weinstein, Huber, and the harmonic function theory in this setting introduced by Muckenhoupt--Stein, especially the generalised Cauchy--Riemann equations and the conjugate harmonic functions. We provide the equivalent characterizations of product Hardy spaces associated with Bessel operators in terms of the Bessel Riesz transforms, non-tangential and radial maximal functions defined via Poisson and heat semigroups, based on the atomic decomposition, the extension of Merryfield's result which connects the product non-tangential maximal function and area function, and on the grand maximal function technique which connects the product non-tangential and radial maximal function. We then obtain directly the decomposition of the product BMO space associated with Bessel operators. These results are a first extension for product Hardy and BMO associated to a differential operator other than the Laplacian and are a major step beyond the Chang--Fefferman setting.

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Oscillation and variation for Riesz transform associated with Bessel operators

Let $λ>0$ and $\triangle_λ:=-\frac{d^2}{dx^2}-\frac{2λ}{x} \frac d{dx}$ be the Bessel operator on $\mathbb R_+:=(0,\infty)$. We show that the oscillation operator $\mathcal{O}(R_{Δ_λ,\ast})$ and variation operator $\mathcal{V}_ρ(R_{Δ_λ,\ast})$ of the Riesz transform $R_{Δ_λ}$ associated with $Δ_λ$ are both bounded on $L^p(\mathbb R_+, dm_λ)$ for $p\in(1,\,\infty)$, from $L^1(\mathbb{R}_{+},dm_λ)$ to $L^{1,\,\infty}(\mathbb{R}_{+},dm_λ)$, and from $L^{\infty}(\mathbb{R}_{+},dm_λ)$ to $BMO(\mathbb{R}_{+},dm_λ)$, where $ρ\in (2,\infty)$ and $dm_λ(x):=x^{2λ}dx$. As an application, we give the corresponding $L^p$-estimates for $β$-jump operators and the number of up-crossing.

math.AP↗

Oscillation and variation for semigroups associated with Bessel operators

Let $λ>0$ and $\triangle_λ:=-\frac{d^2}{dx^2}-\frac{2λ}{x} \frac d{dx}$ be the Bessel operator on $\mathbb R_+:=(0,\infty)$. We show that the oscillation operator ${\mathcal O(P^{[λ]}_\ast)}$ and variation operator ${\mathcal V}_ρ(P^{[λ]}_\ast)$ of the Poisson semigroup $\{P^{[λ]}_t\}_{t>0}$ associated with $Δ_λ$ are both bounded on $L^p(\mathbb R_+, dm_λ)$ for $p\in(1, \infty)$, $BMO({{\mathbb R}_+},dm_λ)$, from $L^1({{\mathbb R}_+},dm_λ)$ to $L^{1,\,\infty}({{\mathbb R}_+},dm_λ)$, and from $H^1({{\mathbb R}_+},dm_λ)$ to $L^1({{\mathbb R}_+},dm_λ)$, where $ρ\in(2, \infty)$ and $dm_λ(x):=x^{2λ}\,dx$. As an application, an equivalent characterization of $H^1({{\mathbb R}_+},dm_λ)$ in terms of ${\mathcal V}_ρ(P^{[λ]}_\ast)$ is also established. All these results hold if $\{P^{[λ]}_t\}_{t>0}$ is replaced by the heat semigroup $\{W^{[λ]}_t\}_{t>0}$. }

math.AP↗

Compactness of Riesz transform commutator associated with Bessel operators

Let $λ>0$ and $\triangle_λ:=-\frac{d^2}{dx^2}-\frac{2λ}{x} \frac d{dx}$ be the Bessel operator on $\mathbb R_+:=(0,\infty)$. We first introduce and obtain an equivalent characterization of ${\rm CMO}(\mathbb R_+,\, x^{2λ}dx)$. By this equivalent characterization and establishing a new version of the Fréchet-Kolmogorov theorem in the Bessel setting, we further prove that a function $b\in {\rm BMO}(\mathbb R_+,\, x^{2λ}dx)$ is in ${\rm CMO}(\mathbb R_+,\, x^{2λ}dx)$ if and only if the Riesz transform commutator $[b, R_{Δ_λ}]$ is compact on $L^p(\mathbb R_+, x^{2λ}dx)$ for any $p\in(1, \infty)$.

math.CA↗

Factorization for Hardy spaces and characterization for BMO spaces via commutators in the Bessel setting

Fix $λ>0$. Consider the Hardy space $H^1(\mathbb{R}_+,dm_λ)$ in the sense of Coifman and Weiss, where $\mathbb{R_+}:=(0,\infty)$ and $dm_λ:=x^{2λ}dx$ with $dx$ the Lebesgue measure. Also consider the Bessel operators $Δ_λ:=-\frac{d^2}{dx^2}-\frac{2λ}{x} \frac d{dx}$, and $S_λ:=-\frac{d^2}{dx^2}+\frac{λ^2-λ}{x^2}$ on $\mathbb{R_+}$. The Hardy spaces $H^1_{Δ_λ}$ and $H^1_{S_λ}$ associated with $Δ_λ$ and $S_λ$ are defined via the Riesz transforms $R_{Δ_λ}:=\partial_x (Δ_λ)^{-1/2}$ and $R_{S_λ}:= x^λ\partial_x x^{-λ} (S_λ)^{-1/2}$, respectively. It is known that $H^1_{Δ_λ}$ and $H^1(\mathbb{R}_+,dm_λ)$ coincide but they are different from $H^1_{S_λ}$. In this article, we prove the following: (a) a weak factorization of $H^1(\mathbb{R}_+,dm_λ)$ by using a bilinear form of the Riesz transform $R_{Δ_λ}$, which implies the characterization of the BMO space associated to $Δ_λ$ via the commutators related to $R_{Δ_λ}$; (b) the BMO space associated to $S_λ$ can not be characterized by commutators related to $R_{S_λ}$, which implies that $H^1_{S_λ}$ does not have a weak factorization via a bilinear form of the Riesz transform $R_{S_λ}$.

math.CA↗

Hardy spaces $H^p$ over non-homogeneous metric measure spaces and their applications

Let $({\mathcal X},d,μ)$ be a metric measure space satisfying both the geometrically doubling and the upper doubling conditions. Let $ρ\in (1,\infty)$, $0<p\le1\le q\le\infty$, $p\neq q$, $γ\in[1,\infty)$ and $ε\in(0,\infty)$. In this article, the authors introduce the atomic Hardy space ${\widetilde H_{\mathrm{atb},\,ρ}^{p,\,q,\,γ}(μ)}$ and the molecular Hardy space ${\widetilde H_{\rm{mb},\,ρ}^{p,\,q,\,γ,\,ε}(μ)}$ via the discrete coefficient $\widetilde{K}^{(ρ),\,p}_{B,\,S}$, and prove that the Calderón-Zygmund operator is bounded from ${\widetilde H_{\rm{mb},\,ρ}^{p,\,q,\,γ,\,δ}(μ)}$ (or ${\widetilde H_{\rm{atb},\,ρ}^{p,\,q,\,γ}(μ)}$) into $L^p(μ)$, and from ${\widetilde H_{\rm{atb},\,ρ(ρ+1)}^{p,\,q,\,γ+1}(μ)}$ into ${\widetilde H_{\rm{mb},\,ρ}^{p,\,q,\,γ,\,\frac12(δ-\fracν{p}+ν)}(μ)}$ whose genealized fractional versions are also obtained. The authors also introduce the $ρ$-weakly doubling condition, with $ρ\in (1,\infty)$, of the measure $μ$ and construct a non-doubling measure $μ$ satisfying this condition. If $μ$ is $ρ$-weakly doubling, the authors further introduce the Campanato space ${\mathcal E}^{α,\,q}_{ρ,\,η,\,γ}(μ)$ and show that ${\mathcal E}^{α,\,q}_{ρ,\,η,\,γ}(μ)$ is independent of the choices of $ρ$, $η$, $γ$ and $q$; the authors then introduce the atomic Hardy space $\widehat H_{\rm{atb},\,ρ}^{p,\,q,\,γ}(μ)$ and the molecular Hardy space $\widehat H_{\rm{mb},\,ρ}^{p,\,q,\,γ,\,ε}(μ)$, which coincide with each other; the authors finally prove that $\widehat{H}_{\rm{atb},\,ρ}^{p,\,q,\,γ}(μ)$ is the predual of ${\mathcal E}^{1/p-1,\,1}_{ρ,\,ρ,\,1}(μ)$. Moreover, relations of these Hardy spaces are also discussed.

math.CA↗

The Hardy Space $H^1$ on Non-homogeneous Metric Spaces

Let $({\mathcal X}, d, μ)$ be a metric measure space and satisfy the so-called upper doubling condition and the geometrical doubling condition. In this paper, we introduce the atomic Hardy space $H^1(μ)$ and prove that its dual space is the known space ${\rm RBMO}(μ)$ in this context. Using this duality, we establish a criterion for the boundedness of linear operators from $H^1(μ)$ to any Banach space. As an application of this criterion, we obtain the boundedness of Calderón--Zygmund operators from $H^1(μ)$ to $L^1(μ)$.

math.CA↗

An Interpolation Theorem for Sublinear Operators on Non-homogeneous Metric Measure Spaces

Let $({\mathcal X}, d, μ)$ be a metric measure space and satisfy the so-called upper doubling condition and the geometrically doubling condition. In this paper, the authors establish an interpolation result that a sublinear operator which is bounded from the Hardy space $H^1(μ)$ to $L^{1,\,\infty}(μ)$ and from $L^\infty(μ)$ to the BMO-type space ${\mathop\mathrm{RBMO}}(μ)$ is also bounded on $L^p(μ)$ for all $p\in(1,\,\infty)$. This extension is not completely straightforward and improves the existing result.

math.AP↗

Real-Variable Characterizations Of Hardy Spaces Associated With Bessel Operators

Let $λ>0$, $p\in((2\lz+1)/(2\lz+2), 1]$, and $\triangle_λ\equiv-\frac{d^2}{dx^2}-\frac{2λ}{x} \frac d{dx}$ be the Bessel operator. In this paper, the authors establish the characterizations of atomic Hardy spaces $H^p((0, \infty), dm_λ)$ associated with $\triangle_λ$ in terms of the radial maximal function, the nontangential maximal function, the grand maximal function, the Littlewood-Paley $g$-function and the Lusin-area function, where $dm_λ(x)\equiv x^{2λ}\,dx$. As an application, the authors further obtain the Riesz transform characterization of these Hardy spaces.

math.CA↗

Boundedness of Calderón-Zygmund Operators on Non-homogeneous Metric Measure Spaces

Let $({\mathcal X}, d, μ)$ be a separable metric measure space satisfying the known upper doubling condition, the geometrical doubling condition and the non-atomic condition that $μ(\{x\})=0$ for all $x\in{\mathcal X}$. In this paper, we show that the boundedness of a Calderón-Zygmund operator $T$ on $L^2(μ)$ is equivalent to that of $T$ on $L^p(μ)$ for some $p\in (1, \infty)$, and that of $T$ from $L^1(μ)$ to $L^{1,\,\infty}(μ).$ As an application, we prove that if $T$ is a Calderón-Zygmund operator bounded on $L^2(μ)$, then its maximal operator is bounded on $L^p(μ)$ for all $p\in (1, \infty)$ and from the space of all complex-valued Borel measures on ${\mathcal X}$ to $L^{1,\,\infty}(μ)$. All these results generalize the corresponding results of Nazarov et al. on metric spaces with measures satisfying the so-called polynomial growth condition.

math.CA↗

Localized BMO and BLO Spaces on RD-Spaces and Applications to Schrödinger Operators

An RD-space ${\mathcal X}$ is a space of homogeneous type in the sense of Coifman and Weiss with the additional property that a reverse doubling condition holds in ${\mathcal X}$. Let $ρ$ be an admissible function on RD-space ${\mathcal X}$. The authors first introduce the localized spaces $\mathrm{BMO}_ρ({\mathcal X})$ and $\mathrm{BLO}_ρ({\mathcal X})$ and establish their basic properties, including the John-Nirenberg inequality for $\mathrm{BMO}_ρ({\mathcal X})$, several equivalent characterizations for $\mathrm{BLO}_ρ({\mathcal X})$, and some relations between these spaces. Then the authors obtain the boundedness on these localized spaces of several operators including the natural maximal operator, the Hardy-Littlewood maximal operator, the radial maximal functions and their localized versions associated to $ρ$, and the Littlewood-Paley $g$-function associated to $ρ$, where the Littlewood-Paley $g$-function and some of the radial maximal functions are defined via kernels which are modeled on the semigroup generated by the Schrödinger operator. These results apply in a wide range of settings, for instance, to the Schrödinger operator or the degenerate Schrödinger operator on ${\mathbb R}^d$, or the sub-Laplace Schrödinger operator on Heisenberg groups or connected and simply connected nilpotent Lie groups.

math.FA↗

Localized Morrey-Campanato Spaces on Metric Measure Spaces and Applications to Schrödinger Operators

Let ${\mathcal X}$ be a space of homogeneous type in the sense of Coifman and Weiss and ${\mathcal D}$ a collection of balls in $\cx$. The authors introduce the localized atomic Hardy space $H^{p, q}_{\mathcal D}({\mathcal X})$ with $p\in (0,1]$ and $q\in[1,\infty]\cap(p,\infty]$, the localized Morrey-Campanato space ${\mathcal E}^{α, p}_{\mathcal D}({\mathcal X})$ and the localized Morrey-Campanato-BLO space $\widetilde{\mathcal E}^{α, p}_{\mathcal D}({\mathcal X})$ with $\az\in{\mathbb R}$ and $p\in(0, \infty)$ and establish their basic properties including $H^{p, q}_{\mathcal D}({\mathcal X})=H^{p, \infty}_{\mathcal D}({\mathcal X})$ and several equivalent characterizations for ${\mathcal E}^{α, p}_{\mathcal D}({\mathcal X})$ and $\wz{\mathcal E}^{α, p}_{\mathcal D}({\mathcal X})$. Especially, the authors prove that when $p\in(0,1]$, the dual space of $H^{p, \infty}_{\mathcal D}({\mathcal X})$ is ${\mathcal E}^{1/p-1, 1}_{\mathcal D}({\mathcal X})$. Let $ρ$ be an admissible function modeled on the known auxiliary function determined by the Schrödinger operator. Denote the spaces ${\mathcal E}^{α, p}_{\mathcal D}({\mathcal X})$ and $\widetilde{\mathcal E}^{α, p}_{\mathcal D}({\mathcal X})$, respectively, by ${\mathcal E}^{α, p}_ρ({\mathcal X})$ and $\widetilde{\mathcal E}^{α, p}_ρ({\mathcal X})$, when ${\mathcal D}$ is determined by $ρ$. The authors then obtain the boundedness from ${\mathcal E}^{α, p}_ρ({\mathcal X})$ to $\widetilde{\mathcal E}^{α, p}_ρ({\mathcal X})$ of the radial and the Poisson semigroup maximal functions and the Littlewood-Paley $g$-function which are defined via kernels modeled on the semigroup generated by the Schrödinger operator.

math.CA↗

Boundedness of Linear Operators via Atoms on Hardy Spaces with Non-doubling Measures

Let $μ$ be a non-negative Radon measure on ${\mathbb R}^d$ which only satisfies the polynomial growth condition. Let ${\mathcal Y}$ be a Banach space and $H^1(μ)$ the Hardy space of Tolsa. In this paper, the authors prove that a linear operator $T$ is bounded from $H^1(μ)$ to ${\mathcal Y}$ if and only if $T$ maps all $(p, γ)$-atomic blocks into uniformly bounded elements of ${\mathcal Y}$; moreover, the authors prove that for a sublinear operator $T$ bounded from $L^1(μ)$ to $L^{1, \infty}(μ)$, if $T$ maps all $(p, γ)$-atomic blocks with $p\in(1, \infty)$ and $γ\in{\mathbb N}$ into uniformly bounded elements of $L^1(μ)$, then $T$ extends to a bounded sublinear operator from $H^1(μ)$ to $L^1(μ)$. For the localized atomic Hardy space $h^1(μ)$, corresponding results are also presented. Finally, these results are applied to Calderón-Zygmund operators, Riesz potentials and multilinear commutators generated by Calderón-Zygmund operators or fractional integral operators with Lipschitz functions, to simplify the existing proofs in the corresponding papers.

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