Hartmut Fuehr
The paper studies Hausdorff-Young inequalities for certain group extensions, by use of Mackey's theory. We consider the case in which the dual action of the quotient group is free almost everywhere. This result applies to yield a Hausdorff-Young inequality for nonunimodular groups.
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In this paper we prove new inequalities describing the relationship between the "size" of a function on a compact homogeneous manifold and the "size" of its Fourier coefficients. These inequalities can be viewed as noncommutative versions of the Hardy-Littlewood inequalities obtained by Hardy and Littlewood on the circle. For the example case of the group SU(2) we show that the obtained Hardy-Littlewood inequalities are sharp, yielding a criterion for a function to be in $L^p$ on SU(2) in terms of its Fourier coefficients. We also establish Paley and Hausdorff-Young-Paley inequalities on gener…
The classical Hausdorff-Young inequalities for the Fourier transform acting between appropriate $L_p$ spaces are cornerstones of Fourier analysis. Here we extend it to weighted spaces of Besov or Sobolev type where the weight has the form $w(x)=(1+|x|^2)^{α/2}$. This note is not a paper or draft but a sketchy complement to some earlier results where we dealt with mapping properties of the Fourier transform.
We study Hausdorff-Young type inequalities for vector-valued Dirichlet series which allow to compare the norm of a Dirichlet series in the Hardy space $\mathcal{H}_{p} (X)$ with the $q$-norm of its coefficients. In order to obtain inequalities completely analogous to the scalar case, a Banach space must satisfy the restrictive notion of Fourier type/cotype. We show that variants of these inequalities hold for the much broader range of spaces enjoying type/cotype. We also consider Hausdorff-Young type inequalities for functions defined on the infinite torus $\mathbb{T}^{\infty}$ or the boolean …
The aim of this paper is to study the sharp bounds of rough Hausdorff operators on the product of Herz, central Morrey and Morrey-Herz spaces with both power weights and Muckenhoupt weights on the Heisenberg group. Especially, by applying the block decomposition of the Herz space, we obtain the boundedness of rough Hausdorff operator in the case 0 < p < 1. In addition, the boundedness for the commutators of rough Hausdorff operators on such spaces with symbols in weighted central BMO space is also established.
In this paper we study the vector-valued analogues of several inequalities for the Fourier transform. In particular, we consider the inequalities of Hausdorff--Young, Hardy--Littlewood, Paley, Pitt, Bochkarev and Zygmund. The Pitt inequalities include the Hausdorff--Young and Hardy--Littlewood inequalities and state that the Fourier transform is bounded from $L^p(\mathbb{R}^d,|\cdot|^{βp})$ into $L^q(\mathbb{R}^d,|\cdot|^{-γq})$ under certain condition on $p,q,β$ and $γ$. Vector-valued analogues are derived under geometric conditions on the underlying Banach space such as Fourier type and rela…
Dunkl-Hausdorff operator on weighted Orlicz spaces
本文在加权Orlicz空间中刻画了作用于非负非增函数的Dunkl-Hausdorff算子的模不等式与范数不等式，揭示了该算子的有界性特征。
$L^p$-$L^q$ Fourier multipliers and Hausdorff-Young-Paley inequalities on Riemannian symmetric spaces of noncompact type
本文在任意秩非紧型黎曼对称空间上建立Hörmander型Lp-Lq Fourier乘子定理，推导谱乘子定理，证明Laplace-Beltrami算子函数的有界性，并给出Hausdorff-Young和Paley不等式的混合范数版本，结果适用于Damek-Ricci空间。
We obtain several versions of the Hausdorff-Young and Hardy-Littlewood inequalities for the $(k,a)$-generalized Fourier transform recently investigated at length by Ben Saï d, Kobayashi, and Ø rsted. We also obtain a number of weighted inequalities - in particular Pitt's inequality - that have application to uncertainty principles. Specifically we obtain several analogs of the Heisenberg-Pauli-Weyl principle for $L^p$-functions, local Cowling-Price-type inequalities, Donoho-Stark-type inequalities and qualitative extensions. We finally use the Hausdorff-Young inequality as a means to obtain en…
A note on Sobolev inequalities in the lower limit case
本文研究了欧几里得空间中光滑函数的Poincaré-Sobolev型不等式，探讨了梯度绝对值关于δ维Hausdorff内容的Choquet δ/n可积性，并推导了Sobolev空间中quasicontinuous函数的新Sobolev不等式。
Sharp Poincaré--Sobolev Inequalities of Choquet--Lorentz Integrals with Respect to Hausdorff Contents on Bounded John Domains
本文证明了有界 John 域上关于 Hausdorff 容度的 Choquet--Lorentz 积分具有精确指数范围的 Poincaré--Sobolev 不等式，发展了分数阶极大不等式等新工具，并给出了临界情形的端点估计及 Riesz 位势的精确有界性。
We consider integral inequalities in the sense of Choquet with respect to the Hausdorff content $\mathcal{H}_\infty^δ$. In particular, if $Ω$ is a bounded John domain in $\mathbb{R}^n$, $n\geq 2$, and $0 <δ\le n$, we prove that the corresponding $(δp/(δ-p),p)$-Poincaré-Sobolev inequalities hold for all continuously differentiable functions defined on $Ω$ whenever $δ/n < p < δ$. We prove also that the $(p,p)$-Poincaré inequality is valid for all $p>δ/n$.
Classical inequalities for all Fourier matrix coefficients of $\mathrm{SL}(2,\mathbb{R})$ and their applications
本文为 $\mathrm{SL}(2,\mathbb{R})$ 上的 $(l, n)$ 型函数建立了三个基础 Fourier 不等式，据此证明了 Fourier 乘子的 $L^p$-$L^q$ 有界性，并将其应用于热核估计与非线性方程的全局适定性研究。
In this paper, we considered the problem of finding the upper bound Hausdorff matrix operator from sequence spaces $l_p(v)$ (or $d(v,p)$) into $l_p(w)$ (or $d(w,p)$). Also we considered the upper bound problem for matrix operators from $d(v,1)$ into $d(w,1)$, and matrix operators from $e(w,\infty)$ into $e(v,\infty)$, and deduce upper bound for Cesaro, Copson and Hilbert matrix operators, which are recently considered in \cite{5} and \cite{6} and similar to that in \cite{10}.
Hausdorff content $A_p$ weights: weighted maximal inequalities and fundamental structural properties
本文研究了容积穆肯霍普特权重与Hardy-Littlewood极大算子的加权范数不等式，建立了新的权重类并验证了经典Muckenhoupt权重的若干性质。
Brascamp--Lieb inequalities for fractal dimensions
本文利用泛函分析中的Brascamp--Lieb不等式，证明了关于分形集的上盒维数、包络维数和Assouad维数的新不等式，这些不等式以某些投影的维数为条件。与Hausdorff和下盒维数不同，类似不等式不成立。作者将这些分形Brascamp--Lieb不等式应用于正交投影的例外集估计，并为某些受限和集提供精确的维数估计，同时通过非线性Brascamp--Lieb不等式建立了类似的非线性不等式。
On Choquet integrals and pointwise estimates
本文研究关于Hausdorff内容的Choquet积分不等式，在开连通集上具有足够正则性的连续可微函数满足逐点估计条件，证明了Hardy不等式和Poincare-Sobolev不等式在该背景下成立。
On Choquet integrals and Sobolev type inequalities
本文研究n维欧氏空间开连通集上连续可微函数关于δ维Hausdorff容度的Choquet积分，证明了p=δ/n极限情形与p>δ情形的Sobolev型不等式，补充了已有的Poincaré-Sobolev和Morrey不等式。
Analog version of Hausdorff--Young's theorem for quadratic Fourier transforms and boundedness of oscillatory integral operator
本文基于 Riesz--Thorin 插值定理证明了二次 Fourier 变换和线性正则变换的 Hausdorff--Young 型不等式，并研究了多项式相位振荡积分算子的有界性。
This paper deals with the inequalities devoted to the comparison between the norm of a function on a compact hypergroup and the norm of its Fourier coefficients. We prove the classical Paley inequality in the setting of compact hypergroups which further gives the Hardy-Littlewood and Hausdorff-Young-Paley (Pitt) inequalities in the noncommutative context. We establish Hörmander's $L^p$-$L^q$ Fourier multiplier theorem on compact hypergroups for $1<p \leq 2 \leq q<\infty$ as an application of Hausdorff-Young-Paley inequality. We examine our results for the hypergroups constructed from the conju…
Noncommutative sharp Hausdorff-Young inequality
本文在量子欧几里得空间上证明了尖锐Hausdorff-Young不等式，并推导出Weyl变换和海森堡群的相应常数，方法基于算子演算和Gabor变换相关的新型算子值流，同时定义了非交换卷积并给出Young不等式的部分结果。
We present geometric conditions on a metric space $(Y,d_Y)$ ensuring that almost surely, any isometric action on $Y$ by Gromov's expander-based random group has a common fixed point. These geometric conditions involve uniform convexity and the validity of nonlinear Poincaré inequalities, and they are stable under natural operations such as scaling, Gromov-Hausdorff limits, and Cartesian products. We use methods from metric embedding theory to establish the validity of these conditions for a variety of classes of metric spaces, thus establishing new fixed point results for actions of Gromov's "…
We establish sharp Sobolev embedding properties within a broad class of compact matrix quantum groups of Kac type under the polynomial growth or the rapid decay property of their duals. Main examples are duals of polynomially growing discrete quantum groups, duals of free groups and free quantum groups $O_N^+,S_N^+$. In addition, we generalize sharpend Hausdorff-Young inequalities, compute degrees of the rapid decay property for $\widehat{O_N^+},\widehat{S_N^+}$ and prove sharpness of Hardy-Littlewood inequalities on duals of free groups.
Fourier theoretic inequalities for inclusion of simple C*-algebras
本文研究了简单C*-代数包含关系中的非交换傅里叶理论不等式，证明了Hirschman-Beckner和Donoho-Stark不确定性原理，并推广了Jiang等人之前的结果。
In this paper, we establish some reverses of the operator entropy inequalities under certain conditions by using the Mond-Pečarić method. In particular, we present {\tiny \begin{align*} f&\left[\int_T(A_s\natural_{p+1}B_s)dμ(s)+t_0\left(I_{\mathscr H}-\int_TA_s\natural_pB_sdμ(s)\right)\right]-γ_ff(t_0)\left(I_{\mathscr H}-\int_TA_s\natural_pB_sdμ(s)\right)\nonumber\\ &\le γ_f\widetilde{S}_p^f(\mathbf{A}|\mathbf{B})\,, \end{align*}} where $T$ is a locally compact Hausdorff space and $μ$ is a Radon measure on $T$, $0<m A_s \leq B_s \leq M A_s\,\,(s\in T)$ for some positive real numbers $m, M$ su…
We establish a general operator parallelogram law concerning a characterization of inner product spaces, get an operator extension of Bohr's inequality and present several norm inequalities. More precisely, let ${\mathfrak A}$ be a $C^*$-algebra, $T$ be a locally compact Hausdorff space equipped with a Radon measure $μ$ and let $(A_t)_{t\in T}$ be a continuous field of operators in ${\mathfrak A}$ such that the function $t \mapsto A_t$ is norm continuous on $T$ and the function $t \mapsto \|A_t\|$ is integrable. If $α: T \times T \to \mathbb{C}$ is a measurable function such that $\bar{α(t,s)}…
On Herz-Bochkarev limiting problem
本文利用新型 grand Lorentz 空间技术研究 $L_{p,q}$ 中 Hausdorff-Young 型不等式常数随 $p$ 的变化，得出 $p\ ightarrow 2$ 极限情形的最优界，解决 Herz-Bochkarev 问题并改进已有估计。
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