Sharp Bounds for the Harmonic Numbers

Sharp Strichartz type estimates for the Schrödinger equation associated with harmonic oscillator

In this article we study the Schrödinger equation associated with Harmonic oscillator in the form of Strichartz type inequality. We give simple proofs for Strichartz type inequalities using purely the $L^2 \to L^p$ operator norm estimates of the spectral projections associated harmonic oscillator proved in \cite{KT}. Our Strichartz type estimates are sharp in sense of regularity of initial data.

Sharp inequalities for the Neuman-Sandor mean in terms of arithmetic and contra-harmonic means

In this paper, we find the greatest values $α$ and $λ$, and the least values $β$ and $μ$ such that the double inequalities $$C^α(a,b)A^{1-α}(a,b)<M(a,b)<C^β(a,b)A^{1-β}(a,b)$$ and &[C(a,b)/6+5 A(a,b)/6]^λ[C^{1/6}(a,b)A^{5/6}(a,b)]^{1-λ}<M(a,b) &\qquad<[C(a,b)/6+5 A(a,b)/6]^μ[C^{1/6}(a,b)A^{5/6}(a,b)]^{1-μ} hold for all $a,b>0$ with $a\neq b$, where $M(a,b)$, $A(a,b)$ and $C(a,b)$ denote the Neuman-Sándor, arithmetic, and contra-harmonic means of $a$ and $b$, respectively.

Sharp Inequalities between Harmonic, Seiffert, Quadratic and Contraharmonic Means

In this paper, we present the greatest values $α$, $λ$ and $p$, and the least values $β$, $μ$ and $q$ such that the double inequalities $αD(a,b)+(1-α)H(a,b)<T(a,b)<βD(a,b)+(1-β) H(a,b)$, $λD(a,b)+(1-λ)H(a,b)<C(a,b)<μD(a,b)+(1-μ) H(a,b)$ and $p D(a,b)+(1-p)H(a,b)<Q(a,b)<q D(a,b)+(1-q)H(a,b)$ hold for all $a,b>0$ with $a\neq b$, where $H(a,b)=2ab/(a+b)$, $T(a,b)=(a-b)/[2\arctan((a-b)/(a+b))]$, $Q(a,b)=\sqrt{(a^2+b^2)/2}$, $C(a,b)=(a^2+b^2)/(a+b)$ and $D(a,b)=(a^3+b^3)/(a^2+b^2)$ are the harmonic, Seiffert, quadratic, first contraharmonic and second contraharmonic means of $a$ and $b$, respective…

一维谐振子的高斯型急剧衰减

Sharp Gaussian decay for the one-dimensional harmonic oscillator

本文通过 Plancherel-Rotach 渐近公式和局部极值分析，证明了一维谐振子 Hermite 函数带指数衰减权重的 $\ell^κ$ 和具有高斯型急剧衰减上界，从而证实了 Vemuri 的猜想。

Some sharp inequalities involving Seiffert and other means and their concise proofs

In the paper, by establishing the monotonicity of some functions involving the sine and cosine functions, the authors provide concise proofs of some known inequalities and find some new sharp inequalities involving the Seiffert, contra-harmonic, centroidal, arithmetic, geometric, harmonic, and root-square means of two positive real numbers $a$ and $b$ with $a\ne b$.

Lower bound for the Green energy of point configurations in harmonic manifolds

In this paper, we get the sharpest known to date lower bounds for the minimal Green energy of the compact harmonic manifolds of any dimension.

调和延拓的精确量化积分不等式

Sharp quantitative integral inequalities for harmonic extensions

本文针对Poisson算子及其伴随算子，证明了Hang、Wang和Yan的精确积分不等式的量化版本，获得了最强范数和不一定等于2的最优稳定性指数。

对共轭函数的精确估计及其在三角多项式中的应用

Sharp Estimates for Conjugate Functions with Applications to Trigonometric Polynomials

本文通过半带状区域内的调和上界，对共轭函数进行精确估计，并应用于去除Papadopoulos关于三角多项式极小值定理中的对数损失，获得相应不等式的最优阶。

Mapping properties of fundamental operators in harmonic analysis related to Bessel operators

We prove sharp power-weighted strong type, weak type and restricted weak type inequalities for the heat and Poisson integral maximal operators, Riesz transform and a Littlewood-Paley type square function, emerging naturally in the harmonic analysis related to Bessel operators.

调和函数的几个精确估计及其在 Steklov 特征函数中的应用

A few sharp estimates of harmonic functions with applications to Steklov eigenfunctions

本文结合微局部分析与频率函数技术，建立了光滑紧流形上调和函数限制的精确下界，并通过构造参数化分析其内部行为，最终应用于 Steklov 特征函数的估计与调和函数的数值逼近。

Reverse Hölder's inequality for spherical harmonics

This paper determines the sharp asymptotic order of the following reverse Hölder inequality for spherical harmonics $Y_n$ of degree $n$ on the unit sphere $\mathbb{S}^{d-1}$ of $\mathbb{R}^d$ as $n\to \infty$: \[\|Y_n\|_{L^q(\mathbb{S}^{d-1})}\leq C n^{α(p,q)}\|Y_n\|_{L^p(\mathbb{S}^{d-1})},\quad 0<p<q\leq \infty.\] In many cases, these sharp estimates turn out to be significantly better than the corresponding estimates in the Nilkolskii inequality for spherical polynomials. Furthermore, they allow us to improve two recent results on the restriction conjecture and the sharp Pitt inequalities f…

Sharp commutator estimates via harmonic extensions

We give an alternative proof of several sharp commutator estimates involving Riesz transforms, Riesz potentials, and fractional Laplacians. Our methods only involve harmonic extensions to the upper half-space, integration by parts, and trace space characterizations. The commutators we investigate are Jacobians, more generally Coifman-Rochberg-Weiss commutators, Chanillo's commutator with the Riesz potential, Coifman-Meyer or Kato-Ponce-Vega type commutators, and the Da Lio-Rivière three-term commutators. We also give a new limiting $L^1$-estimate for a double commutator of Coifman-Rochberg-Wei…

$p$-调和函数的单调量与尖锐 $p$-Penrose 不等式

Monotone Quantities for $p$-Harmonic functions and the Sharp $p$-Penrose inequality

本文在带极小边界的渐近平坦三维流形上建立 $p$-调和函数的单调量，并据此推出联系 ADM 质量与边界 $p$-容量的尖锐 $p$-Penrose 不等式。

关于涉及调和数与斜调和数的若干级数

On Some Series Involving Harmonic and Skew-Harmonic Numbers

本文以闭式形式评估了涉及调和数与斜调和数的两类级数，解决了两个开放问题，并研究了Hardy级数。

A new family of sharp conformally invariant integral inequalities

We prove a one-parameter family of sharp integral inequalities for functions on the $n$-dimensional unit ball. The inequalities are conformally invariant, and the sharp constants are attained for functions that are equivalent to a constant function under conformal transformations. As a limiting case, we obtain an inequality that generalizes Carleman's inequality for harmonic functions in the plane to poly-harmonic functions in higher dimensions.

二次、算术和调和平均差之比的最优界

Optimal bounds for the ratio of differences of quadratic, arithmetic, and harmonic means

研究\(n\)个非负实数二次、算术和调和平均差之比的最优界，采用基于Cauchy和Maclaurin经典优化方法变体，证明\(n\geq3\)时的双重不等式，扩展了T. Mitev仅针对\(n = 3、4、5\)的结果。

Inequalities for finite trigonometric sums. An interplay: with some series related to Harmonic numbers

An interplay between the sum of certain series related to Harmonic numbers and certain finite trigonometric sums is investigated. This allows us to express the sum of these series in terms of the considered trigonometric sums, and permits us to find sharp inequalities bounding these trigonometric sums. In particular, this answers positively an open problem of H. Chen (2010).

On the curvature of level sets of harmonic functions

If a real harmonic function inside the open unit disk $B(0,1) \subset \mathbb{R}^2$ has its level set $\left\{x: u(x) = u(0)\right\}$ diffeomorphic to an interval, then we prove the sharp bound $κ\leq 8$ on the curvature of the level set $\left\{x: u(x) = u(0)\right\}$ in the origin. The bound is sharp and we give the unique (up to symmetries) extremizer.

Mapping properties of fundamental harmonic analysis operators in the exotic Bessel framework

We prove sharp power-weighted $L^p$, weak type and restricted weak type inequalities for the heat semigroup maximal operator and Riesz transforms associated with the Bessel operator $B_ν$ in the exotic range of the parameter $-\infty < ν< 1$. Moreover, in the same framework, we characterize basic mapping properties for other fundamental harmonic analysis operators, including the heat semigroup based vertical $g$-function and fractional integrals (Riesz potential operators).

Sharp critical and subcritical trace Trudinger-Moser and Adams inequalities on the upper half spaces

In this paper, we establish the sharp critical and subcritical trace Trudinger-Moser and Adams inequalities on the half spaces and prove the existence of their extremals through the method based on the Fourier rearrangement, harmonic extension and scaling invariance. These trace Trudinger-Moser and Adams inequalities can be considered as the borderline case of the Sobolev trace inequalities of first and higher orders. Furthermore, we show the existence of the least energy solutions for a class of bi-harmonic equations with nonlinear Neumann boundary condition associated with the trace Adams in…

A Note on the Weighted Harmonic-Geometric-Arithmetic Means Inequalities

In this note, we derive non trivial sharp bounds related to the weighted harmonic-geometric-arithmetic means inequalities, when two out of the three terms are known. As application, we give an explicit bound for the trace of the inverse of a symmetric positive definite matrix and an inequality related to the coefficients of polynomials with positive roots.

Ramanujan's Harmonic Number Expansion into Negative Powers of a Triangular Number

An algebraic transformation of the DeTemple-Wang half-integer approximation to the harmonic series produces the general formula and error estimate for the Ramanujan expansion for the nth harmonic number into negative powers of the nth triangular number. We also discuss the history of the Ramanujan expansion for the nth harmonic number as well as sharp estimates of its accuracy, with complete proofs, and we compare it with other approximative formulas.

Some remarks on spherical harmonics

The article contains several observations on spherical harmonics and their nodal sets: a construction for harmonics with prescribed zeroes; a kind of canonical representation of this type for harmonics on $\bbS^2$; upper and lower bounds for nodal length and inner radius (the upper bounds are sharp); precise upper bound for the number of common zeroes of two spherical harmonics on $\bbS^2$; the mean Hausdorff measure on the intersection of $k$ nodal sets for harmonics of different degrees on $\bbS^m$, where $k\leq m$ (in particular, the mean number of common zeroes of $m$ harmonics).