Jesse Ratzkin
In this paper, we use a weighted isoperimetric inequality to give a lower bound on the first Dirichlet eigenvalue of the Laplacian on a bounded domain inside a Euclidean cone. Our bound is sharp, in that only sectors realize it. This result generalizes a lower bound of Payne and Weinberger in two dimensions.
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A Faber-Krahn type argument gives a sharp lower estimate for the first Dirichlet eigenvalue for subdomains of wedge domains in spheres, generalizing the inequality in the plane, found by Payne and Weinberger. An application is an alternative proof to the finiteness of a Brownian motion capture time estimate.
We prove stability results associated with upper bounds for the first eigenvalue of certain second order differential operators of divergence-type on hypersurfaces of the Euclidean space. We deduce some applications to $r$-stability as well as to almost-Einstein hypersurfaces.
Let $Ω= \mathbb R^3 \setminus \bar{K}$, where $K$ is an open bounded domain with smooth boundary $Γ$. Let $V(t) = e^{tG_b},\: t \geq 0,$ be the semigroup related to Maxwell's equations in $Ω$ with dissipative boundary condition $ν\wedge (ν\wedge E)+ γ(x) (ν\wedge H) = 0, γ(x) > 0, \forall x \in Γ.$ We study the case when $γ(x) \neq 1, \: \forall x \in Γ,$ and we establish a Weyl formula for the counting function of the eigenvalues of $G_b$ in a polynomial neighbourhood of the negative real axis.
Some universal inequalities for Dirichlet eigenvalues of the Laplacian on a Euclidean convex domain
本文建立了欧几里得凸域上拉普拉斯算子狄利克雷本征值的两个通用不等式，探讨了相关数学性质。
A note on the distribution of Neumann eigenvalues of the Laplacian on a Euclidean convex domain
本文研究了欧几里得凸域上拉普拉斯算子Neumann特征值的分布，建立了两个通用不等式。
On the eigenvalues of the Laplacian on ellipsoids obtained as perturbation of unit sphere
本文研究二维单位球面扰动所得椭球上的 Laplace 特征值，并在高斯曲率条件下建立其与球面特征值的比较，呼应 Lichnerowicz 定理。
The Dirichlet eigenvalues of the Laplace-Beltrami operator are larger on a flat disc than on any other surface of revoltuion immersed in Euclidean space with the same boundary.
We study eigenvalues of polyharmonic operators on compact Riemannian manifolds with boundary (possibly empty). In particular, we prove a universal inequality for the eigenvalues of the polyharmonic operators on compact domains in a Euclidean space. This inequality controls the $k$th eigenvalue by the lower eigenvalues, independently of the particular geometry of the domain. Our inequality is sharper than the known Payne-Pólya-Weinberg type inequality and also covers the important Yang inequality on eigenvalues of the Dirichlet Laplacian. We also prove universal inequalities for the lower order…
In this article we will explore Dirichlet Laplace eigenvalues on balls on spherically symmetric manifolds. We will compare any Dirichlet Laplace eigenvalue with the corresponding Dirichlet Laplace eigenvalue on balls in Euclidean space with the same radius. As a special case we will show that the Dirichlet Laplace eigenvalues on balls with small radius on the sphere are smaller than the corresponding eigenvalues on the Euclidean ball with the same radius. While the opposite is true for the Dirichlet Laplace eigenvalues of hyperbolic spaces.
We investigate the eigenvalues of the buckling problem of arbitrary order on compact domains in Euclidean spaces and spheres. We obtain universal bounds for the $k$th eigenvalue in terms of the lower eigenvalues independently of the particular geometry of the domain.
Improved lower bounds for Dirichlet eigenvalues of the Laplacian and poly-Laplacian on bounded Euclidean domains
本文改进了Dirichlet特征值的下界，通过推导两种二元多项式展开式，优化了现有下界，并证明所获下界在正项捕获上更全面。
Geometric bounds for Steklov and weighted Neumann eigenvalues on Euclidean domains
研究在欧几里得空间中维数d≥3的有界域的前两个非零Steklov特征值的上界，并证明当d≥7时这些界是最佳的。
In this paper, we study eigenvalues of the poly-Laplacian with arbitrary order on a bounded domain in an $n$-dimensional Euclidean space and obtain a lower bound for eigenvalues, which gives an important improvement of results due to Levine and Protter. In particular, the result of Melas is included here.
We prove a sharp upper bound and a lower bound for the first nonzero eigenvalue of the Wentzell-Laplace operator on compact manifolds with boundary and an isoperimetric inequality for the same eigenvalue in the case where the manifold is a bounded domain in a Euclidean space. We study some fourth order Stekolv problems and obtain isoperimetric upper bound for the first eigenvalue of them. We also find all the eigenvalues and eigenfunctions for two kind of fourth order Stekolv problems on a Euclidean ball.
In this paper, we mainly study eigenvalue problems of p-Laplacian on domains with an interior hole. Firstly we prove Faber-Krahn-type inequalities, and Cheng-type eigenvalue comparison theorems on manifolds. Secondly, we prove a comparison theorem for eigenvalues with inner Dirichlet and outer Neumann boundary in minimal submanifolds in Euclidean space. Lastly we give a sharp estimate of the eigenvalue (with outer Dirichlet and inner Neumann boundaries) in terms of the Dircihlet eigenvalue, and also we give an upper bound of the eigenvalue with inner Dirichlet and outer Neumann problems by the…
Adapting the method of Andrews-Clutterbuck we prove an eigenvalue gap theorem for a class of non symmetric second order linear elliptic operators on a convex domain in euclidean space. The class of operators includes the Bakry-Emery laplacian with potential and any operator with second order term the laplacian whose first order terms have coefficients with compact support in the open domain. The eigenvalue gap is bounded below by the gap of an associated Sturm-Liouville problem on a closed interval.
We show several results comparing sharp eigenvalue bounds for the first Steklov eigenvalue on surfaces under change of the topology. Among others, we obtain strict monotonicity in the genus. Combined with results of the second named author \cite{petrides_2} this implies the existence of free boundary minimal immersions from higher genus surfaces into Euclidean balls. Moreover, we can also give a new proof of a result by Fraser and Schoen that shows monotonicity in the number of boundary components.
On shape optimization for fourth order Steklov eigenvalue problems
本文研究了三类四阶Steklov特征值问题，推导了前两类问题在欧氏环形区域上的谱渐近展开以得出形状优化结论，计算了其在闭Riemannian流形柱体上的谱，并为第三类问题在星形与平均凸欧氏区域上获得了首个非零特征值的精确上界。
For any compact surface $Σ$ with smooth, non-empty boundary, we construct a free boundary minimal immersion into a Euclidean Ball $\mathbb{B}^N$ where $N$ is controlled in terms of the topology of $Σ$. We obtain these as maximizing metrics for the isoperimetric problem for the first non-trivial Steklov eigenvalue. Our main technical result concerns asymptotic control on eigenvalues in a delicate glueing construction which allows us to prove the remaining spectral gap conditions to complete the program by Fraser--Schoen and the second named author to obtain such mazimizing metrics. Our construc…
} In this article, we put forward a Neumann eigenvalue problem for the bi-harmonic operator $Δ^2$ on a bounded smooth domain $\Om$ in the Euclidean $n$-space ${\bf R}^n$ ($n\ge2$) and then prove that the corresponding first non-zero eigenvalue $Υ_1(\Om)$ admits the isoperimetric inequality of Szegö-Weinberger type: $Υ_1(\Om)\le Υ_1(B_{\Om})$, where $B_{\Om}$ is a ball in ${\bf R}^n$ with the same volume of $\Om$. The isoperimetric inequality of Szegö-Weinberger type for the first nonzero Neumann eigenvalue of the even-multi-Laplacian operators $Δ^{2m}$ ($m\ge1$) on $\Om$ is also exploited.
We consider an isoperimetric problem involving the smallest positive and largest negative curl eigenvalues on abstract ambient manifolds, with a focus on the standard model spaces. We in particular show that the corresponding eigenvalues on optimal domains, assuming optimal domains exist, must be simple in the Euclidean and hyperbolic setting. This generalises a recent result by Enciso and Peralta-Salas who showed the simplicity for axisymmetric optimal domains with connected boundary in Euclidean space. We then generalise another recent result by Enciso and Peralta-Salas, namely that the poin…
We obtain sharp lower bounds for the first eigenvalue of four types of eigenvalue problem defined by the bi-Laplace operator on compact manifolds with boundary and determine all the eigenvalues and the corresponding eigenfunctions of a Wentzell-type bi-Laplace problem on Euclidean balls.
This paper is concerned with the Dirichlet eigenvalue problem associated to the $\infty$-Laplacian in metric spaces. We establish a direct PDE approach to find the principal eigenvalue and eigenfunctions in a proper geodesic space without assuming any measure structure. We provide an appropriate notion of solutions to the $\infty$-eigenvalue problem and show the existence of solutions by adapting Perron's method. Our method is different from the standard limit process via the variational eigenvalue formulation for $p$-Laplacian in the Euclidean space.
New isoperimetric inequalities for lower order eigenvalues of the Laplacian on closed hypersurfaces, of the biharmonic Steklov problems and of the Wentzell-Laplace on bounded domains in a Euclidean space are proven. Some open questions for further study are also proposed.
In this paper, we prove an isoperimetric inequality for lower order eigenvalues of the free membrane problem on bounded domains of a Euclidean space or a hyperbolic space which strengthens the well-known Szegö-Weinberger inequality and supports strongly an important conjecture of Ashbaugh-Benguria.
The exterior Steklov problem for Euclidean domains
研究欧几里得外部区域上的Steklov特征值问题，给出多种等价表述，并证明凸域上第一外部Steklov特征值的Escobar型下界，该下界由边界主曲率表示且对球达到最优。
In this paper, we establish several inequalities of Dirichlet eigenvalues for Laplace operator $Δ$ with any order on \emph{n}-dimensional Euclidean space. These inequalities are more general than known Yang's inequalities and contain new consequences. To obtain them, we borrow the approach of Illias and Makhoul, and use a generalized Chebyshev's inequality.
Pólya's Conjecture for the Neumann Eigenvalues on Euclidean Balls
研究欧几里得球上诺伊曼拉普拉斯算子的波利亚猜想下界，通过严格罗宾比较、变分界等方法，在不同频率范围进行估计，最终证明该猜想，有限有理计算辅助证明。
In this paper, we prove an isoperimetric inequality for lower order eigenvalues of the Dirichlet Laplacian on bounded domains of a Euclidean space which strengthens the well-known Ashbaugh-Beguria inequality conjectured by Payne-Pólya-Weinberger on the ratio of the first two Dirichlet eigenvalues and makes an important step toward the proof of a conjecture by Ashbaugh-Benguria.
We study the eigenvalue problem for the Riemannian Pucci operator on geodesic balls. We establish upper and lower bounds for the principal Pucci eigenvalues depending on the curvature, extending Cheng's eigenvalue comparison theorem for the Laplace-Beltrami operator. For manifolds with bounded sectional curvature, we prove Cheng's bounds hold for Pucci eigenvalues on geodesic balls of radius less than the injectivity radius. For manifolds with Ricci curvature bounded below, we prove Cheng's upper bound holds for Pucci eigenvalues on certain small geodesic balls. We also prove that the principa…
In this paper, we prove the uniform estimates for the resolvent $(Δ- α)^{-1}$ as a map from $L^q$ to $L^{q'}$ on real hyperbolic space $\mathbb{H}^n$ where $α\in \mathbb{C}\setminus [(n - 1)^2/4, \infty)$ and $2n/(n + 2) \leq q < 2$. In contrast with analogous results on Euclidean space $\mathbb{R}^n$, the exponent $q$ here can be arbitrarily close to $2$. This striking improvement is due to two non-Euclidean features of hyperbolic space: the Kunze-Stein phenomenon and the exponential decay of the spectral measure. In addition, we apply this result to the study of eigenvalue bounds of the Schr…
Curl curl versus Dirichlet Laplacian eigenvalues
该研究给出有界三维区域上curl curl算子特征值的Dirichlet拉普拉斯特征值上界估计，补充了其与Neumann拉普拉斯特征值的不等式，对应常参数Maxwell特征值问题。
We show that the eigenvalues of the intrinsic Dirac operator on the boundary of a Euclidean domain can be obtained as the limits of eigenvalues of Euclidean Dirac operators, either in the domain with a MIT-bag type boundary condition or in the whole space, with a suitably chosen zero order mass term.
We propose a method for obtaining rigorous and accurate upper and lower bounds on the eigenvalues of ordinary and partial differential operators in bounded regions of Euclidean space. It uses a boundary condition homotopy method starting from a decomposition of the region into several simpler regions for which the eigenvalues can already be computed accurately. Several numerical examples are presented.
We consider arbitrary open sets $Ω$ in Euclidean space with finite Lebesgue measure, and obtain upper bounds for (i) the largest Courant-sharp Dirichlet eigenvalue of $Ω$, (ii) the number of Courant-sharp Dirichlet eigenvalues of $Ω$. This extends recent results of P. Bérard and B. Helffer.
We study eigenvalues of non-self-adjoint Schrödinger operators on non-trapping asymptotically conic manifolds of dimension $n\ge 3$. Specifically, we are concerned with the following two types of estimates. The first one deals with Keller type bounds on individual eigenvalues of the Schrödinger operator with a complex potential in terms of the $L^p$-norm of the potential, while the second one is a Lieb-Thirring type bound controlling sums of powers of eigenvalues in terms of the $L^p$-norm of the potential. We extend the results of Frank (2011), Frank-Sabin (2017), and Frank-Simon (2017) on th…
This paper studies eigenvalues of the buckling problem of arbitrary order on compact domains in Euclidean spaces and spheres. We prove universal bounds for the $k$-th eigenvalue in terms of the lower ones independent of the domains. Our results strengthens the recent work by Jost, Li-Jost, Wang and Xia and generalizes Cheng-Yang's recent estimates on the buckling eigenvalues of order two to arbitrary order.
Inequalities between Dirichlet and Neumann eigenvalues on Carnot groups
本文证明Carnot群开集上次Laplacian算子的第j个Dirichlet特征值大于第(j+1)个Neumann特征值，推广了Euclidean与Heisenberg情形的早期结果。
We provide isoperimetric Szegö-Weinberger type inequalities for the first nontrivial Neumann eigenvalue $μ_{1}(Ω)$ in Gauss space, where $Ω$ is a possibly unbounded domain of $\mathbb{R}^{N}$. Our main result consists in showing that among all sets of $\mathbb{R}^{N}$ symmetric about the origin, having prescribed Gaussian measure, $μ_{1}(Ω)$ is maximum if and only if $Ω$ is the euclidean ball centered at the origin.
We consider the first eigenvalue $λ_1(Ω,σ)$ of the Laplacian with Robin boundary conditions on a compact Riemannian manifold $Ω$ with smooth boundary, $σ\in\bf R$ being the Robin boundary parameter. When $σ>0$ we give a positive, sharp lower bound of $λ_1(Ω,σ)$ in terms of an associated one-dimensional problem depending on the geometry through a lower bound of the Ricci curvature of $Ω$, a lower bound of the mean curvature of $\partialΩ$ and the inradius. When the boundary parameter is negative, the lower bound becomes an upper bound. In particular, explicit bounds for mean-convex Euclidean do…
For an arbitrary nonempty, open set $Ω\subset \mathbb{R}^n$, $n \in \mathbb{N}$, of finite (Euclidean) volume, we consider the minimally defined higher-order Laplacian $(- Δ)^m\big|_{C_0^{\infty}(Ω)}$, $m \in \mathbb{N}$, and its Krein--von Neumann extension $A_{K,Ω,m}$ in $L^2(Ω)$. With $N(λ,A_{K,Ω,m})$, $λ> 0$, denoting the eigenvalue counting function corresponding to the strictly positive eigenvalues of $A_{K,Ω,m}$, we derive the bound $$ N(λ,A_{K,Ω,m}) \leq (2 π)^{-n} v_n |Ω| \{1 + [2m/(2m+n)]\}^{n/(2m)} λ^{n/(2m)}, \quad λ> 0, $$ where $v_n := π^{n/2}/Γ((n+2)/2)$ denotes the (Euclidean) …
Eigenvalue bounds for Schrödinger operators with complex potentials on compact manifolds
本文证明了紧流形上具有复势的薛定谔算子的特征值界，该界仅依赖于势的$L^q$范数，并在球面和Zoll流形上达到最优，是Frank欧氏结果的类比。
The isoperimetric problem of maximizing all eigenvalues of the Laplacian on a metric tree graph within the class of trees of a given average edge length is studied. It turns out that, up to rescaling, the unique maximizer of the $k$-th positive eigenvalue is the star graph with three edges of lengths $2 k - 1$, $1$ and $1$. This complements the previously known result that the first nonzero eigenvalue is maximized by all equilateral star graphs and indicates that optimizers of isoperimetric problems for higher eigenvalues may be less balanced in their shape -- an observation which is known fro…
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