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We present some new bounds for the first Robin eigenvalue with a negative boundary parameter. These include the constant volume problem, where the bounds are based on the shrinking coordinate method, and a proof that in the fixed perimeter…

Spectral Theory · Mathematics 2018-11-26 Pedro R. S. Antunes , Pedro Freitas , David Krejcirik

We consider the eigenvalues of the Laplacian on an open, bounded, connected set in $\mathbb{R}^n$ with $C^2$ boundary, with a Neumann boundary condition or a Robin boundary condition. We obtain upper bounds for those eigenvalues that have a…

Spectral Theory · Mathematics 2026-02-19 Katie Gittins , Corentin Léna

A numerical study of the nonlinear Schr\"odinger (NLS) equation subject to homogeneous Dirichlet, Neumann and Robin boundary conditions in the finite line is presented. The results are compared with both the exact analytical ones for the…

Pattern Formation and Solitons · Physics 2013-01-18 Juan I. Ramos , Francisco R. Villatoro

In this paper, we consider the Laplace equation with a class of indefinite superlinear boundary conditions and study the uniqueness of positive solutions that this problem possesses. Superlinear elliptic problems can be expected to have…

Analysis of PDEs · Mathematics 2024-01-22 Kenichiro Umezu

In this paper we first introduce an innovative equivalent norm in the Musielak-Orlicz Sobolev spaces in a very general setting and we then present a new result on the boundedness of the solutions of a wide class of nonlinear Neumann…

Analysis of PDEs · Mathematics 2024-11-12 Eleonora Amoroso , Ángel Crespo-Blanco , Patrizia Pucci , Patrick Winkert

We study the solvability of boundary-value problems for differential-operator equations of the second order in L p (0, 1; X), with 1 < p < +$\infty$, X being a UMD complex Banach space. The originality of this work lies in the fact that we…

Analysis of PDEs · Mathematics 2025-09-18 Angelo Favini , Rabah Labbas , Stéphane Maingot , Alexandre Thorel

A second-order regularity theory is developed for solutions to a class of quasilinear elliptic equations in divergence form, including the $p$-Laplace equation, with merely square-integrable right-hand side. Our results amount to the…

Analysis of PDEs · Mathematics 2018-05-23 Andrea Cianchi , Vladimir Maz'ya

This paper is concerned with a Neumann type problem for singularly perturbed fractional nonlinear Schr\"odinger equations with subcritical exponent. For some smooth bounded domain $\Omega\subset \mathbf R^n$, our boundary condition is given…

Analysis of PDEs · Mathematics 2016-11-22 Guoyuan Chen

Let $\Omega\subset\mathbb{R}^n$ with $n\ge 2$ be a bounded Lipschitz domain with outer unit normal $\nu$. For $\alpha\in\mathbb{R}$ let $R_\Omega^\alpha$ be the Laplacian in $\Omega$ with the Robin boundary condition $\partial_\nu u+\alpha…

Spectral Theory · Mathematics 2025-09-29 Charlotte Dietze , Konstantin Pankrashkin

We prove well-posedness and higher-order regularity for a linear structurally damped plate equation with inhomogeneous Dirichlet--Neumann boundary conditions on the half-space and on bounded domains. To this end, we study maximal regularity…

Analysis of PDEs · Mathematics 2026-03-02 Robert Denk , Floris Roodenburg

We introduce a new Neumann problem for the fractional Laplacian arising from a simple probabilistic consideration, and we discuss the basic properties of this model. We can consider both elliptic and parabolic equations in any domain. In…

Analysis of PDEs · Mathematics 2014-11-03 Serena Dipierro , Xavier Ros-Oton , Enrico Valdinoci

Recently Rohleder proposed a new variational approach to an inequality between the Neumann and Dirichlet eigenvalues in the simply connected planar case using the language of classical vector analysis. Writing his approach in terms of…

Differential Geometry · Mathematics 2025-01-30 Muravyev Mikhail

The spectral gap of the Neumann and Dirichlet Laplacians are each known to have a sharp positive lower bound among convex domains of a given diameter. Between these cases, for each positive value of the Robin parameter an analogous sharp…

Spectral Theory · Mathematics 2022-03-29 Derek Kielty

We consider the Laplace equation in a cracked plane with a nonclassical boundary conditions. This problem arises as a model of the flow in the fractured media. The main result is the theorem of existence and uniqueness of a solution in…

Analysis of PDEs · Mathematics 2025-12-16 Mykola Krasnoshchok

We consider the cases where there is equality in Courant's nodal domain theorem for the Laplacian with a Robin boundary condition on the square. In our previous two papers, we treated the cases where the Robin parameter $h>0$ is large,…

Spectral Theory · Mathematics 2020-03-31 Katie Gittins , Bernard Helffer

This article is the continuation of our first work on the determination of the cases where there is equality in Courant's Nodal Domain theorem in the case of a Robin boundary condition (with Robin parameter $h$). For the square, our first…

Spectral Theory · Mathematics 2019-03-27 Katie Gittins , Bernard Helffer

We study the inverse problem for the fractional Laplace equation with multiple nonlinear lower order terms. We show that the direct problem is well-posed and the inverse problem is uniquely solvable. More specifically, the unknown…

Analysis of PDEs · Mathematics 2020-09-18 Ru-Yu Lai , Laurel Ohm

In this paper, we investigate the existence and uniqueness of solutions for the following model problem, involving singularities and inhomogeneous Robin boundary conditions \begin{equation*} \left\{ \begin{array}{ll}…

Analysis of PDEs · Mathematics 2024-10-29 Mohamed El Hichami , Youssef El Hadfi

This paper addresses the geometric optimization problem of the first Robin eigenvalue in exterior domains, specifically the lowest point of the spectrum of the Laplace operator under Robin boundary conditions in the complement of a bounded…

Analysis of PDEs · Mathematics 2024-04-18 Lukas Bundrock

We announce a new result which shows that under either Dirichlet, Neumann, or Robin boundary conditions, the corners in a planar domain are a spectral invariant of the Laplacian. For the case of polygonal domains, we show how a locality…

Spectral Theory · Mathematics 2020-12-08 Medet Nursultanov , Julie Rowlett , David Sher