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In the pass from classical to modern physics, the idea of supposing some quantities having distinct or bounded values and keeping the rest continuous has been useful in treating many problems. In this paper, we suppose an upper limit for…

Solar and Stellar Astrophysics · Physics 2021-07-27 Amir A. E. Shafig

Blazar observations point toward the possible presence of magnetic fields over intergalactic scales of the order of up to $\sim1\,$Mpc, with strengths of at least $\sim10^{-16}\,$G. Understanding the origin of these large-scale magnetic…

Cosmology and Nongalactic Astrophysics · Physics 2020-03-17 Tina Kahniashvili , Axel Brandenburg , Arthur Kosowsky , Sayan Mandal , Alberto Roper Pol

In 1961 G.Polya published a paper about the eigenvalues of vibrating membrane. The "free vibrating membrane"' corresponds to the Neumann-Laplace operator in bounded plane domains. In this paper we obtain estimates for the first eigenvalue…

Analysis of PDEs · Mathematics 2017-03-28 V. Gol'dshtein , A. Ukhlov

We determine a counterexample to strong diamagnetism for the Laplace operator in the unit disc with a uniform magnetic field and Robin boundary condition. The example follows from the accurate asymptotics of the lowest eigenvalue when the…

Spectral Theory · Mathematics 2020-08-26 Ayman Kachmar , Mikael P. Sundqvist

We prove the existence of an open set $\Omega\subset\mathbb{S}^2$ for which the first positive eigenvalue of the Laplacian with Neumann boundary condition exceeds that of the geodesic disk having the same area. This example holds for large…

Analysis of PDEs · Mathematics 2025-03-31 Dorin Bucur , Richard S. Laugesen , Eloi Martinet , Mickaël Nahon

We study the Schroedinger operator with a constant magnetic field in the exterior of a compact domain in $\mathbb{R}^{2d}$, $d\geq 1$. The spectrum of this operator consists of clusters of eigenvalues around the Landau levels. We give…

Mathematical Physics · Physics 2015-05-13 Mikael Persson

Comparing Neumann and Dirichlet eigenvalues of the Laplacian on a bounded domain $\Omega\subseteq\Rbb^n$ is a topic that goes back at least to the work of P\'olya \cite{polya}. We study the effect of the isoperimetric ratio of $\Omega$ on…

Spectral Theory · Mathematics 2025-04-28 Lawford Hatcher

We introduce the notion of discrete cusp for a weighted graph. In this context, we provethat the form-domain of the magnetic Laplacian and that of thenon-magnetic Laplacian can be different. We establish the emptiness of the essential…

Spectral Theory · Mathematics 2017-06-12 Sylvain Golénia , Françoise Truc

We study the $\bar\partial$-Neumann Laplacian from spectral theoretic perspectives. In particular, we show how pseudoconvexity of a bounded domain is characterized by positivity of the $\bar\partial$-Neumann Laplacian.

Complex Variables · Mathematics 2010-06-23 Siqi Fu

It is shown that the electric current of massive fermions along the external magnetic field can be excited in the case when particles possess anomalous magnetic moments and electroweakly interact with background matter. This current is…

High Energy Physics - Phenomenology · Physics 2018-02-15 Maxim Dvornikov

We show that the initial-value problem for the non-relativistic magnetic dynamo equation turns out to be ill-posed when the electromotive force depends linearly on the magnetic field. This result implies that the increasing of magnetic…

High Energy Astrophysical Phenomena · Physics 2021-11-29 Marcelo E. Rubio , Federico A. Stasyszyn

We consider the Ginzburg-Landau functional defined over a bounded and smooth three dimensional domain. Supposing that the magnetic field is comparable with the second critical field and that the Ginzburg-Landau parameter is large, we…

Analysis of PDEs · Mathematics 2011-09-08 S. Fournais , A. Kachmar

Magnetic fields play a crucial role in many astrophysical scenarios and, in particular, are of paramount importance in the emission mechanism and evolution of Neutron Stars (NSs). To understand the role of the magnetic field in compact…

High Energy Astrophysical Phenomena · Physics 2015-06-18 A. G. Pili , N. Bucciantini , L. Del Zanna

The properties of $\Delta$ isobars in a uniform magnetic field are investigated. In the weak magnetic field region, the general relations between magnetic moment of nucleons and $\Delta$ isobars are given. In the strong magnetic field…

High Energy Physics - Phenomenology · Physics 2019-02-27 Bing-Ran He

We analyze the behavior of the eigenvalues and eigenfunctions of the Laplace operator with homogeneous Neumann boundary conditions when the domain is perturbed. We focus on exterior perturbations of the domain, that is, the limit domain is…

Spectral Theory · Mathematics 2011-02-21 Jose M. Arrieta , David Krejcirik

Let $(M,g)$ be a compact Riemannian manifold with a boundary of class $\mathscr{C}^{1}$. We are interested in the spectrum of the weighted Laplacian on $M$ with Neumann boundary conditions. More precisely, given $\rho$ and $\sigma$ two…

Spectral Theory · Mathematics 2019-08-15 Salam Kouzayha , Luc Pétiard

We prove Lieb-Thirring inequalities for Schr\"odinger operators with a homogeneous magnetic field in two and three space dimensions. The inequalities bound sums of eigenvalues by a semi-classical approximation which depends on the strength…

Spectral Theory · Mathematics 2015-05-27 Rupert L. Frank , Rikard Olofsson

We prove a Payne-Weinberger type inequality for the $p$-Laplacian Neumann eigenvalues ($p\ge 2$). The inequality provides the sharp upper bound on convex domains, in terms of the diameter alone, of the best constants in Poincar\'e…

Analysis of PDEs · Mathematics 2011-10-14 L. Esposito , C. Nitsch , C. Trombetti

We consider the Laplacian eigenvalues for smooth planar domains with strongly attractive Robin conditions imposed on a part of the boundary and Neumann condition on the remaining boundary. The asymptotics of individual eigenvalues is…

Spectral Theory · Mathematics 2024-06-13 Konstantin Pankrashkin

In this paper we prove an optimal upper bound for the first eigenvalue of a Robin-Neumann boundary value problem for the p-Laplacian operator in domains with convex holes. An analogous estimate is obtained for the corresponding torsional…

Analysis of PDEs · Mathematics 2024-10-08 Francesco Della Pietra , Gianpaolo Piscitelli
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