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In view of several conflicting results, we reanalyze the effects of magnetic fields on the primordial nucleosynthesis. In the case the magnetic field is homogeneous over a horizon volume, we show that the main effects of the magnetic field…

Astrophysics · Physics 2008-11-26 D. Grasso , H. R. Rubinstein

We consider the magnetic Laplacian with the homogeneous magnetic field in two and three dimensions. We prove that the $(k+1)$-th magnetic Neumann eigenvalue of a bounded convex planar domain is not larger than its $k$-th magnetic Dirichlet…

Spectral Theory · Mathematics 2024-05-21 Vladimir Lotoreichik

Let $M$ be a compact $n$-dimensional Riemannian manifold with nonnegative Ricci curvature and mean convex boundary $\partial M$. Assume that the mean curvature $H$ of the boundary $\partial M$ satisfies $H \geq (n-1) k >0$ for some positive…

Differential Geometry · Mathematics 2020-01-06 Martin Li

We study the eigenvalues of the magnetic Schroedinger operator associated with a magnetic potential A and a scalar potential q, on a compact Riemannian manifold M, with Neumann boundary conditions if the boundary is not empty. We obtain…

Differential Geometry · Mathematics 2017-09-28 Bruno Colbois , Ahmad El Soufi , Said Ilias , Alessandro Savo

A cosmological neutrino sea model is used to place bounds on torsion and Lorentz violation and primordial magnetic fields. When one uses gravitational newtonian constant $G_{N}$ we obtain more stringent bounds than the ones obtained by…

General Physics · Physics 2016-11-23 Garcia de Andrade

The magnetic fields of accretion disks play an important role in studying their evolution. We may assume that its generation is connected to the dynamo mechanism, which is similar with that in the galactic disks. Here, we propose a model of…

High Energy Astrophysical Phenomena · Physics 2021-08-11 Daniela V. Boneva , Evgeny A. Mikhailov , Maria V. Pashentseva , Dmitriy D. Sokoloff

We consider the magnetic Dirichlet Laplacian with constant magnetic field on domains of finite measure. First, in the case of a disk, we prove that the eigenvalue branches with respect to the field strength behave asymptotically linear with…

Spectral Theory · Mathematics 2025-01-20 Matthias Baur , Timo Weidl

In this article, we provide a definitive well-posedness theory for the free boundary problem in incompressible magnetohyrodynamics. Despite the clear physical interest in this system and the remarkable progress in the study of the free…

Analysis of PDEs · Mathematics 2024-12-23 Mihaela Ifrim , Ben Pineau , Daniel Tataru , Mitchell A. Taylor

We consider weighted Hardy inequalities involving the distance function to the boundary of a domain in the $N$-dimensional Euclidean space with nonempty boundary. We give a lower bound for the corresponding best Hardy constant for a domain…

Analysis of PDEs · Mathematics 2023-07-06 Ujjal Das , Yehuda Pinchover

We consider the magnetic Steklov eigenvalue problem on compact Riemannian manifolds with boundary for generic magnetic potentials and establish various results concerning the spectrum. We provide equivalent characterizations of magnetic…

Differential Geometry · Mathematics 2025-01-28 Tirumala Chakradhar , Katie Gittins , Georges Habib , Norbert Peyerimhoff

When an eigenvector of a semi-bounded operator is positive, we show that a remarkably simple argument allows to obtain upper and lower bounds for its associated eigenvalue. This theorem is a substantial generalization of Barta-like…

Spectral Theory · Mathematics 2009-11-11 Amaury Mouchet

On a compact Riemannian manifold $M$ with boundary, we give an estimate for the eigenvalues $(\lambda\_k(\tau,\alpha))\_k$ of the magnetic Laplacian with the Robin boundary conditions. Here, $\tau$ is a positive number that defines the…

Differential Geometry · Mathematics 2018-01-12 Georges Habib , Ayman Kachmar

Let $\Omega \subset \mathbb{R}^2$ be a bounded convex domain in the plane and consider \begin{align*} -\Delta u &=1 \qquad \mbox{in}~\Omega \\ u &= 0 \qquad \mbox{on}~\partial \Omega. \end{align*} If $u$ assumes its maximum in $x_0 \in…

Classical Analysis and ODEs · Mathematics 2017-10-10 Stefan Steinerberger

One-particle eigenstates and eigenvalues of two-dimensional electrons in the strong magnetic field with short range impurity and impurities, cosine potential, boundary potential, and periodic array of short range potentials are obtained by…

Condensed Matter · Physics 2009-10-22 K. Ishikawa , N. Maeda , K. Tadaki

Let $\mathbb{M}$ denote a complete, simply connected Riemannian manifold with sectional curvature $K_{\mathbb{M}} \leq k$ and Ricci curvature $\text{Ric}_{\mathbb{M}} \geq (n-1)K$, where $k,K \in \mathbb{R}$. Then for a bounded domain…

Differential Geometry · Mathematics 2020-08-26 Sheela Verma

In this paper, we derive the sharp lower and upper bounds of nodal lengths of Laplacian eigenfunctions in the disc. Furthermore, we observe a geometric property of the eigenfunctions whose nodal curves maximize the nodal length.

Analysis of PDEs · Mathematics 2017-09-26 Xiaolong Han , Michael Murray , Chuong Tran

The interplay among the spectrum, geometry and magnetic field in tubular neighbourhoods of curves in Euclidean spaces is investigated in the limit when the cross section shrinks to a point. Proving a norm resolvent convergence, we derive…

Mathematical Physics · Physics 2015-06-15 David Krejcirik , Nicolas Raymond

We compute the Hofer-Zehnder capacity of magnetic disc tangent bundles over constant curvature surfaces. We use the fact that the magnetic geodesic flow is totally periodic and can be reparametrized to obtain a Hamiltonian circle action.…

Symplectic Geometry · Mathematics 2023-11-02 Johanna Bimmermann

We investigate the measure of nodal sets for Robin and Neumann eigenfunctions in the domain and on the boundary of the domain. A polynomial upper bound for the interior nodal sets is obtained for Robin eigenfunctions in the smooth domain.…

Analysis of PDEs · Mathematics 2020-04-29 Jiuyi Zhu

We study the minimization of the positive principal eigenvalue associated to a weighted Neumann problem settled in a bounded smooth domain $\Omega\subset \mathbb{R}^{N}$, within a suitable class of sign-changing weights. Denoting with $u$…

Analysis of PDEs · Mathematics 2021-11-03 Dario Mazzoleni , Benedetta Pellacci , Gianmaria Verzini