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The magnetic Laplacian on a planar domain under a strong constant magnetic field has eigenvalues close to the Landau levels. We study the case when the domain is a disc and the spectrum consists of branches of eigenvalues of one dimensional…

Spectral Theory · Mathematics 2024-07-17 Ayman Kachmar , Germán Miranda

We give inequalities relating the eigenvalues of the adjacency matrix and the Laplacian of a graph, and its minimum and maximum degrees. The results are applied to derive new conditions for quasi-randomness of graphs.

Combinatorics · Mathematics 2007-05-23 Vladimir Nikiforov

The Laplacian matrix of a simple graph is the difference of the diagonal matrix of vertex degree and the (0,1) adjacency matrix. In the past decades, the Laplacian spectrum has received much more and more attention, since it has been…

Combinatorics · Mathematics 2013-10-31 Xiao-Dong Zhang

Courant theorem provides an upper bound for the number of nodal domains of eigenfunctions of a wide class of Laplacian-type operators. In particular, it holds for generic eigenfunctions of quantum graph. The theorem stipulates that, after…

Mathematical Physics · Physics 2013-03-06 Ram Band , Gregory Berkolaiko , Hillel Raz , Uzy Smilansky

Hypergraphs extend traditional graphs by enabling the representation of N-ary relationships through higher-order edges. Akin to a common approach of deriving graph Laplacians, we define function spaces and corresponding symmetric products…

Differential Geometry · Mathematics 2026-03-27 Jo Andersson Stokke , Ronny Bergmann , Martin Hanik , Christoph von Tycowicz

We study the variation of the Neumann eigenvalues of the $p$-Laplace operator under quasiconformal perturbations of space domains. This study allows to obtain lower estimates of the Neumann eigenvalues in fractal type domains. The suggested…

Analysis of PDEs · Mathematics 2017-08-02 V. Gol'dshtein , R. Hurri-Syrjänen , A. Ukhlov

This article deals with the spectral analysis of the semiclassical Neumann magnetic Laplacian on a smooth bounded domain in dimension three. When the magnetic field is constant and in the semiclassical limit, we establish a four-term…

Spectral Theory · Mathematics 2022-03-14 Frédéric Hérau , Nicolas Raymond

We introduce an analogue of Payne's nodal line conjecture, which asserts that the nodal (zero) set of any eigenfunction associated with the second eigenvalue of the Dirichlet Laplacian on a bounded planar domain should reach the boundary of…

Analysis of PDEs · Mathematics 2017-07-03 J. B. Kennedy

In this paper we consider the problem of prescribing the nodal set of low-energy eigenfunctions of the Laplacian. Our main result is that, given any separating closed hypersurface \Sigma in a compact n-manifold M, there is a Riemannian…

Differential Geometry · Mathematics 2014-04-04 Alberto Enciso , Daniel Peralta-Salas

We establish a connection between the stability of an eigenvalue under a magnetic perturbation and the number of zeros of the corresponding eigenfunction. Namely, we consider an eigenfunction of discrete Laplacian on a graph and count the…

Mathematical Physics · Physics 2013-11-21 Gregory Berkolaiko

We prove estimates for eigenfunctions on a manifold equipped with a smooth metric. We use these estimates in order estimate the size of their nodal sets.

Analysis of PDEs · Mathematics 2013-10-30 Demetrios A. Pliakis

Consider an eigenvector of the adjacency matrix of a G(n, p) graph. A nodal domain is a connected component of the set of vertices where this eigenvector has a constant sign. It is known that with high probability, there are exactly two…

Probability · Mathematics 2020-01-22 Han Huang , Mark Rudelson

We consider a Laplace eigenfunction $\varphi_\lambda$ on a smooth closed Riemannian manifold, that is, satisfying $-\Delta \varphi_\lambda = \lambda \varphi_\lambda$. We introduce several observations about the geometry of its vanishing…

Analysis of PDEs · Mathematics 2017-07-18 Bogdan Georgiev , Mayukh Mukherjee

We expand upon a graph theoretic set of uncertainty principles with tight bounds for difference estimators acting simultaneously in the graph domain and the frequency domain. We show that the eigenfunctions of a modified graph Laplacian and…

Classical Analysis and ODEs · Mathematics 2016-03-08 Paul J. Koprowski

We introduce and study Laplacians on a finite metric graph endowed with generalized densities, that is, measures of finite mass. One important motivation is that this setting provides a common framework for several interesting classes of…

Spectral Theory · Mathematics 2025-12-24 Kiyan Naderi , Noema Nicolussi

In this note we elaborate on some notions of surface area for discrete graphs which are closely related to the inverse degree. These notions then naturally lead to associated connectivity measures of graphs and to the definition of a…

Combinatorics · Mathematics 2026-03-09 Patrizio Bifulco , Joachim Kerner

An eigenfunction of the Laplacian on a metric (quantum) graph has an excess number of zeros due to the graph's non-trivial topology. This number, called the nodal surplus, is an integer between 0 and the graph's first Betti number $\beta$.…

Mathematical Physics · Physics 2022-07-13 Lior Alon , Ram Band , Gregory Berkolaiko

Determining and analyzing the spectra of graphs is an important and exciting research topic in theoretical computer science. The eigenvalues of the normalized Laplacian of a graph provide information on its structural properties and also on…

Combinatorics · Mathematics 2016-05-20 Pinchen Xie , Zhongzhi Zhang , Francesc Comellas

In this partly expository paper we discuss and describe some of our old and recent results on partial orders on the set (m,n)-graphs (i.e. graphs with n vertices and m edges) and some operations on graphs that are monotone with respect to…

Combinatorics · Mathematics 2013-12-24 Alexander Kelmans

Let G be a finite connected simple graph. We define the moduli space of conformal structures on G. We propose a definition of conformally covariant operators on graphs, motivated by [25]. We provide examples of conformally covariant…

Combinatorics · Mathematics 2014-10-07 Dmitry Jakobson , Thomas Ng , Matthew Stevenson , Mashbat Suzuki