4 citations · 8 across the 19 of their papers we have counts for
8 papers · 1 filter
Inequalities between Dirichlet and Neumann eigenvalues on Carnot groups
Rupert L. Frank, Bernard Helffer, Ari Laptev
We show that the -th Dirichlet eigenvalue of the sub-Laplacian on an open set of a Carnot group is greater than the -st Neumann eigenvalue. This extends earlier results i…
On the magnetic Dirichlet to Neumann operator on the disk -- strong diamagnetism and strong magnetic field limit--
Helffer Bernard, Nicoleau François
Inspired by a paper by T. Chakradhar, K. Gittins, G. Habib and N. Peyerimhoff, we analyze their conjecture that the ground state energy of the magnetic Dirichlet-to-Neumann operato…
A rigorous Peierls-Onsager effective dynamics for semimetals in long-range magnetic fields
Horia D. Cornean, Bernard Helffer, Radu Purice
We consider periodic (pseudo)differential {elliptic operators of Schrödinger type} perturbed by weak magnetic fields not vanishing at infinity, and extend our previous analysis in…
Eigenvalues of the Neumann magnetic Laplacian in the unit disk
Bernard Helffer, Corentin Léna
In this paper, we study the first eigenvalue of the magnetic Laplacian with Neumann boundary conditions in the unit disk in . There is a rather complete as…
The index of sub-laplacians: beyond contact manifolds
Magnus Goffeng, Bernard Helffer
In this paper we study the following question: do sub-Laplacian type operators have non-trivial index theory on Carnot manifolds in higher degree of nilpotency? The problem relates…
Global counterexamples to uniqueness for a Calderón problem with conductivities
Thierry Daudé, Bernard Helffer, Niky Kamran +1
Let , , be a fixed smooth bounded domain, and let be a smooth conductivity in . Consider a non-zero frequency which does not belong to…
Trace formulas for the magnetic Laplacian and Dirichlet to Neumann operator -- Explicit expansions --
Bernard Helffer, François Nicoleau
Inspired by a recent paper of G. Liu and X. Tan (2023), we would like to measure how the magnetic effect appears in the heat trace formula associated with the magnetic Laplacian an…
On Courant and Pleijel theorems for sub-Riemannian Laplacians
Rupert L. Frank, Bernard Helffer
We are interested in the number of nodal domains of eigenfunctions of sub-Laplacians on sub-Riemannian manifolds. Specifically, we investigate the validity of Pleijel's theorem, wh…