Mourre estimates for compatible Laplacians on complete manifolds with corners of codimension 2

TL;DR

This paper applies Mourre theory to compatible Laplacians on manifolds with corners of codimension 2, establishing spectral properties such as absence of singular spectrum and finite multiplicity of eigenvalues.

Contribution

It extends Mourre estimates to manifolds with corners of codimension 2, providing a comprehensive framework and potential for generalizations to higher codimension corners.

Findings

Proves absence of singular spectrum for the Laplacians.

Shows non-threshold eigenvalues have finite multiplicity.

Eigenvalues can only accumulate at thresholds or infinity.

Abstract

We apply Mourre theory to compatible Laplacians on manifolds with corners of codimension 2 in order to prove absence of singular spectrum, that non-threshold eigenvalues have finite multiplicity and could accumulate only at thresholds or infinity. It turns out that we need Mourre estimates on manifolds with cylindrical ends where the results are both expected and consequences of more general theorems. In any case we also provide a description, interesting in its own, of Mourre theory in such context that makes our text complete and suggests generalizations to higher order codimension corners. We use theorems of functional analysis that are suitable for these geometric applications.