Bethe-Sommerfeld Conjecture and absolutely continuous spectrum of multi-dimensional quasi-periodic Schrödinger operators

Abstract

We consider Schrödinger operators $H=-\Delta+V(\mathbf{x)}$ in $\mathbb{R}^d$, $d\ge 2$, with quasi periodic potentials $V(\mathbf{x})$. We prove that the absolutely continuous spectrum of a generic $H$ contains a semi-axis $[\lambda_*,+\infty)$. We also construct a family of eigenfunctions of the absolutely continuous spectrum; these eigenfunctions are small perturbations of the exponentials. The proof is based on a version of the multi-scale analysis in the momentum space with several new ideas introduced along the way.

Authors

Yu. Karpeshina

Department of Mathematics, The University of Alabama at Birmingham, Birmingham, AL, USA

L. Parnovski

Department of Mathematics, University College London, Gower Street, London, UK

R. Shterenberg

Department of Mathematics, The University of Alabama at Birmingham, Birmingham, AL, USA