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arXiv · 1607.03072

Perturbation theory for spectral gap edges of 2D periodic Schr\"odinger operators

Leonid Parnovski·Roman Shterenberg
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Abstract

We consider a two-dimensional periodic Schr\"odinger operator $H=-\Delta+W$ with $\Gamma$ being the lattice of periods. We investigate the structure of the edges of open gaps in the spectrum of $H$. We show that under arbitrary small perturbation $V$ periodic with respect to $N\Gamma$ where $N=N(W)$ is some integer, all edges of the gaps in the spectrum of $H+V$ which are perturbation of the gaps of $H$ become non-degenerate, i.e. are attained at finitely many points by one band function only and have non-degenerate quadratic minimum/maximum. We also discuss this problem in the discrete setting and show that changing the lattice of periods may indeed be unavoidable to achieve the non-degeneracy.

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Leonid Parnovski, Roman Shterenberg. 2016-07-11. Perturbation theory for spectral gap edges of 2D periodic Schr\"odinger operators. https://arxiv.org/abs/1607.03072

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