Abstract
We discuss a rotation number α(λ) for second order finite difference operators. Ifk(λ) denotes the integrated density of states, thenk(λ)=2α(λ). For almost periodic operators,k(λ) is proved to lie in the frequency-module whenever λ is outside the spectrum; this yields a labelling of the gaps of the spectrum.
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Communicated by B. Simon
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Delyon, F., Souillard, B. The rotation number for finite difference operators and its properties. Commun.Math. Phys. 89, 415–426 (1983). https://doi.org/10.1007/BF01214663
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DOI: https://doi.org/10.1007/BF01214663