Opening gaps in the spectrum of strictly ergodic Schrödinger operators. (English) Zbl 1263.37007
Authors’ abstract: We consider Schrödinger operators with dynamically defined potentials arising from continuous sampling along orbits of strictly ergodic transformations. The gap labeling theorem states that the possible gaps in the spectrum can be canonically labeled by an at most countable set defined purely in terms of the dynamics. Which labels actually appear depends on the choice of the sampling function; the missing labels are said to correspond to collapsed gaps. Here we show that for any collapsed gap, the sampling function may be continuously deformed so that the gap immediately opens. As a corollary, we conclude that for generic sampling functions, all gaps are open. The proof is based on the analysis of continuous \(\mathrm{SL}(2,\mathbb R)\) cocycles, for which we obtain dynamical results of independent interest.
MSC:
| 37A25 | Ergodicity, mixing, rates of mixing |
| 37A20 | Algebraic ergodic theory, cocycles, orbit equivalence, ergodic equivalence relations |
| 47A35 | Ergodic theory of linear operators |
| 47A10 | Spectrum, resolvent |
| 47B37 | Linear operators on special spaces (weighted shifts, operators on sequence spaces, etc.) |
| 35J10 | Schrödinger operator, Schrödinger equation |
| 81Q05 | Closed and approximate solutions to the Schrödinger, Dirac, Klein-Gordon and other equations of quantum mechanics |
| 37K60 | Lattice dynamics; integrable lattice equations |
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