The Dry Ten Martini Problem for Sturmian Graphs

The Dry Ten Martini Problem for Sturmian Graphs

The Dry Ten Martini Problem for Sturmian Graphs

יום שני, יוני 8, 2026
  • דובר: Gilad Sofer
  • מיקום: Amado 509
Abstract:
“Are all gaps there?” - a question originally posed by Mark Kac for the Almost-Mathieu operator and later termed the Dry Ten Martini Problem by Simon - asks whether all gap labels predicted by the Gap Labelling Theorem are attained by the integrated density of states. For the Almost-Mathieu operator and for Sturmian Hamiltonians, this problem has been resolved in many regimes, with all allowed gaps shown to be open. In this talk, we introduce a geometric analogue of this problem for operators on dynamically defined graphs generated by Sturmian subshifts. Here the aperiodicity is encoded not in a potential, but in the underlying geometric structure. We compute the corresponding gap labels explicitly and show that, in contrast to the classical Sturmian Hamiltonians, not all allowed gaps are open. Moreover, the collection of attained gap labels depends on arithmetic properties of the Sturmian frequency. The missing gaps come from a geometric mechanism: the local structure of the graph produces flat bands, leading to unattained gap labels. Based on joint work with Ram Band. Advisor: Associate Prof. Ram Band
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