Cantorval spectrum conjecture for a two-dimensional quasicrystal Schrödinger operator

Let γ=512\gamma=\frac{\sqrt{5}-1}{2} and, for j{1,2}j\in\{1,2\} and kZk\in\mathbb{Z}, define

sjλj(k)=λjχ[1γ,1)({kγ}).s_j^{\lambda_j}(k)=\lambda_j\chi_{[1-\gamma,1)}(\{k\gamma\}).

Set V(m,n)=s1λ1(m)+s2λ2(n)V(m,n)=s_1^{\lambda_1}(m)+s_2^{\lambda_2}(n) and let HH on l2(Z2)l^2(\mathbb{Z}^2) be given by

[Hψ](m,n)=ψ(m+1,n)+ψ(m1,n)+ψ(m,n+1)+ψ(m,n1)+V(m,n)ψ(m,n).[H\psi](m,n)=\psi(m+1,n)+\psi(m-1,n)+\psi(m,n+1)+\psi(m,n-1)+V(m,n)\psi(m,n).

Cantorval spectrum conjecture. There exist values of λ1\lambda_1 and λ2\lambda_2 such that the spectrum σ(H)\sigma(H) is a Cantorval; that is, the spectrum is the closure of its interior and no connected component is isolated.

The conjecture concerns the expected structure of the spectrum for a separable two-dimensional quasicrystal potential. The source gives no resolution status.

Sources & referencesView supporting material

Primary source

Faustin Adiceam, “Open Problems and Conjectures related to the Theory of Mathematical Quasicrystals”, arXiv:1604.06280 (2016).

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