Flat bands of periodic graphs

M Sabri, P Youssef - Journal of Mathematical Physics, 2023 - pubs.aip.org
We study flat bands of periodic graphs in a Euclidean space. These are infinitely degenerate
eigenvalues of the corresponding adjacency matrix, with eigenvectors of compact support …

Floquet isospectrality for periodic graph operators

W Liu - Journal of Differential Equations, 2023 - Elsevier
Abstract Let Γ= q 1 Z⊕ q 2 Z⊕⋯⊕ qd Z with arbitrary positive integers ql, l= 1, 2,⋯, d. Let Δ
discrete+ V be the discrete Schrödinger operator on Z d, where Δ discrete is the discrete …

Fermi isospectrality for discrete periodic Schrödinger operators

W Liu - Communications on Pure and Applied Mathematics, 2024 - Wiley Online Library
Abstract Let Γ= q 1 Z⊕ q 2 Z⊕…⊕ qd Z Γ=q_1Z⊕q_2Z⊕...⊕q_dZ, where ql∈ Z+ q_l∈Z_+,
l= 1, 2,…, dl=1,2,...,d, are pairwise coprime. Let Δ+ V Δ+V be the discrete Schrödinger …

Quantum ergodicity for periodic graphs

T McKenzie, M Sabri - Communications in Mathematical Physics, 2023 - Springer
This article shows that for a large class of discrete periodic Schrödinger operators, most
wavefunctions resemble Bloch states. More precisely, we prove quantum ergodicity for a …

Proof of geometric Borg's Theorem in arbitrary dimensions

W Liu - arxiv preprint arxiv:2306.16412, 2023 - arxiv.org
Let $\Delta+ V $ be the discrete Schr\" odinger operator, where $\Delta $ is the discrete
Laplacian on $\mathbb {Z}^ d $ and the potential $ V:\mathbb {Z}^ d\to\mathbb {C} $ is …

Bloch varieties and quantum ergodicity for periodic graph operators

W Liu - Journal d'Analyse Mathématique, 2024 - Springer
For periodic graph operators, we establish criteria to determine the overlaps of spectral band
functions based on Bloch varieties. One criterion states that for a large family of periodic …

Critical points of discrete periodic operators

M Faust, F Sottile - Journal of Spectral Theory, 2024 - ems.press
We study the spectra of operators on periodic graphs using methods from combinatorial
algebraic geometry. Our main result is a bound on the number of complex critical points of …

Irreducibility of the Dispersion Polynomial for Periodic Graphs

M Faust, JL Garcia - SIAM Journal on Applied Algebra and Geometry, 2025 - SIAM
We use methods from algebra and discrete geometry to study the irreducibility of the
dispersion polynomial of a discrete periodic operator associated to a periodic graph after …

Algebraic Aspects of Periodic Graph Operators

SP Shipman, F Sottile - arxiv preprint arxiv:2502.03659, 2025 - arxiv.org
A periodic linear graph operator acts on states (functions) defined on the vertices of a graph
equipped with a free translation action. Fourier transform with respect to the translation …

Extrema of spectral band functions of two dimensional discrete periodic Schr\" odinger operators

M Faust, W Liu, E Luo - arxiv preprint arxiv:2501.11155, 2025 - arxiv.org
We use B\'{e} zout's theorem and Bernstein-Khovanskii-Kushnirenko theorem to analyze the
level sets of the extrema of the spectral band functions of discrete periodic Schr\" odinger …