Containment conjecture for spectra of universal covers and limiting eigenvalue supports

Let J0J_0 be a Jacobi matrix on a finite connected graph G0\mathcal G_0. Let Gn\mathcal{G}_n be a sequence of finite connected covers of G0\mathcal G_0 such that V(Gn)|V(\mathcal{G}_n)| \to \infty, and let JnJ_n be the lift of J0J_0 to Gn\mathcal{G}_n. Let JTJ_T be the lift of JJ to the universal cover TT. Let νn\nu_n be the normalized eigenvalue counting measure of JnJ_n and assume that the weak limit ν=limnνn\nu_\infty=\lim_{n \to \infty}\nu_n exists.

Containment conjecture.

σ(JT)suppν.\sigma(J_T)\subseteq \operatorname{supp}\nu_\infty.

This conjecture asserts that, for connected finite covers, the spectrum of the lifted Jacobi matrix on the universal cover is contained in the support of every limiting eigenvalue counting measure. It proposes that disconnected covers are the only obstruction to such containment; the statement remains open in the supplied source.

Sources & referencesView supporting material

Primary source

Jonathan Breuer and Eyal Seelig, “Spectral Gaps for Jacobi Matrices on Graphs”, arXiv:2402.07202 (2024).

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