A note on the A.C. spectrum of limit-periodic Jacobi matrices

Abstract

We show that limit-periodic Jacobi matrices in the weak exponential class $EC(η)$ have purely absolutely continuous spectral type when $η$ is sufficiently large, depending only on the $R$-boundedness constant. The proof first establishes homogeneity of the spectrum from the weak exponential approximation rate. A closure theorem for reflectionless Jacobi matrices then transfers reflectionlessness from the periodic approximants to the limit, and a theorem of Poltoratski and Remling rules out singular spectrum on a homogeneous set.