Preservation of absolutely continuous spectrum of periodic Jacobi operators under perturbations of square--summable variation

U. Kaluzhny, M. Shamis

We study self-adjoint bounded Jacobi operators of the form: (J ψ)(n) = a_n ψ(n + 1) + b_n ψ(n) +a_{n-1} ψ(n - 1) on ${\ell }^2(\mathbb{N})$. We assume that for some fixed q, the q-variation o…