We extend in this work the Jitomirskaya-Last inequality and Last-Simoncriterion for the absolutely continuous spectral component of a half-line Schr\"odinger operator to the special class of matrix-valued Jacobi operators $H:l^2(\mathbb{ Z},\mathbb{ C})\rightarrow l^2(\mathbb{ Z},\mathbb{ C})$ given by the law $[H \textbf{ u}]_{ n} := D_{ n - 1} \textbf{ u}_{ n - 1} + D_{ n} \textbf{ u}_{ n + 1} + V_{ n} \textbf{ u}_{ n}$, where $(D_n)_n$ and $(V_n)_n$ are bilateral sequences of $l\times l$ self-adjoint matrices such that $0<\inf_{ n\in\mathbb{ Z}}s_l[D_n]\le\sup_{ n\in\mathbb{ Z}}s_1[D_n]<\infty$ (here, $s_k[A]$ stands for the $k$-th singular value of $A$). Moreover, we also show that the absolutely continuous components of even multiplicity of minimal dynamically defined matrix-valued Jacobi operators are constant, extending another result from Last-Simon originally proven for scalar Schr\"odinger operators.
Categories: math.SP math-ph math.MP