In this paper we discuss the application of the Saxon–Hutner theorem and its converse theorem in one-dimensional binary disordered lattices to the one-dimensional binary quasiperiodic lattices. We first summarize some basic theorems in one-dimensional periodic lattices. We discuss how the bulk and edge states are treated in the transfer matrix method. Second, we review the Saxon–Hutner theorem and prove the converse theorem, using the so-called Fricke identities. Third, we present an alternative approach for a rigorous proof of the existence of a Cantor-set spectrum in the Fibonacci lattice and in the related binary quasiperiodic lattices by means of the theorems together with their trace map with the invariant I. We obtain that if I > 0, then the spectrum is always a Cantor set, which was first proved for the Fibonacci lattice by Sütö and generalized for other quasiperiodic lattices by Bellissard, Iochum, Scopolla, and Testard. Fourth, we rigorously prove the existence of extended states in the spectrum of a class of binary quasiperiodic lattices first studied by Kolář and Ali. Fifth, we discuss the so-called gap labeling theorem emphasized by Bellissard and the classic argument of Kohn and Thouless for localized states in a one-dimensional disordered lattice in terms of the language of the transfer matrix method.
(4) symmetry of the transfer matrix for the one-dimensional Hubbard model