Christoffel words

Markov numbers, Christoffel words, and the uniqueness conjecture

Among their many remarkable properties, Christoffel words are known to be linked to Markov numbers, i.e., positive integer solutions to the equation $x^2+y^2+z^2=3xyz$. We express Markov numbers as coefficients of Christoffel words for a …

On Christoffel and standard words and their derivatives

We introduce and study natural derivatives for Christoffel and finite standard words, as well as for characteristic Sturmian words. These derivatives, which are realized as inverse images under suitable morphisms, preserve the aforementioned classes …

Sturmian words and the Stern sequence

Central, standard, and Christoffel words are three strongly interrelated classes of binary finite words which represent a finite counterpart to characteristic Sturmian words. A natural arithmetization of the theory is obtained by representing …

Reversible Christoffel factorizations

We define a family of natural decompositions of Sturmian words in Christoffel words, called reversible Christoffel (RC) factorizations. They arise from the observation that two Sturmian words with the same language have (almost always) …

Some characterizations of Sturmian words in terms of the lexicographic order

In this paper we present three new characterizations of Sturmian words based on the lexicographic ordering of their factors.

Christoffel words and the Calkin-Wilf tree

In this note we present some results on the Calkin-Wilf tree of irreducible fractions, giving an insight on the duality relating it to the Stern-Brocot tree, and proving noncommutative versions of known results relating labels of the Calkin Wilf …