Asymptotic behavior of some factorizations of random words

Philippe Chassaing (1) , Elahe Zohoorian Azad (2)

1 IECL - Institut Élie Cartan de Lorraine
2 Damghan University of Basic Sciences

This paper considers the normalized lengths of the factors of the Lyndon decomposition of finite random words with $n$ independent letters drawn from a finite or infinite totally ordered alphabet according to a general probability distribution. We prove, firstly, that the limit law of the lengths of the smallest Lyndon factors is a variant of the stickbreaking process. Convergence of the distribution of the lengths of the longest factors to a Poisson-Dirichlet distribution follows. Secondly, we prove that the distribution of the normalized length of the standard right factor of a random $n$-letters long Lyndon word, derived from such an alphabet, converges, when $n$ is large, to: $$ \mu(dx)=p_1 \delta_{1}(dx) + (1-p_1) \mathbf{1}_{[0,1)}(x)dx, $$ in which $p_1$ denotes the probability of the smallest letter of the alphabet.

Mots clés: random word; Lyndon word; standard right factor; Lyndon factor; longest run; convergence in distribution; Poisson-Dirichlet distribution

Domaines: Probabilités [math.PR]

Philippe Chassaing, Elahe Zohoorian Azad. Asymptotic behavior of some factorizations of random words. Random Structures and Algorithms, inPress. ⟨hal-00475379v1⟩