On a Generalization of Standard Episturmian Morphisms

In a recent paper with L. Q. Zamboni the authors introduced the class of θ-episturmian words, where θ is an involutory antimorphism of the free monoid A∗. In this paper, we introduce and study θcharacteristic morphisms, that is, morphisms which map standard episturmian words into standard θ-episturmian words. They are a natural extension of standard episturmian morphisms. The main result of the paper is a characterization of these morphisms when they are injective.