Episturmian morphisms constitute a powerful tool to study episturmian words. Indeed, any episturmian word can be infinitely decomposed over the set of pure episturmian morphisms. Thus, an episturmian word can be defined by one of its morphic decompositions or, equivalently, by a certain directive word. Here we characterize pairs of words directing a common episturmian word. As a consequence, we...

We study the logarithmic frequency of letters and words in morphic sequences and show that this frequency must always exist, answering a question of Allouche and Shallit.

The hypothesis of formative causation predicts that as animals of a given species learn a new pattern of behaviour, other similar animals will subsequently tend to learn the same thing more readily all over the world, as a result of a process called morphic resonance. The more that learn it, the easier it should become for others. This possibility was tested with day- old chicks using a simple ...