PRIMITIVE MORPHISMS

A word is called primitive if it cannot be expressed as the power of a nother word. Morphisms preserving primitive words are investigated. Si milarly to the word case, each square-free morphism is a primitive mor phism but the converse does not hold. A precise characterization of pr imitive morphisms is provided in terms of purl codes. An easily testab le characterization is riven for uniform morphisms over the binary alp habet. (C) 1997 Elsevier Science B.V.