Published online by Cambridge University Press: 15 August 2002
A morphism f is k-power-free if and only if f(w) is k-power-free whenever w is a k-power-free word.A morphism f is k-power-free up to m if and onlyif f(w) isk-power-free whenever w is a k-power-free word of length at most m.Given an integer k ≥ 2,we prove that a binary morphism is k-power-freeif and only if it is k-power-free up to k 2.This bound becomes linear for primitive morphisms:a binary primitive morphism is k-power-freeif and only if it is k-power-free up to 2k+1