Some operations preserving primitivity of words

Abstract

We investigate some operations where essentially, from a given word w, the word ww′ is constructed where w′ is a modified copy of w or a modified mirror image of w. We study whether ww′ is a primitive word provided that w is primitive. For instance, we determine all cases with an edit distance of w and w′ at most 2 such that the primitivity of w implies the primitivity of ww′. The operations are chosen in such a way that in the case of a two-letter alphabet, all primitive words of length ≤11 can be obtained from single letters.