Simple Words in Equality Sets.
Mario Lipponen, Arto K. Salomaa · 1996
It is well known that equality sets between two morphisms possess a remarkable generative capacity: an arbitrary recursively enumerable set is obtained from an equality set by certain simple operations. Interconnections between simplicity of computations and structural primitivity of words in equality sets have also been observed. The paper discusses recent work in this area, pointing out certain open problems and emphasizing new directions for research. TUCS Research Group