THE SYNTACTIC GRAPH OF A SOFIC SHIFT IS INVARIANT UNDER SHIFT EQUIVALENCE
Marie-Pierre Béal, Francesca Fiorenzi, Dominique Perrin · International Journal of Algebra and Computation · 2006
We define a new invariant for shift equivalence of sofic shifts. This invariant, which we call the syntactic graph of a sofic shift, is the directed acyclic graph of characteristic groups of the non-null regular [Formula: see text]-classes of the syntactic semigroup of the shift.