On the separability of cyclotomic schemes over finite fields

Abstract

It is proved that with finitely many possible exceptions, each cyclotomic scheme over a finite field is determined up to isomorphism by the tensor of 2 2 -dimensional intersection numbers; for infinitely many schemes, this result cannot be improved. As a consequence, the Weisfeiler–Leman dimension of a Paley graph or tournament is at most  3 3 with possible exception of several small graphs.