A method of finding automorphism groups of endomorphism monoids of relational systems

For any set X and any relation \rho on X, let T(X,\rho) be the semigroup of all maps a : X → X that preserve \rho. Let S(X) be the symmetric group on X. If \rho is reflexive, the group of automorphisms of T (X, \rho) is isomorphic to N_{S(X)}(T (X, \rho)), the normalizer of T (X, \rho) in S(X), that is, the group of permutations on X that preserve T (X, \rho) under conjugation. The elements of N_{S(X)}(T (X, \rho)) have been described for the class of so-called dense relations \rho. The paper is dedicated to applications of this result. © 2006 Elsevier B.V. All rights reserved