VERTEX-PRIMITIVE HALF-TRANSITIVE GRAPHS

Given an infinite family of finite primitive groups, conditions are found which ensure that almost all the orbitals are not self-paired. If p is a prime number congruent to +/-1(mod 10), these conditions apply to the groups PSL(2, p) acting on the cosets of a subgroup isomorphic to A5. In this way, infinitely many vertex-primitive 1/2-transitive graphs which are not metacirculants are obtained.MathematicsStatistics & ProbabilitySCI(E)30ARTICLE113-1245