A characterization of symmetric cones by an order-reversing property of the pseudoinverse maps

Abstract. When a homogeneous convex cone is given, a natural partial order is introduced in the ambient vector space. We shall show that a homogeneous convex cone is a symmetric cone if and only if Vinberg’s ∗-map and its inverse reverse the order. Actually our theorem is formulated in terms of the family of pseudoinverse maps including the ∗-map, and states that the above order-reversing property is typical of the ∗-map of a symmetric cone which coincides with the inverse map of the Jordan algebra associated with the symmetric cone. 1