Characterizing intersection classes of graphs

Abstract A graph is an intersection graph if it is possible to assign sets to its vertices so that adjacency corresponds exactly to nonempty intersection. If the sets assigned to vertices must belong to a pre-specified family, the resulting class of all possible intersection graphs is called an intersection class. We characterize intersection classes. The main result is generalized for classes in which the assignment of sets to vertices must be one-to-one, as well as for classes of simplicial complexes arising as nerves of sets from a pre-specified family.