(Throughout this paper embeddings and substructures will be understood in the usual model theoretic sense (see, e.g., Hodges [Ho]); e.g., for graphs embeddings are induced embeddings, i.e.,â€¦ (More)

An important problem in topological dynamics is the calculation of the universal minimal flow of a topological group. When the universal minimal flow is one point, we say that the group is extremelyâ€¦ (More)

We consider S, the class of Â…nite semilattices; T , the class of Â…nite treeable semilattices; and Tm, the subclass of T which contains trees with branching bounded by m. We prove that ES, the classâ€¦ (More)

We consider F , the class of Â…nite unary functions, i.e. the class of pairs of the form (A; f) where A is a Â…nite set and f is an unary function on A. We also consider two subclasses of F : B and Fkâ€¦ (More)

Let K be a class of Â…nite relational structures. Let Kn be the class obtained by adding labeled partition, in at most n many parts, to structures in K. Let EK be the class obtained by addingâ€¦ (More)

We study the automorphism groups of countable homogeneous directed graphs (and some additional homogeneous structures) from the point of view of topological dynamics. We determine precisely which ofâ€¦ (More)