A relational first order structure is homogeneous if it is countable (possibly finite) and every isomorphism between finite substructures extends to an automorphism. This artic...
Abstract. A topos version of Cantor's back and forth theorem is established and used to prove that the ordered structure of the rational numbers Q, < is homogeneous in any ...
We study relational structures (especially graphs and posets) which satisfy the analogue of homogeneity but for homomorphisms rather than isomorphisms. The picture is rather diffe...