Generalized Integer Splines on Arbitrary Graphs

Generalized integer splines on a graph G with integer edge weights are integer vertex labelings such that if two vertices share an edge in G, the vertex labels are congruent modulo the edge weight. We introduce collapsing operations that reduce any simple graph to a single vertex, carrying with it the edge weight information. This corresponds to a sequence of surjective maps between the associated spline modules, leading to an explicit construction of a Z-module basis in terms of the edge weights.