Homomorphisms of Trees into a Path

Let hom(G,H) denote the number of homomorphisms from a graph G to a graph H. In this paper we study the number of homomorphisms of trees into a path, and prove that hom(P[subscript m],P[subscript n]) ≤ hom(T[subscript m],P[subscript n]) ≤ hom(S[subscript m],P[subscript n]), where T[subscript m] is any tree on m vertices, and P[subscript m] and S[subscript m] denote the path and star on m vertices, respectively. This completes the study of extremal problems concerning the number of homomorphisms between trees started in the paper Graph Homomorphisms Between Trees [Electron. J. Combin., 21 (2014), 4.9] written by the authors of the current paper