Complete bipartite factorisations by complete bipartite graphs

AbstractWe study complete Kp,q-factorisations of Km,n. Simple necessary conditions are found and we conjecture that these conditions are also sufficient. A general construction is given to find infinite families of factorisations proving the conjecture in many cases. The conjecture is proved for Kl,q-factorisations of Kn,n except for q = 4k + 1. The conjecture is also proved for a further family of Kl,3-factorisations

Star-factorization of symmetric complete bipartite multi-digraphs

AbstractWe show that a necessary and sufficient condition for the existence of an Sk-factorization of the symmetric complete bipartite multi-digraph λKm,n∗ is m=n≡0(modk(k−1)/d), where d=(λ,k−1)

Cycle-factorization of symmetric complete multipartite digraphs

AbstractFirst, we show that a necessary and sufficient condition for the existence of a C3-factorization of the symmetric tripartite digraph Kn1,n2,n3∗, is n1 = n2 = n3. Next, we show that a necessary and sufficient condition for the existence of a C̄2k-factorization of the symmetric complete multipartite digraph Kn1, n2,…,nm is n1 = n2 = … = nm = 0 (mod k) for even m and n1 = n2 = … = ≡ 0 (mod 2k) for odd m