English

Factorizations of regular graphs of infinite degree

Combinatorics 2021-07-20 v2

Abstract

Let H={Hi:i<α}\mathcal{H}=\{H_i: i<\alpha \} be an indexed family of graphs for some ordinal number α\alpha. H\mathcal{H}-decomposition of a graph GG is a family G={Gi:i<α}\mathcal{G}=\{G_i: i<\alpha \} of edge-disjoint subgraphs of GG such that GiG_i is isomorphic to HiH_i for every i<αi<\alpha and {E(Gi):i<α}=E(G)\bigcup\{E(G_i):i<\alpha\}=E(G). H\mathcal{H}-factorization of GG is a H\mathcal{H}-decomposition of GG such that every element of H\mathcal{H} is a spanning subgraph of GG. Let κ\kappa be an infinite cardinal. K\H{o}nig in 1936 proved that every κ\kappa-regular graph has a factorization into perfect matchings. Andersen and Thomassen using this theorem proved in 1980 that every κ\kappa-regular connected graph has a κ\kappa-regular spanning tree. We generalize both these results and establish the existence of a factorization of κ\kappa-regular graph into λ\lambda-regular subgraphs for every non-zero λκ\lambda\leq \kappa. Furthermore, we show that every κ\kappa-regular connected graph has a H\mathcal{H}-factorization for every family H\mathcal{H} of κ\kappa forests with κ\kappa components of order at most κ\kappa and without isolated vertices.

Keywords

Cite

@article{arxiv.2103.07913,
  title  = {Factorizations of regular graphs of infinite degree},
  author = {Marcin Stawiski},
  journal= {arXiv preprint arXiv:2103.07913},
  year   = {2021}
}