English

Triangle decompositions of $\lambda K_v-\lambda K_w-\lambda K_u$

Combinatorics 2019-10-09 v1

Abstract

Denote by λKv\lambda K_v the complete graph of order vv with multiplicity λ\lambda. Let λKvλKwλKu\lambda K_v-\lambda K_w-\lambda K_u be the graph obtained from λKv\lambda K_v by the removal of the edges of two vertex disjoint complete multi-subgraphs with multiplicity λ \lambda of orders w w and u u , respectively. When λ\lambda is odd, it is shown that there exists a triangle decomposition of λKvλKwλKu\lambda K_v-\lambda K_w-\lambda K_u if and only if vw+u+max{u,w}v\geq w+u+\max\{u,w\}, λ((v2)(u2)(w2))0(mod3) \lambda \left({v\choose 2}-{u\choose 2}-{w\choose 2}\right) \equiv 0 \pmod 3 and λ(vw)λ(vu)λ(v1)0(mod2)\lambda (v-w) \equiv \lambda (v-u) \equiv \lambda (v-1) \equiv 0 \pmod 2. When λ\lambda is even, it is shown that for large enough vv, the elementary necessary conditions for the existence of a triangle decomposition of λKvλKwλKu\lambda K_v-\lambda K_w-\lambda K_u are also sufficient.

Keywords

Cite

@article{arxiv.1910.03163,
  title  = {Triangle decompositions of $\lambda K_v-\lambda K_w-\lambda K_u$},
  author = {Yueting Li and Yanxun Chang and Tao Feng},
  journal= {arXiv preprint arXiv:1910.03163},
  year   = {2019}
}
R2 v1 2026-06-23T11:37:09.091Z