English

Berge's Conjecture and Aharoni-Hartman-Hoffman's Conjecture for locally in-semicomplete digraphs

Combinatorics 2017-08-23 v1

Abstract

Let kk be a positive integer and let DD be a digraph. A path partition \sP\sP of DD is a set of vertex-disjoint paths which covers V(D)V(D). Its kk-norm is defined as P\sP\MinV(P),k\sum_{P \in \sP} \Min{|V(P)|, k}. A path partition is kk-optimal if its kk-norm is minimum among all path partitions of DD. A partial kk-coloring is a collection of kk disjoint stable sets. A partial kk-coloring \sC\sC is orthogonal to a path partition \sP\sP if each path P\sPP \in \sP meets min{P,k}\min\{|P|,k\} distinct sets of \sC\sC. Berge (1982) conjectured that every kk-optimal path partition of DD has a partial kk-coloring orthogonal to it. A (path) kk-pack of DD is a collection of at most kk vertex-disjoint paths in DD. Its weight is the number of vertices it covers. A kk-pack is optimal if its weight is maximum among all kk-packs of DD. A coloring of DD is a partition of V(D)V(D) into stable sets. A kk-pack \sP\sP is orthogonal to a coloring \sC\sC if each set C\sCC \in \sC meets \MinC,k\Min{|C|, k} paths of \sP\sP. Aharoni, Hartman and Hoffman (1985) conjectured that every optimal kk-pack of DD has a coloring orthogonal to it. A digraph DD is semicomplete if every pair of distinct vertices of DD is adjacent. A digraph DD is locally in-semicomplete if, for every vertex vV(D)v \in V(D), the in-neighborhood of vv induces a semicomplete digraph. Locally out-semicomplete digraphs are defined similarly. In this paper, we prove Berge's and Aharoni-Hartman-Hoffman's Conjectures for locally in/out-semicomplete digraphs.

Keywords

Cite

@article{arxiv.1708.06691,
  title  = {Berge's Conjecture and Aharoni-Hartman-Hoffman's Conjecture for locally in-semicomplete digraphs},
  author = {Maycon Sambinelli and Carla Negri Lintzmayer and Cândida Nunes da Silva and Orlando Lee},
  journal= {arXiv preprint arXiv:1708.06691},
  year   = {2017}
}