English

Properties of chromatic polynomials of hypergraphs not held for chromatic polynomials of graphs

Combinatorics 2017-04-24 v3

Abstract

In this paper, we present some properties on chromatic polynomials of hypergraphs which do not hold for chromatic polynomials of graphs. We first show that chromatic polynomials of hypergraphs have all integers as their zeros and contain dense real zeros in the set of real numbers. We then prove that for any multigraph G=(V,E)G=(V,E), the number of totally cyclic orientations of GG is equal to the value of P(H,1)|P(H,-1)|, where P(H,λ)P(H,\lambda) is the chromatic polynomial of a hypergraph HH which is constructed from GG. Finally we show that the multiplicity of root "00" of P(H,λ)P(H,\lambda) may be at least 22 for some connected hypergraphs HH, and the multiplicity of root "11" of P(H,λ)P(H,\lambda) may be 11 for some connected and separable hypergraphs HH and may be 22 for some connected and non-separable hypergraphs HH.

Keywords

Cite

@article{arxiv.1611.04245,
  title  = {Properties of chromatic polynomials of hypergraphs not held for chromatic polynomials of graphs},
  author = {Ruixue Zhang and Fengming Dong},
  journal= {arXiv preprint arXiv:1611.04245},
  year   = {2017}
}

Comments

3 figures, 22 pages, 48 references. Accepted for publication in the European Journal of Combinatorics