Eight times four bialgebras of hypergraphs, cointeractions, and chromatic polynomials
Abstract
We consider the bialgebra of hypergraphs, a generalization of Schmitt's Hopf algebra of graphs, and show it has a cointeracting bialgebra. So one has a double bialgebra in the sense of L. Foissy, who recently proved there is then a unique double bialgebra morphism to the double bialgebra structure on the polynomial ring . We show the polynomial associated to a hypergraph is the hypergraph chromatic polynomial. Moreover hypergraphs occurs in quartets: there is a dual, a complement, and a dual complement hypergraph. These correspondences are involutions and give rise to three other double bialgebras, and three more chromatic polynomials. In all we give eight quartets of bialgebras which includes recent bialgebras of M. Aguiar and F. Ardila, and by L. Foissy.
Keywords
Cite
@article{arxiv.2212.03501,
title = {Eight times four bialgebras of hypergraphs, cointeractions, and chromatic polynomials},
author = {Kurusch Ebrahimi-Fard and Gunnar Fløystad},
journal= {arXiv preprint arXiv:2212.03501},
year = {2023}
}
Comments
29 pages. 1. Title is changed. Previously: "Twelve bialgebras of bialgebras, ..." 2. An inaccuracy concerning the cointeraction has been corrected. The coproduct of the bialgebra in the last section has been corrected. 3. Two more quartets of bialgebras are added. The last quartet comes from a recent extraction-contraction bialgebra introduced by L. Foissy