English

Homomorphisms of planar $(m, n)$-colored-mixed graphs to planar targets

Combinatorics 2020-09-01 v1

Abstract

An (m,n)(m, n)-colored-mixed graph G=(V,A1,A2,,Am,E1,E2,,En)G=(V, A_1, A_2,\cdots, A_m, E_1, E_2,\cdots, E_n) is a graph having mm colors of arcs and nn colors of edges. We do not allow two arcs or edges to have the same endpoints. A homomorphism from an (m,n)(m,n)-colored-mixed graph GG to another (m,n)(m, n)-colored-mixed graph HH is a morphism φ:V(G)V(H)\varphi:V(G)\rightarrow V(H) such that each edge (resp. arc) of GG is mapped to an edge (resp. arc) of HH of the same color (and orientation). An (m,n)(m,n)-colored-mixed graph TT is said to be Pg(m,n)P_g^{(m, n)}-universal if every graph in Pg(m,n)P_g^{(m, n)} (the planar (m,n)(m, n)-colored-mixed graphs with girth at least gg) admits a homomorphism to TT. We show that planar Pg(m,n)P_g^{(m, n)}-universal graphs do not exist for 2m+n32m+n\ge3 (and any value of gg) and find a minimal (in the number vertices) planar Pg(m,n)P_g^{(m, n)}-universal graphs in the other cases.

Keywords

Cite

@article{arxiv.2008.13747,
  title  = {Homomorphisms of planar $(m, n)$-colored-mixed graphs to planar targets},
  author = {Fabien Jacques and Pascal Ochem},
  journal= {arXiv preprint arXiv:2008.13747},
  year   = {2020}
}