English

Monochromatic subgraphs in iterated triangulations

Combinatorics 2019-12-03 v1

Abstract

For integers n0n\ge 0, an iterated triangulation Tr(n)Tr(n) is defined recursively as follows: Tr(0)Tr(0) is the plane triangulation on three vertices and, for n1n\ge 1, Tr(n)Tr(n) is the plane triangulation obtained from the plane triangulation Tr(n1)Tr(n-1) by, for each inner face FF of Tr(n1)Tr(n-1), adding inside FF a new vertex and three edges joining this new vertex to the three vertices incident with FF. In this paper, we show that there exists a 2-edge-coloring of Tr(n)Tr(n) such that Tr(n)Tr(n) contains no monochromatic copy of the cycle CkC_k for any k5k\ge 5. As a consequence, the answer to one of two questions asked by Axenovich, Schade, Thomassen and Ueckerdt is negative. We also determine the radius two graphs HH for which there exists nn such that every 2-edge-coloring of Tr(n)Tr(n) contains a monochromatic copy of HH, extending a result of the above authors for radius two trees.

Keywords

Cite

@article{arxiv.1912.00123,
  title  = {Monochromatic subgraphs in iterated triangulations},
  author = {Jie Ma and Tianyun Tang and Xingxing Yu},
  journal= {arXiv preprint arXiv:1912.00123},
  year   = {2019}
}
R2 v1 2026-06-23T12:31:44.475Z