Circular Chromatic Number of Flower Graphs

Guo-Gane Gao1, Gena Hahn2, HulsHan Zuou3
1Département d’informatique et de recherche opérationnelle Université de Montréal 2900 Boulevard Edouard-Montpetit Montréal, Québec, Canada H3C 3J7
2Département d’informatique et de recherche opérationnelle Université de Montréal 2900 Boulevard Edouard-Montpetit Montréal, Québec, Canada
3BellSouth Applied Technology, 5515 Spalding Drive, Norcors, GA30092 USA.

Abstract

Vince asked whether for each rational \( r \) between 2 and 4 there was a planar graph of circular chromatic number \( r \). Moser and Zhu showed that the answer is yes, the first for \( 2 < r < 3 \), the second for \( 3 < r < 4 \). This paper gives another family of planar graphs with circular chromatic number between 2 and 3.