Conflict-Free Coloring of Star-Free Graphs on Open Neighborhoods

TL;DR

This paper investigates conflict-free coloring of star-free graphs on open neighborhoods, establishing bounds on the number of colors needed and demonstrating the existence of graphs requiring logarithmic colors.

Contribution

It provides upper bounds on the conflict-free chromatic number for S_k-free graphs and shows that some claw-free graphs need logarithmic colors.

Findings

h_{ON}(G) = O(k \, \log^{2+\epsilon} \Delta) for S_k-free graphs

Existence of claw-free graphs requiring ig(\, \log \Delta\big) colors

Bounds depend on maximum degree and forbidden star size

Abstract

Given a graph, the conflict-free coloring problem on open neighborhoods (CFON) asks to color the vertices of the graph so that all the vertices have a uniquely colored vertex in its open neighborhood. The smallest number of colors required for such a coloring is called the conflict-free chromatic number and denoted $\chi_{ON}(G)$. In this note, we study this problem on $S_k$-free graphs where $S_k$ is a star on $k+1$ vertices. When $G$ is $S_k$-free, we show that $\chi_{ON}(G) = O(k\cdot \log^{2+\epsilon}\Delta)$, for any $\epsilon > 0$, where $\Delta$ denotes the maximum degree of $G$. Further, we show existence of claw-free ($S_3$-free) graphs that require $\Omega(\log \Delta)$ colors.