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

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 $χ_{ON}(G)$. 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 $χ_{ON}(G) = O(k\cdot \log^{2+ε}Δ)$, for any $ε> 0$, where $Δ$ denotes the maximum degree of $G$. Further, we show existence of claw-free ($S_3$-free) graphs that require $Ω(\log Δ)$ colors.