On Edge-Colored Saturation Problems

Michael Ferrara; Daniel Johnston; Sarah Loeb; Florian Pfender; Alex Schulte; Heather C. Smith; Eric Sullivan; Michael Tait; Casey Tompkins

arXiv · 1712.00163

On Edge-Colored Saturation Problems

Michael Ferrara·Daniel Johnston·Sarah Loeb·Florian Pfender·Alex Schulte·Heather C. Smith·Eric Sullivan·Michael Tait·Casey Tompkins

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Abstract

Let $\mathcal{C}$ be a family of edge-colored graphs. A $t$-edge colored graph $G$ is $(\mathcal{C}, t)$-saturated if $G$ does not contain any graph in $\mathcal{C}$ but the addition of any edge in any color in $[t]$ creates a copy of some graph in $\mathcal{C}$. Similarly to classical saturation functions, define $\mathrm{sat}_t(n, \mathcal{C})$ to be the minimum number of edges in a $(\mathcal{C},t)$ saturated graph. Let $\mathcal{C}_r(H)$ be the family consisting of every edge-colored copy of $H$ which uses exactly $r$ colors. In this paper we consider a variety of colored saturation problems. We determine the order of magnitude for $\mathrm{sat}_t(n, \mathcal{C}_r(K_k))$ for all $r$, showing a sharp change in behavior when $r\geq \binom{k-1}{2}+2$. A particular case of this theorem proves a conjecture of Barrus, Ferrara, Vandenbussche, and Wenger. We determine $\mathrm{sat}_t(n, \mathcal{C}_2(K_3))$ exactly and determine the extremal graphs. Additionally, we document some interesting irregularities in the colored saturation function.

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Michael Ferrara, Daniel Johnston, Sarah Loeb, Florian Pfender, Alex Schulte, Heather C. Smith, Eric Sullivan, Michael Tait, Casey Tompkins. 2017-12-01. On Edge-Colored Saturation Problems. https://arxiv.org/abs/1712.00163

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