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arXiv · 2411.17232

On decomposition thresholds for odd-length cycles and other tripartite graphs

Darryn Bryant·Peter Dukes·Daniel Horsley·Barbara Maenhaut·Richard Montgomery
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Abstract

An (edge) decomposition of a graph $G$ is a set of subgraphs of $G$ whose edge sets partition the edge set of $G$. Here we show, for each odd $\ell \geq 5$, that any graph $G$ of sufficiently large order $n$ with minimum degree at least $(\frac{1}{2}+\frac{1}{2\ell-4}+o(1))n$ has a decomposition into $\ell$-cycles if and only if $\ell$ divides $|E(G)|$ and each vertex of $G$ has even degree. This threshold cannot be improved beyond $\frac{1}{2}+\frac{1}{2\ell-2}$. It was previously shown that the thresholds approach $\frac{1}{2}$ as $\ell$ becomes large, but our thresholds do so significantly more rapidly. Our methods can be applied to tripartite graphs more generally and we also obtain some bounds for decomposition thresholds of other tripartite graphs.

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Darryn Bryant, Peter Dukes, Daniel Horsley, Barbara Maenhaut, Richard Montgomery. 2024-11-26. On decomposition thresholds for odd-length cycles and other tripartite graphs. https://doi.org/10.1016/j.jctb.2026.06.005

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