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arXiv · 1305.2670

4-critical graphs on surfaces without contractible (<=4)-cycles

Zdeněk Dvořák·Bernard Lidický
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Abstract

We show that if G is a 4-critical graph embedded in a fixed surface $\Sigma$ so that every contractible cycle has length at least 5, then G can be expressed as $G=G'\cup G_1\cup G_2\cup ... \cup G_k$, where $|V(G')|$ and $k$ are bounded by a constant (depending linearly on the genus of $\Sigma$) and $G_1\ldots,G_k$ are graphs (of unbounded size) whose structure we describe exactly. The proof is computer-assisted - we use computer to enumerate all plane 4-critical graphs of girth 5 with a precolored cycle of length at most 16, that are used in the basic case of the inductive proof of the statement.

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Zdeněk Dvořák, Bernard Lidický. 2013-05-13. 4-critical graphs on surfaces without contractible (<=4)-cycles. https://doi.org/10.1137/130920952

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