Resistance, oddness and colouring defect of snarks
Abstract
Let be a bridgeless cubic graph. The \textit{resistance} of , denoted , is the minimum number of edges which can be removed from in order to render 3-edge-colourability. The \textit{oddness} of , denoted , is the minimum number of odd components in a 2-factor of . The \textit{colouring defect} of (or simply, the \textit{defect} of ), denoted , is the minimum number of edges not contained in any set of three perfect matchings of . These three parameters are regarded as measurements of uncolourability of snarks, partly because any one of these parameters equal zero if and only if is 3-edge-colourable. It is also known that and that \cite{fiol,jinsteffen}. We have shown that the ratio of oddness to resistance can be arbitrarily large for non-trivial snarks \cite{allie1}. It has also been shown that the ratio of the defect to oddness can be arbitrarily large for non-trivial snarks, although this result was only shown for graphs with oddness equal to 2 \cite{karabasetal}. In the same paper, the question was posed whether there exists non-trivial snarks for given resistance or given oddness , and arbitrarily large defect. In this paper, we prove a stronger result: For any positive integers , even , and , there exists a non-trivial snark with , and .
Cite
@article{arxiv.2407.09101,
title = {Resistance, oddness and colouring defect of snarks},
author = {Imran Allie},
journal= {arXiv preprint arXiv:2407.09101},
year = {2024}
}