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arXiv · 2308.15406

On the existence of small strictly Neumaier graphs

Aida Abiad·Maarten De Boeck·Sjanne Zeijlemaker
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Abstract

A Neumaier graph is a non-complete edge-regular graph containing a regular clique. In this work, we prove several results on the existence of small strictly Neumaier graphs. In particular, we present a theoretical proof of the uniqueness of the smallest strictly Neumaier graph with parameters $(16,9,4;2,4)$, we establish the existence of a strictly Neumaier graph with parameters $(25,12,5;2,5)$, and we disprove the existence of strictly Neumaier graphs with parameters $(25,16,9;3,5)$, $(28,18,11;4,7)$, $(33,24,17;6,9)$, $(35,22,12;3,5)$ and $(55,34,18;3,5)$. Our proofs use combinatorial techniques and a novel application of integer programming methods.

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Aida Abiad, Maarten De Boeck, Sjanne Zeijlemaker. 2024-03-04. On the existence of small strictly Neumaier graphs. https://arxiv.org/abs/2308.15406

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