The existence conjecture for 12-regular circulant nut graphs

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A circulant nut graph C(n,S)C(n,S) is a circulant graph on nn vertices whose adjacency matrix has nullity one and whose nullvector has no zero entries; here S={a1,a2,…,a6}S=\{a_1,a_2,\dots,a_6\} specifies the six positive circulant steps, giving degree 1212. The 12-regular circulant nut graph conjecture. For every even nn, n≥16n\ge 16, there exists a circulant nut graph C(n,{a1,a2,…,a6})C(n,\{a_1,a_2,\dots,a_6\}) of degree 1212. The conjecture extends the explicitly constructed examples for several even orders between 1616 and 3838 and asks for such a graph at every even order at least 1616.

References

Primary source

Nino Bašić, Martin Knor and Riste Škrekovski, “On 12-regular nut graphs”, arXiv:2102.04418 (2021).

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