Ivan Damnjanović - Vertex-transitive nut graph order-degree existence problem

dmtcs:15989 - Discrete Mathematics & Theoretical Computer Science, January 10, 2026, vol. 28:2 - https://doi.org/10.46298/dmtcs.15989
Vertex-transitive nut graph order-degree existence problemArticle

Authors: Ivan Damnjanović

    A nut graph is a nontrivial simple graph whose adjacency matrix has a simple eigenvalue zero such that the corresponding eigenvector has no zero entries. It is known that the order $n$ and degree $d$ of a vertex-transitive nut graph satisfy $4 \mid d$, $d \ge 4$, $2 \mid n$ and $n \ge d + 4$; or $d \equiv 2 \pmod 4$, $d \ge 6$, $4 \mid n$ and $n \ge d + 6$. Here, we prove that for each such $n$ and $d$, there exists a $d$-regular Cayley nut graph of order $n$. As a direct consequence, we obtain all the pairs $(n, d)$ for which there is a $d$-regular vertex-transitive (resp. Cayley) nut graph of order $n$.


    Volume: vol. 28:2
    Section: Graph Theory
    Published on: January 10, 2026
    Accepted on: December 28, 2025
    Submitted on: July 4, 2025
    Keywords: Combinatorics, Number Theory, 05C50, 05C25, 11C08, 12D05

    Publications

    Continues
    Damnjanović, I. (2024). Complete resolution of the circulant nut graph order–degree existence problem. In Ars Mathematica Contemporanea (Vols. 24, Issues 4, p. #P4.03). University of Primorska Press. 10.26493/1855-3974.3009.6df
    Damnjanović, I. (2025). A note on Cayley nut graphs whose degree is divisible by four. In The Art of Discrete and Applied Mathematics. University of Primorska Press. 10.26493/2590-9770.1662.4e9