The multi-edge Laplacian matching root integral variation conjecture

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Let GG be a connected graph, let F⊆E(Gc)F\subseteq E(G^c) be nonempty, and set H=G+FH=G+F. Let λ1(G),…,λn(G)\lambda_1(G),\dots,\lambda_n(G) denote the roots of the Laplacian matching polynomial of GG. Multi-edge LMRIV conjecture. Multi-edge Laplacian matching root integral variation does not occur for GG: there are no integers t1,…,tn∈Z≥0t_1,\dots,t_n\in\mathbb Z_{\geq 0} with t1+⋯+tn=2∣F∣t_1+\cdots+t_n=2|F| such that, as multisets,

{λ1(H),…,λn(H)}={λ1(G)+t1,…,λn(G)+tn}.\{\lambda_1(H),\dots,\lambda_n(H)\}=\{\lambda_1(G)+t_1,\dots,\lambda_n(G)+t_n\}.

The conjecture has been verified by computer for n≤9n\leq 9; it generalizes the one-edge patterns corresponding to one-place and two-place LMRIV and remains open in general.

References

Primary source

Sebastian M. Cioabă, Lele Liu and Yi Wang, “Two-place Laplacian matching root integral variations are impossible”, arXiv:2605.01760 (2026).

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