Lew's matching-number conjecture for Laplacian eigenvalue sums

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Let GG be a finite simple graph with nn non-isolated vertices. Let L(G)L(G) be its Laplacian matrix, let λ1(G)≥⋯≥λn(G)\lambda_1(G)\ge\cdots\ge\lambda_n(G) be the Laplacian eigenvalues, and write

sk(G)=∑i=1kλi(G).s_k(G)=\sum_{i=1}^k\lambda_i(G).

Let ν(G)\nu(G) denote the matching number of GG. Lew's matching-number conjecture. If 1≤k≤n−21\le k\le n-2, then

sk(G)≤e(G)+kν(G).s_k(G)\le e(G)+k\nu(G).

This conjecture refines parameter-dependent upper bounds for sums of the largest Laplacian eigenvalues by using the matching number. The supplied text does not state whether Lew's conjecture has been resolved.

References

Primary source

Junying Lu and Jiabao Yang, “Proofs of two conjectures on generalizations of Brouwer's Laplacian conjecture”, arXiv:2607.08452 (2026).

Additional references

2 papers in this index state this conjecture (2026). The statement above is taken from the most recent of them; the others are arXiv:2607.07118.

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