Duval–Reiner conjecture for simplicial-complex Laplacians

Let KK be a kk-family on vertex set V(K)V(K). Let ∂k−1\partial_{k-1} be its boundary operator, and let s=(s1≥s2≥⋯ )\mathbf{s}=(s_1\ge s_2\ge\cdots) be the nonincreasing sequence of nonzero eigenvalues of ∂k−1∂k−1∗\partial_{k-1}\partial_{k-1}^*. Let d=(d1≥d2≥⋯ )\mathbf{d}=(d_1\ge d_2\ge\cdots) be the vertex degree sequence of KK, and let d⊤\mathbf{d}^\top be its conjugate sequence. For nonincreasing sequences x\mathbf{x} and y\mathbf{y}, x≺y\mathbf{x}\prec\mathbf{y} means that their partial sums satisfy the majorization inequalities and their total sums are equal.

Duval–Reiner conjecture. The eigenvalue sequence is majorized by the conjugate vertex degree sequence:

s≺d⊤.\mathbf{s}\prec\mathbf{d}^\top.

This is proposed as a far-reaching analogue of the Grone–Merris conjecture for simplicial complexes. The supplied text does not state whether the conjecture has been proved or refuted.

References

Primary source

Yueli Han, Lu Lu and Jianfeng Wang, “On the sum of the two largest eigenvalues of the curl-curl operator on graphs”, arXiv:2606.26512 (2026).

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