H-free extension of Brouwer's Laplacian eigenvalue-sum conjecture

Less than 1 year old · traced to

Let k≥1k\ge 1, let HH be a graph, and let ex⁡(n;H)\operatorname{ex}(n;H) denote the maximum number of edges in an nn-vertex HH-free graph. For a graph G=(V,E)G=(V,E), define

ε⁡k(G)=∑i=1kλi(L(G))−∣E∣.\operatorname{\varepsilon}_k(G)=\sum_{i=1}^k\lambda_i(L(G))-|E|.

H-free Brouwer conjecture. For every HH-free graph G=(V,E)G=(V,E) with ∣V∣≥k|V|\ge k,

ε⁡k(G)≤ex⁡(k+1;H).\operatorname{\varepsilon}_k(G)\le \operatorname{ex}(k+1;H).

The paper notes that the proposed bound is sharp, using an (k+1)(k+1)-vertex extremal HH-free graph together with isolated vertices. The supplied status does not indicate whether the conjecture is resolved.

References

Primary source

Alan Lew, “An approximate version of Brouwer's Laplacian conjecture”, arXiv:2601.17575 (2026).

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.