Alon's star-forest extremal-graph conjecture

Let HH be a star forest, meaning a vertex-disjoint union of stars. For a graph GG, let N(G,H)N(G,H) be the number of subgraphs of GG isomorphic to HH, and let

N(m,H)=max{N(G,H):e(G)=m}.N(m,H)=\max\{N(G,H):e(G)=m\}.

Alon's star-forest extremal-graph conjecture. For every integer m>0m>0, or at least for all sufficiently large mm, there exists a star forest GmG_m with e(Gm)=me(G_m)=m such that

N(m,H)=N(Gm,H).N(m,H)=N(G_m,H).

The conjecture describes the form of an extremal graph for counting a fixed star forest with a prescribed number of edges. The supplied text gives no resolution evidence, so whether the assertion holds for every mm or only eventually remains open.

Sources & referencesView supporting material

Primary source

Peiru Kuang, Shuang Sun, Yan Wang and Jiasheng Zeng, “Proofs of Two Conjectures of Alon on Subgraph Counts”, arXiv:2606.18321 (2026).

Additional references

2 papers in this index state this conjecture (2016–2026). The statement above is taken from the most recent of them; the others are arXiv:1601.01211.

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