The Kahn–Saks conjecture on balance in wide posets

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Let PP be a finite poset, let w(P)w(P) denote its width, and let δ(P)\delta(P) be the maximum, over distinct x,y∈Px,y\in P, of min⁡p(x≺y),p(y≺x)\min\\{p(x\prec y),p(y\prec x)\\}. The Kahn–Saks conjecture. If the width tends to infinity, then

w(P)⟶∞⟹δ(P)⟶12.w(P)\longrightarrow\infty \quad\Longrightarrow\quad \delta(P)\longrightarrow \frac12.

The conjecture predicts asymptotically optimal balance for posets of growing width. The text identifies it as still open; it is related to several stronger-looking parameter conjectures developed later in the paper.

References

Primary source

Max Aires and Jeff Kahn, “Balancing Extensions in Posets of Large Width”, arXiv:2509.11549 (2025).

Additional references

4 papers in this index state this conjecture (2018–2025). The statement above is taken from the most recent of them; the others are arXiv:2311.02743, arXiv:2005.08390, arXiv:1811.01500.

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