The range conjecture for balancing probabilities in linear extensions

Let PP be a finite poset. For x∈Px\in P, let Π(x)={y:y≁x}\Pi(x)=\{y:y\not\sim x\} and define the range parameter

π(P)=max⁡x∈P∣Π(x)∣.\pi(P)=\max_{x\in P}|\Pi(x)|.

For distinct x,y∈Px,y\in P, let δxy=min⁡{P(x≺y),P(y≺x)}\delta_{xy}=\min\{\mathbb{P}(x\prec y),\mathbb{P}(y\prec x)\}, and set

δ(P)=max⁡x≠yδxy,\delta(P)=\max_{x\ne y}\delta_{xy},

where probabilities are taken over uniformly random linear extensions. The range conjecture. If π(P)→∞\pi(P)\to\infty, then δ(P)→1/2\delta(P)\to 1/2. This is presented as an old conjecture of the second author and as a strengthening of the width-based Kahn–Saks conjecture. The supplied text does not state that it has been resolved.

References

Primary source

Max Aires and Jeff Kahn, “Variance vs. range for linear extensions, and balancing extensions in posets of bounded width”, arXiv:2510.26134 (2025).

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