The range conjecture for balancing probabilities in linear extensions

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

π(P)=maxxPΠ(x).\pi(P)=\max_{x\in P}|\Pi(x)|.

For distinct x,yPx,y\in P, let δxy=min{P(xy),P(yx)}\delta_{xy}=\min\{\mathbb{P}(x\prec y),\mathbb{P}(y\prec x)\}, and set

δ(P)=maxxyδxy,\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.

Sources & referencesView supporting material

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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