The bipartite MaxLA proportion conjecture for free trees

From papers

Let nn be the number of vertices, let Tn\mathcal{T}_n be the set of all free nn-vertex trees, and let Mn\mathcal{M}_n be the set of those trees for which a maximal bipartite arrangement is also a maximum arrangement. Define

propbip(n)=MnTn.\operatorname{propbip}(n)=\frac{|\mathcal{M}_n|}{|\mathcal{T}_n|}.

Strong bipartition conjecture. The limit exists and is a positive constant:

limnpropbip(n)=c,\lim_{n\to\infty}\operatorname{propbip}(n)=c,

with statistical analyses suggesting c0.5c\approx 0.5.

The conjecture predicts that a substantial proportion of free trees remain solvable by bipartite MaxLA asymptotically, which would give a linear-time method for a large class of trees. The paper presents exhaustive computations for small orders and sampling-based evidence for larger orders, but no proof of the limiting behavior is given.

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Sources & referencesView supporting material

Primary source

Lluís Alemany-Puig, Juan Luis Esteban and Ramon Ferrer-i-Cancho, “Maximum Linear Arrangement: exact algorithms for specific classes of graphs and approximation algorithms for wide classes of graphs”, arXiv:2312.04487 (2026).

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