The radial tree-width conjecture for graphs excluding quasi-geodesic subdivisions of the triangle

Let GG be a connected graph. For c,kNc,k\in\mathbb{N}, a cc-quasi-geodesic (ck)(\geqslant ck)-subdivision of K3K^3 means a subdivision of the triangle whose subdivided paths are cc-quasi-geodesic and have length at least ckck. The radial tree-width of GG is the tree-width notion defined for radial decompositions.

Radial tree-width conjecture. There is a function f:NNf:\mathbb{N}\rightarrow\mathbb{N} such that, if a connected graph GG does not contain a cc-quasi-geodesic (ck)(\geqslant ck)-subdivision of K3K^3 for some c,kNc,k\in\mathbb{N}, then

radial tree-width(G)f(k).\operatorname{radial\ tree\text{-}width}(G)\leqslant f(k).

The preceding discussion explains that the subdivided-star argument does not directly produce a quasi-geodesic structural subgraph and presents this assertion as an unresolved question for trees. No resolution is given in the supplied text.

Sources & referencesView supporting material

Primary source

Sandra Albrechtsen, Reinhard Diestel, Ann-Kathrin Elm, Eva Fluck, Raphael W. Jacobs, Paul Knappe and Paul Wollan, “A structural duality for path-decompositions into parts of small radius”, arXiv:2307.08497 (2026).

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