Characterisation of wild auxiliary arcs between vertices
Characterisation of wild auxiliary arcs between vertices
Let be a graph and let and be distinct vertices of . Write for the partially ordered set of oriented vertex separators of , let be the infinite binary tree, and let map each binary sequence to its naturally corresponding value in the unit interval. An auxiliary arc from to is called wild when it has the wildness property defined in the paper, and % \mathrel{\vcenter{\offinterlineskip \text{\sim}\vskip-.35ex\text{\sim}\vskip-.35ex\text{\sim}}} and denote the paper's auxiliary equivalence relations. Wild-arc characterisation conjecture. For every graph and every two distinct vertices and of , the following are equivalent: (1) and every auxiliary arc from to is wild; (2) there \exists a countable \subset of such that: (a) every satisfies and ; (b) the \partial ordering of induces the ordering of the rationals on ; and (c) there \exists a bijection satisfying if and only if . If maps each vertex of to the vertex separator of , is the level containing , and is the set of all vertices in the first levels of other than , then for every and every auxiliary arc from to , the set meets ; or (3) x\not% \mathrel{\vcenter{\offinterlineskip \text{\sim}\vskip-.35ex\text{\sim}\vskip-.35ex\text{\sim}}} y.
The conjecture seeks a structural characterisation of when auxiliary arcs are wild, using a countable rationally ordered family of separators arranged like the infinite binary tree. The supplied passage raises this as an outlook question and gives no evidence of resolution, so its status is open.
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Sources & referencesView supporting material
Primary source
Jan Kurkofka, “On the tangle compactification of infinite graphs”, arXiv:1908.10212 (2019).
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