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Farley–Sabalka’s Morse-Theory Model and the Higher Topological Complexity of Ordered Configuration Spaces on Trees

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Abstract

Using the ordered analogue of Farley–Sabalka’s discrete gradient field on the configuration space of a graph, we unravel a levelwise behavior of the generators of the pure braid group on a tree. This allows us to generalize Farber’s equivariant description of the homotopy type of the configuration space on a tree on two particles. The results are applied to the calculation of all the higher topological complexities of ordered configuration spaces on trees on any number of particles.

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Notes

  1. All cohomology groups in this paper are taken with \({\mathbb {Z}}\)-coefficients.

  2. It suffices to totally order the non-deleted edges adjacent to v.

  3. See [9], particularly Theorem 4.2, for the \({\mathscr {S}}_n\)-equivariant ingredient in the third item of Corollary 3.5.

  4. The spliced graph G(3, T) has vertices given by the six permutations ijk, and edges given by all the edges (with the indicated repetitions) shown in Figs. 2 and 3.

  5. Here and below, piling up is done according to (9), without leaving empty spots in the tree (as in (11)).

  6. Stacks like these are uniquely determined, as the tree has been assumed to be n-sufficiently subdivided.

  7. In this kind of expressions we extend, in the obvious way, the abuse of terminology in (10).

  8. An \(a_0\)-local T-branch is a sequence of edges \((a_0,b), (b,c), (c,d),\ldots \) (it implies \(a_0<b<c<d<\ldots \)).

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Correspondence to Jesús González.

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Aguilar-Guzmán, J., González, J. & Hoekstra-Mendoza, T. Farley–Sabalka’s Morse-Theory Model and the Higher Topological Complexity of Ordered Configuration Spaces on Trees. Discrete Comput Geom 67, 258–286 (2022). https://doi.org/10.1007/s00454-021-00306-3

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