English

Hurwitz-Ran spaces

Algebraic Topology 2023-08-01 v3 Geometric Topology

Abstract

Given a couple of subspaces YX\mathcal{Y}\subset\mathcal{X} of the complex plane C\mathbb{C} satisfying some mild conditions (a ``nice couple''), and given a PMQ-pair (Q,G)(\mathcal{Q},G), consisting of a partially multiplicative quandle (PMQ) Q\mathcal{Q} and a group GG, we introduce a ``Hurwitz-Ran'' space Hur(X,Y;Q,G)\mathrm{Hur}(\mathcal{X},\mathcal{Y};\mathcal{Q},G), containing configurations of points in XY\mathcal{X}\setminus\mathcal{Y} and in Y\mathcal{Y} with monodromies in Q\mathcal{Q} and in GG, respectively. We further introduce a notion of morphisms between nice couples, and prove that Hurwitz-Ran spaces are functorial both in the nice couple and in the PMQ-group pair. For a locally finite PMQ Q\mathcal{Q} we prove a homeomorphism between Hur((0,1)2;Q+)\mathrm{Hur}((0,1)^2;\mathcal{Q}_+) and the simplicial Hurwitz space HurΔ(Q)\mathrm{Hur}^{\Delta}(\mathcal{Q}), introduced in previous work of the author: this provides in particular Hur((0,1)2;Q+)\mathrm{Hur}((0,1)^2;\mathcal{Q}_+) with a cell stratification in the spirit of Fox-Neuwirth and Fuchs.

Keywords

Cite

@article{arxiv.2107.01167,
  title  = {Hurwitz-Ran spaces},
  author = {Andrea Bianchi},
  journal= {arXiv preprint arXiv:2107.01167},
  year   = {2023}
}

Comments

52 pages, 9 figures, the title has been changed according to the suggestion of the referee. To appear in Geometriae Dedicata

R2 v1 2026-06-24T03:51:01.872Z