English

Origami edge-paths in the curve graph

Geometric Topology 2021-05-11 v2

Abstract

An "origami" (or flat structure) on a closed oriented surface, SgS_g, of genus g2g \geq 2 is obtained from a finite collection of unit Euclidean squares by gluing each right edge to a left one and each top edge to a bottom one. The main objects of study in this note are "origami pairs of curves" -- filling pairs of simple closed curves, (α,β) (\alpha,\beta), in SgS_g such that their minimal intersection is equal to their algebraic intersection -- they are "coherent". An origami pair of curves is naturally associated with an origami on SgS_g. Our main result establishes that for any origami pair of curves there exists an "origami edge-path", a sequence of curves, α=α0,α1,α2,,αn=β\alpha =\alpha_0, \alpha_1, \alpha_2, \cdots, \alpha_n = \beta , such that: αi\alpha_i intersects αi+1\alpha_{i+1} at exactly once; any pair (αi,αj)(\alpha_i, \alpha_j) is coherent; and thus, any filling pair, (αi,αj)(\alpha_i, \alpha_j), is also an origami. With their existence established, we offer shortest origami edge-paths as an area of investigation.

Keywords

Cite

@article{arxiv.2008.09179,
  title  = {Origami edge-paths in the curve graph},
  author = {Hong Chang and Xifeng Jin and William W. Menasco},
  journal= {arXiv preprint arXiv:2008.09179},
  year   = {2021}
}

Comments

14 pages, 9 figures. To appear in Topology & Its Applications. This final version before publication includes numerous minor edits to the text and figures that were suggested by referee

R2 v1 2026-06-23T18:00:05.251Z