2008/02/20 by Alex James Bene, Bene, Alex James · 1 citation
Mathematics · #05C25 #14H10 #20F34 #20F38 (Primary) #20F99 (Secondary) #32G15 #57M99 #Algebraic Geometry and Number Theory #FOS: Mathematics #Geometric Topology (math.GT) #Geometric and Algebraic Topology #Homotopy and Cohomology in Algebraic Topology #math.GT #msc:05C25 #msc:14H10 #msc:20F34 #msc:20F38 #msc:20F99 #msc:32G15 #msc:57M99
paper · pdf · doi:10.48550/arxiv.0802.2747
27 pages, 11 figures, 1 equation
arxiv created 2008/02/20 · openalex publication_date 2008/02/20 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The Ptolemy groupoid is a combinatorial groupoid generated by elementary moves on marked trivalent fatgraphs with three types of relations. Through the fatgraph decomposition of Teichmüller space, the Ptolemy groupoid is a mapping class group equivariant subgroupoid of the fundamental path groupoid of Teichmüller space with a discrete set objects. In particular, it leads to an infinite, but combinatorially simple, presentation of the mapping class group of an orientable surface. In this note, we give a presentation of a full mapping class group equivariant subgroupoid of the Ptolemy groupoid of an orientable surface with one boundary component in terms of marked linear chord diagrams, with chord slides as generators and five types of relations. We also introduce a dual version of this presentation which has advantages for certain applications, one of which is given.