English

The Thurston norm via spun-normal immersions

Geometric Topology 2021-09-13 v1

Abstract

A theory of transversely oriented spun-normal immersed surfaces in ideally triangulated 3--manifolds is developed in this paper, including linear functionals determining the boundary curves, Euler characteristic and homology class of these immersions. This is used to develop and implement an algorithm to compute the unit ball of the Thurston norm for cusped hyperbolic 3--manifolds of finite volume. As an application of independent interest, we give an upper bound on the minimal entropy of pseudo-Anosov maps of surfaces with number of cusps bounded linearly in genus.

Keywords

Cite

@article{arxiv.2109.04498,
  title  = {The Thurston norm via spun-normal immersions},
  author = {Daryl Cooper and Stephan Tillmann and William Worden},
  journal= {arXiv preprint arXiv:2109.04498},
  year   = {2021}
}

Comments

37 pages, 13 figures

R2 v1 2026-06-24T05:50:22.606Z