English

Efficient triangulations and boundary slopes

Geometric Topology 2020-06-29 v1

Abstract

For a compact, irreducible, \partial-irreducible, an-annular bounded 3-manifold MB3M\ne\mathbb{B}^3, then any triangulation T\mathcal{T} of MM can be modified to an ideal triangulation T\mathcal{T}^* of M\stackrel{\circ}{M}. We use the inverse relationship of crushing a triangulation along a normal surface and that of inflating an ideal triangulation to introduce and study boundary-efficient triangulations and end-efficient ideal triangulations. We prove that the topological conditions necessary for a compact 3-manifold MM admitting an annular-efficient triangulation are sufficient to modify any triangulation of MM to a boundary-efficient triangulation which is also annular-efficient. From the proof we have for any ideal triangulation TT^* and any inflation TΛ\mathcal{T}_{\Lambda}, there is a bijective correspondence between the closed normal surfaces in T\mathcal{T}^* and the closed normal surfaces in TΛ\mathcal{T}_{\Lambda} with corresponding normal surfaces being homeomorphic. It follows that for an ideal triangulation T\mathcal{T}^* that is 00-efficient, 11-efficient, or end-efficient, then any inflation TΛ\mathcal{T}_{\Lambda} of T\mathcal{T}^* is 00-efficient, 11-efficient, or \partial-efficient, respectively. There are algorithms to decide if a given triangulation or ideal triangulation of a 33-manifold is one of these efficient triangulations. Finally, it is shown that for an annular-efficient triangulation, there are only a finite number of boundary slopes for normal surfaces of a bounded Euler characteristic; hence, in a compact, orientable, irreducible, \partial-irreducible, and an-annular 33-manifold, there are only finitely many boundary slopes for incompressible and \partial-incompressible surfaces of a bounded Euler characteristic.

Keywords

Cite

@article{arxiv.2006.14701,
  title  = {Efficient triangulations and boundary slopes},
  author = {Birch Bryant and William Jaco and J. Hyam Rubinstein},
  journal= {arXiv preprint arXiv:2006.14701},
  year   = {2020}
}

Comments

21 pages, 6 figures; revised and improved version of an earlier paper arXiv:1108.2936, Annular efficient triangulations of 3-manifolds

R2 v1 2026-06-23T16:38:16.202Z