,
Clément Maria
Creative Commons Attribution 4.0 International license
3-manifolds are commonly represented as triangulations, consisting of abstract tetrahedra whose triangular faces are identified in pairs. The combinatorial sparsity of a triangulation, as measured by the treewidth of its dual graph, plays a fundamental role in the design of parameterized algorithms. In this work, we investigate algorithmic procedures that transform or modify a given triangulation while controlling specific sparsity parameters. First, we revisit a standard, linear-time algorithm that converts a given triangulation into a Heegaard diagram of the underlying 3-manifold, showing that the construction preserves treewidth. We apply this construction to exhibit a fixed-parameter tractable framework for computing Kuperberg’s quantum invariants of 3-manifolds. Second, we present a quasi-linear-time algorithm that retriangulates a given triangulation into one with maximum edge valence of at most nine, while only moderately increasing the treewidth of the dual graph. Combining these two algorithms yields a quasi-linear-time algorithm that produces, from a given triangulation, a Heegaard diagram in which every attaching curve intersects at most nine others.
@InProceedings{huszar_et_al:LIPIcs.SoCG.2026.58,
author = {Husz\'{a}r, Krist\'{o}f and Maria, Cl\'{e}ment},
title = {{On Sparse Representations of 3‑Manifolds}},
booktitle = {42nd International Symposium on Computational Geometry (SoCG 2026)},
pages = {58:1--58:18},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-418-5},
ISSN = {1868-8969},
year = {2026},
volume = {367},
editor = {Ahn, Hee-Kap and Hoffmann, Michael and Nayyeri, Amir},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2026.58},
URN = {urn:nbn:de:0030-drops-258659},
doi = {10.4230/LIPIcs.SoCG.2026.58},
annote = {Keywords: computational 3-manifold topology, fixed-parameter tractability, Heegaard splittings and diagrams, triangulations, edge valence, treewidth, quantum invariants, tensor networks}
}