Polynomial-Time Algorithms for Links
Abstract
Every link in the 3-sphere admits a generalised T-link presentation. In this paper, we give an explicit polynomial-time algorithm which, given a signed Artin braid word and the number of strands, computes such a presentation. Combining this construction with Yamada--Vogel braiding gives a polynomial-time conversion from arbitrary oriented combinatorial link diagrams to generalised T-link parameters. We prove polynomial bounds on the number of strands and crossings in the resulting braid. As an application, we prove that a link property or a link invariant is computable in polynomial time from diagrams if and only if the corresponding problem is solvable in polynomial time from generalised T-link parameters, with parameter input measured by the total number of strands and crossings in the corresponding braid diagram. Whenever a classification criterion or an explicit invariant formula is available in these parameters, it can be applied to the original link by substituting the parameters obtained from the diagram. A polynomial-time test or evaluation then gives a polynomial-time procedure on diagrams. We also establish the corresponding transfer for approximating real-valued invariants to prescribed accuracy.
Related
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BibTeX
@misc{paiva2026polynomialtime,
title = {{Polynomial-Time Algorithms for Links}},
author = {Thiago de Paiva and Yi Liu},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.42077},
eprint = {2610.42077},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.42077},
}
RIS
TY - UNPB
TI - Polynomial-Time Algorithms for Links
AU - Thiago de Paiva
AU - Yi Liu
PY - 2026
DA - 2026/10/30
PB - arXiv
DO - 10.48550/arxiv.2610.42077
UR - https://arxiv.org/abs/2610.42077
AB - Every link in the 3-sphere admits a generalised T-link presentation. In this paper, we give an explicit polynomial-time algorithm which, given a signed Artin braid word and the number of strands, computes such a presentation. Combining this construction with Yamada--Vogel braiding gives a polynomial-time conversion from arbitrary oriented combinatorial link diagrams to generalised T-link parameters. We prove polynomial bounds on the number of strands and crossings in the resulting braid. As an application, we prove that a link property or a link invariant is computable in polynomial time from diagrams if and only if the corresponding problem is solvable in polynomial time from generalised T-link parameters, with parameter input measured by the total number of strands and crossings in the corresponding braid diagram. Whenever a classification criterion or an explicit invariant formula is available in these parameters, it can be applied to the original link by substituting the parameters obtained from the diagram. A polynomial-time test or evaluation then gives a polynomial-time procedure on diagrams. We also establish the corresponding transfer for approximating real-valued invariants to prescribed accuracy.
ER -