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Shadows of $2$–knots and complexity

Hironobu Naoe

Algebraic & Geometric Topology 24 (2024) 4651–4695
Abstract

We introduce a new invariant for a 2–knot in S4, called the shadow-complexity, based on the theory of Turaev shadows, and we give a characterization of 2–knots with shadow-complexity at most 1. Specifically, we show that the unknot is the only 2–knot with shadow-complexity 0 and that there exist infinitely many 2–knots with shadow-complexity 1.

Keywords
2–knot, Turaev shadow, 4–manifold, complexity, banded unlink diagram
Mathematical Subject Classification
Primary: 57K40, 57K45
Secondary: 57R65
References
Publication
Received: 9 November 2022
Revised: 9 May 2023
Accepted: 2 August 2023
Published: 17 December 2024
Authors
Hironobu Naoe
Department of Mathematics
Tokyo Institute of Technology
Tokyo
Japan

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