Segment number of knots

In this paper, we introduce a new numerical knot invariant, termed the segment number, which is derived from partitioned knot diagrams subject to specific over/under-crossing constraints. We prove that a knot is non-trivial if and only if its segment number is at least 3. Furthermore, we investigate the structural properties of the directed graph associated with a minimal segment number presentation. Specifically, we show that for any minimal presentation, the underlying graph is connected and cannot be a path. Finally, we discuss the relationship between the segment number and the bridge number, providing bounds and conjectures for future study. We also conjecture that the bridge number [Formula: see text] provides a lower bound for the segment number.

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Publication Details

Journal
Journal of Knot Theory and Its Ramifications
Published
2026-02-27
DOI
https://doi.org/10.1142/s0218216526500215
Primary Topic
Geometric and Algebraic Topology
Type
article
Field-Weighted Citation Impact
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article

Segment number of knots

Makoto Ozawa
Journal of Knot Theory and Its Ramifications
Geometric and Algebraic Topology
article

Segment number of knots

Makoto Ozawa
article en

Abstract

In this paper, we introduce a new numerical knot invariant, termed the segment number, which is derived from partitioned knot diagrams subject to specific over/under-crossing constraints. We prove that a knot is non-trivial if and only if its segment number is at least 3. Furthermore, we investigate the structural properties of the directed graph associated with a minimal segment number presentation. Specifically, we show that for any minimal presentation, the underlying graph is connected and cannot be a path. Finally, we discuss the relationship between the segment number and the bridge number, providing bounds and conjectures for future study. We also conjecture that the bridge number [Formula: see text] provides a lower bound for the segment number.

Journal of Knot Theory and Its Ramifications
Komazawa University (JP)
Openalex Percentile: Top 37%
Geometric and Algebraic Topology
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