TY - JOUR

T1 - A new intrinsically knotted graph with 22 edges

AU - Kim, Hyoungjun

AU - Lee, Hwa Jeong

AU - Lee, Minjung

AU - Mattman, Thomas

AU - Oh, Seungsang

N1 - Funding Information:
The fifth author was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. NRF-2014R1A2A1A11050999).
Publisher Copyright:
© 2017 Elsevier B.V.

PY - 2017/9/1

Y1 - 2017/9/1

N2 - A graph is called intrinsically knotted if every embedding of the graph contains a knotted cycle. Johnson, Kidwell, and Michael showed that intrinsically knotted graphs have at least 21 edges. Recently Lee, Kim, Lee and Oh (and, independently, Barsotti and Mattman) proved there are exactly 14 intrinsically knotted graphs with 21 edges by showing that H12 and C14 are the only triangle-free intrinsically knotted graphs of size 21. Our current goal is to find the complete set of intrinsically knotted graphs with 22 edges. To this end, using the main argument in [9], we seek triangle-free intrinsically knotted graphs. In this paper we present a new intrinsically knotted graph with 22 edges, called M11. We also show that there are exactly three triangle-free intrinsically knotted graphs of size 22 among graphs having at least two vertices with degree 5: cousins 94 and 110 of the E9+e family, and M11. Furthermore, there is no triangle-free intrinsically knotted graph with 22 edges that has a vertex with degree larger than 5.

AB - A graph is called intrinsically knotted if every embedding of the graph contains a knotted cycle. Johnson, Kidwell, and Michael showed that intrinsically knotted graphs have at least 21 edges. Recently Lee, Kim, Lee and Oh (and, independently, Barsotti and Mattman) proved there are exactly 14 intrinsically knotted graphs with 21 edges by showing that H12 and C14 are the only triangle-free intrinsically knotted graphs of size 21. Our current goal is to find the complete set of intrinsically knotted graphs with 22 edges. To this end, using the main argument in [9], we seek triangle-free intrinsically knotted graphs. In this paper we present a new intrinsically knotted graph with 22 edges, called M11. We also show that there are exactly three triangle-free intrinsically knotted graphs of size 22 among graphs having at least two vertices with degree 5: cousins 94 and 110 of the E9+e family, and M11. Furthermore, there is no triangle-free intrinsically knotted graph with 22 edges that has a vertex with degree larger than 5.

KW - Intrinsically knotted

KW - Spatial graph

UR - http://www.scopus.com/inward/record.url?scp=85021108205&partnerID=8YFLogxK

U2 - 10.1016/j.topol.2017.06.013

DO - 10.1016/j.topol.2017.06.013

M3 - Article

AN - SCOPUS:85021108205

SN - 0166-8641

VL - 228

SP - 303

EP - 317

JO - Topology and its Applications

JF - Topology and its Applications

ER -