doi:10.1016/j.disc.2003.04.001
Copyright © 2003 Elsevier B.V. All rights reserved.
Transitivity of local complementation and switching on graphs
a Department of Computer Science, University of Colorado at Boulder, Boulder, CO 80309-0347, USA
b Department of Mathematics, University of Turku, FIN-20014, Turku, Finland
c Leiden Institute of Advanced Computer Science, Leiden University, P.O. Box 9512, 2300 RA, Leiden, Netherlands
Received 30 January 2002;
Revised 28 April 2003;
accepted 26 May 2003.
Available online 1 March 2004.
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Abstract
The operations complementation C, local complementation λx, and switching σx for the vertices x of a finite undirected graph are considered. The operation λx complements the subgraph induced by the neighbourhood of x in the given graph, and the switching σx changes the neighbourhood of x to its complement vertex set. It is proved that the compositions δx=λxC (for vertices x
D) generate a transitive group on the graphs with vertex set D, that is, for any two graphs g and h on D, there exists a composition α of operations δx such that h=α(g). It is also shown that the compositions τx=λxσx (for x
D) generate a transitive group on the graphs.
Author Keywords: Author Keywords: Finite graph; Local complementation; Switching; Transitive group; Composition of operations
Fig. 1. Switchings of the graph g.
Fig. 2. Local complementations of the graph g.
Fig. 3. Derivation of CλxC(g).
Fig. 4. Derivation of σxλxσx(g).
Fig. 5. Derivation of Cηx(g)=Cλxσxλx(g).
Fig. 6. Derivation of ηxC(g)=λxσxλxC(g).
Fig. 7. Case |D|=4 for
C,Λ
D.
Fig. 8. The diagrams for g, δx(g) and δ−1x(g)=Cλx(g).
Fig. 9. The diagrams for g, λyλx(g), σyσxλyλx(g) and α(g).
Fig. 10. The diagrams for σyα(g), λxσyα(g), λyλxσy(g) and β(g).
Fig. 11. The diagrams for σxβ(g), λyσxβ(g), and C(g)=λxλyσyβ(g).
Fig. 12. g
A=σA(x)λxσA(x)(g), where A=X2
Y1 and A(x)=X1
X2.
Fig. 13. The diagrams for τx(g)=λxσx(g) and τ−1x(g)=σxλx(g).
Fig. 14. The graphs in the proof of Theorem 21.
Fig. 15. The derivation of α(g) for α=ηxσAC.