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Knödel Graph


The Knödel graph W_(Delta,n) is a regular bipartite graph of vertex degree Delta on n nodes for even n>=2 and 1<=Delta<=|_log_2n_| with edges defined as follows. Label the vertices (i,j) with i=1,2 and 0<=j<=n/2-1. Then there is an edge between (1,j) and (2,k) for every k=j+2^p-1 (mod n/2) where p=0, ..., Delta-1 (Fertin and Raspaud 2004, Clancy et al. 2019).

This class of graphs was introduced by Knödel (1975) in constructing a time-optimal algorithm for gossiping among n vertices with even n, but were only formally defined by Fraigniaud and Peters (2001) (Fertin and Raspaud 2004).

Knödel graphs are Cayley and vertex-transitive graphs (Fertin and Raspaud 2004). They are also Haar graphs.

Special cases are summarized in the following table.

The edge connectivity of W_(Delta,n) is given by

 lambda(W_(Delta,n))=Delta
(1)

and the vertex connectivity satisfies

 2/3Delta<kappa(W_(Delta,n))<=Delta
(2)

(Fertin and Raspaud 2004).

Zheng et al. (2008) showed that the graph crossing numbers of the cubic Knödel graph W_(3,n) is given by

cr(W_(3,8))=0
(3)
cr(W_(3,10))=1
(4)
cr(W_(3,n))=|_n/6_|+(n (mod 6))/2
(5)

for even n>=12 (Clancy et al. 2019).


See also

Cycle Graph, Haar Graph, Honeycomb Toroidal Graph, I Graph, Ladder Rung Graph

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References

Clancy, K.; Haythorpe, M.; and Newcombe, A. "Knödel Graph." §2.6 in "A Survey of Graphs with Known or Bounded Crossing Numbers." 15 Feb 2019. https://arxiv.org/pdf/1901.05155.pdf.Fertin, G. and Raspaud, A. "A Survey on Knödel Graphs." Disc. Appl. Math. 137, 173-195, 2004.Fraigniaud, P. and Peters, J. G. "Minimum Linear Gossip Graphs and Maximal Linear (Delta;k)-Gossip Graphs." Networks 38, 150-162, 2001.Knödel, W. "New Gossips and Telephones." Disc. Math. 13, 95, 1975.Zheng, W.; Lin, X.; Yang, Y.; and Deng, C. "The Crossing Number of Knödel Graph W_(3,n)." Util. Math. 75, 211-224, 2008.

Cite this as:

Weisstein, Eric W. "Knödel Graph." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/KnoedelGraph.html

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