Some large trivalent graphs having small diameters
Discrete Applied Mathematics - Special double volume: interconnection networks
Concrete Math
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We show that for integers k=2 and n=3, the diameter of the Cayley graph of SL"n(Z/kZ) associated with a standard two-element generating set is at most a constant times n^2lnk. This answers a question of A. Lubotzky concerning SL"n(F"p) and is unexpected because these Cayley graphs do not form an expander family. Our proof amounts to a quick algorithm for finding short words representing elements of SL"n(Z/kZ). We generalize our results to other Chevalley groups over Z/kZ.