This paper completes the classification of antipodal distance-transitive covers of the complete bipartite graphs K k , k , where k Ρ 3 . For such a cover the antipodal blocks must have size r Ρ k . Although the case r Ο k has already been considered , we give a unified treatment of r Ρ k . We use d
Antipodal Distance Transitive Covers of Complete Graphs
β Scribed by C.D. Godsil; R.A. Liebler; C.E. Praeger
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 352 KB
- Volume
- 19
- Category
- Article
- ISSN
- 0195-6698
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β¦ Synopsis
A distance-transitive antipodal cover of a complete graph K n possesses an automorphism group that acts 2-transitively on the fibres. The classification of finite simple groups implies a classification of finite 2-transitive permutation groups, and this allows us to determine all possibilities for such a graph. Several new infinite families of distance-transitive graphs are constructed.
π SIMILAR VOLUMES
Let 1 be a distance-regular graph of diameter d and valency k>2. If b t =1 and 2t d, then 1 is an antipodal double-cover. Consequently, if f >2 is the multiplicity of an eigenvalue of the adjacency matrix of 1 and if 1 is not an antipodal doublecover then d 2f&3. This result is an improvement of God
Regular covers of complete graphs which are 2-arc-transitive are investigated. A classification is given of all such graphs whose group of covering transformations is either cyclic or isomorphic to Z p \_Z p , where p is a prime and whose fibrepreserving subgroup of automorphisms acts 2-arc-transiti
We show that a distance-regular graph of valency k ΟΎ 2 is antipodal , if b 2 Ο 1 . This answers Problem (i) on p . 182 of Brouwer , Cohen and Neumaier [4] .
An antipodal distance-regular graph of diameter four or five is a covering graph of a connected strongly regular graph. We give existence conditions for these graphs and show for some types of strongly regular graphs that no nontrivial covers exist.
Let 1 denote a bipartite Q-polynomial distance-regular graph with diameter D 4. We show that 1 is the quotient of an antipodal distance-regular graph if and only if one of the following holds. (i) 1 is a cycle of even length. (ii) 1 is the quotient of the 2D-cube. 1999 Academic Press \* , ..., %\