In this short note the neighbourhood graph of a Cayley graph is considered. It has, as nodes, a symmetric generating set of a finitely-generated group . Two nodes are connected by an edge if one is obtained from the other by multiplication on the right by one of the generators. Two necessary conditi
Expansion Properties of Cayley Graphs of the Alternating Groups
β Scribed by Yuval Roichman
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 360 KB
- Volume
- 79
- Category
- Article
- ISSN
- 0097-3165
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β¦ Synopsis
Let C be a conjugacy class in the alternating group A n , and let supp(C) be the number of nonfixed digits under the action of a permutation in C. For every 1>$>0 and n 5 there exists a constant c=c($)>0 such that if supp(C) $n then the undirected Cayley graph X(A n , C) is a c expander. A family of such Cayley graphs with supp(C)=o(-n) is not a family of c-expanders. For every $>0, if supp(C) -3n then sets of vertices of order at most ( 12 &$)(n&(nΓsupp(C)))! in X(A n , C) expand. The proof of the last result combines spectral and representation theory techniques with direct combinatorial arguments. 1997 Academic Press the following problem [Lu1, 10.3.4 10.3.5]: Can the symmetric groups (or families of groups of Lie type over a fixed finite field) be made a family of Cayley graphs which are c-expanders? See also [BHKLS]. The case of article no. TA972786 281 0097-3165Γ97 25.00
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