Multi-Way Expanders and Imprimitive Group Actions on Graphs

作者:Mimura Masato*
来源:International Mathematics Research Notices, 2016, 2016(8): 2522-2543.
DOI:10.1093/imrn/rnv220

摘要

For n >= 2, the concept of n-way expanders was defined by many researchers. Bigger n gives a weaker notion in general, and 2-way expanders coincide with expanders in usual sense. Koji Fujiwara asked whether these concepts are equivalent to that of ordinary expanders for all n for a sequence of Cayley graphs. In this paper, we answer his question in the affirmative. Furthermore, we obtain universal inequalities on multi-way isoperimetric constants on any finite connected vertex-transitive graph, and show that gaps between these constants imply the imprimitivity of the group action on the graph.

  • 出版日期2016