Nonexistence of exceptional imprimitive Q-polynomial association schemes with six classes

Hajime Tanaka, Rie Tanaka

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

Suzuki (1998) [9] showed that an imprimitive Q-polynomial association scheme with first multiplicity at least 3 is Q-bipartite, or is Q-antipodal, or has four or six classes. The exceptional case with four classes has recently been ruled out by Cerzo and Suzuki (2009) [5]. In this paper, we show the nonexistence of the last case with six classes. Hence Suzuki's theorem now exactly mirrors its well-known counterpart for imprimitive distance-regular graphs.

Original languageEnglish
Pages (from-to)155-161
Number of pages7
JournalEuropean Journal of Combinatorics
Volume32
Issue number2
DOIs
Publication statusPublished - 2011 Feb

ASJC Scopus subject areas

  • Discrete Mathematics and Combinatorics

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