English

Nonexistence of Exceptional 5-class Association Schemes with Two $Q$-polynomial Structures

Combinatorics 2013-11-26 v1

Abstract

In [H. Suzuki, Association schemes with multiple QQ-polynomial structures, J. Algebraic Combin. 7 (1998) 181-196], Suzuki gave a classification of association schemes with multiple QQ-polynomial structures, allowing for one exceptional case which has five classes. In this paper, we rule out the existence of this case. Hence Suzuki's theorem mirrors exactly the well-known counterpart for association schemes with multiple PP-polynomial structures, a result due to Eiichi Bannai and Etsuko Bannai in 1980.

Keywords

Cite

@article{arxiv.1311.5942,
  title  = {Nonexistence of Exceptional 5-class Association Schemes with Two $Q$-polynomial Structures},
  author = {Jianmin Ma and Kaishun Wang},
  journal= {arXiv preprint arXiv:1311.5942},
  year   = {2013}
}

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8 pages