Association Schemes with Multiple Q-polynomial Structures |
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| Authors: | Hiroshi Suzuki |
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| Affiliation: | (1) Department of Mathematics, International Christian University, 10-2, Osawa 3-chome, Mitaka-shi Tokyo, 181, Japan |
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| Abstract: | It is well known that an association scheme  with  has at most two P-polynomial structures. The parametrical condition for an association scheme to have two P-polynomial structures is also known. In this paper, we give a similar result for Q-polynomial association schemes. In fact, if  , then we obtain exactly the same parametrical conditions for the dual intersection numbers or Krein parameters. |
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| Keywords: | Q-polynomial association scheme multiple Q-polynomial structure Krein parameter distance-regular graph integrality of eigenvalue |
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