An excess theorem for spherical 2-designs
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- Kurihara, H. Des. Codes Cryptogr. (2012) 65: 89. doi:10.1007/s10623-012-9677-3
We give an excess theorem for spherical 2-designs. This theorem is a dual version of the spectral excess theorem for graphs, which gives a characterization of distance-regular graphs, among regular graphs in terms of the eigenvalues and the excess. Here we give a characterization of Q-polynomial association schemes among spherical 2-designs.