Yanzhen Xiong

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math.CO2026

Characterizations of amorphic association schemes in terms of fusing triples

Yanzhen Xiong

Let $R$ be an association scheme with nontrivial relations $A_{1}, \dots, A_{d}$ . We call $R$ amorphic if every possible fusion of its nontrivial relations gives ris…

math.CO2026

Almost amorphic association schemes

Edwin van Dam, Jack H. Koolen, Yanzhen Xiong

An association scheme is called amorphic if every possible fusion of relations gives rise to another association scheme. In earlier work, we showed that if an association scheme ha…

math.CO2024

Characterizations of amorphic schemes and fusions of pairs

Edwin R. van Dam, Jack H. Koolen, Yanzhen Xiong

An association scheme is called amorphic if every possible fusion of relations gives rise to a fusion scheme. We call a pair of relations fusing if fusing that pair gives rise to a…