Fusions of the generalized Hamming scheme on a strongly-regular graph

Abstract

In this paper we show that for any fusion $\mathcal{B}$ of an association scheme $\mathcal{A}$, the generalized Hamming scheme $H(n,\mathcal{B})$ is a nontrivial fusion of $H(n,\mathcal{A})$. We analyze the case where $\mathcal{A}$ is the association scheme on a strongly-regular graph, and determine the parameters of all strongly-regular graphs for which the generalized Hamming scheme, $H(2,\mathcal{A})$, has extra fusions, in addition to the one arising from the trivial fusion of $\mathcal{A}$.