I need to prove the existence of the $(1944, 144, 0.5)$ spectral expander. I tried to construct it using tensor product of the following graphs: $$ (1944, 144, 0.5) = (9^2, 9, 1/3) \otimes (24, 16, 0.5) $$ I already know that expander with parameters $(9^2, 9, 1/3)$ exists and corresponds to the affine expander, but I am not sure about $(24, 16, 0.5)$ one.
1 Answer
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There are also expanders with the following parameters: $(3, 2, 1/2)$ — complete graph on 3 vertices and $(8,8, 0)$ — complete graph on 8 vertices with the loop in each vertex. So we have the following tensor product: $$ (1944, 144, 0.5) = (9^2, 9, 1/3) \otimes (3, 2, 1/2) \otimes (8,8, 0) $$