On some Siegel threefold related to the tangent cone of the Fermat quartic surface

Takeo Okazaki, Takuya Yamauchi

Let $Z$ be the quotient of the Siegel modular threefold ${\mathcal{A}}^{\mathrm{sa}}(2,4,8)$ which has been studied by van Geemen and Nygaard. They gave an implication that some 6-tuple $…