Published online by Cambridge University Press: 07 September 2023
Edge-to-edge tilings of the sphere by congruent quadrilaterals are completely classified in a series of three papers. This second one applies the powerful tool of trigonometric Diophantine equations to classify the case of $a^3b$-quadrilaterals with all angles being rational degrees. There are
$12$ sporadic and
$3$ infinite sequences of quadrilaterals admitting the two-layer earth map tilings together with their modifications, and
$3$ sporadic quadrilaterals admitting
$4$ exceptional tilings. Among them only three quadrilaterals are convex. New interesting non-edge-to-edge triangular tilings are obtained as a byproduct.
This research was supported by key projects of Zhejiang Natural Science Foundation No. LZ22A010003 and ZJNU Shuang-Long Distinguished Professorship Fund No. YS304319159.