Thin monodromy in O(5)

Abstract

This article studies the orthogonal hypergeometric groups of degree five. We establish the thinness of 12 out of the 19 hypergeometric groups of type O(3,2) from [4, Table 6]. Some of these examples are associated with Calabi-Yau 4-folds. We also establish the thinness of 9 out of the 17 hypergeometric groups of type O(4,1) from [12], where the thinness of 7 other cases was already proven. The O(4,1) type groups were predicted to be all thin and our result leaves just one case open.