12-DIMENSIONAL ASPECTS OF 4-DIMENSIONAL N=1 TYPE-I VACUA

Four-dimensional supergravity theories are reinterpreted in a 12-dimen sional F-theory framework, The O(8) symmetry of N = 8 supergravity is related to a reduction of F-theory on T-8, with the seventy scalars fo rmally associated, by O(8) triality, to a fully compactified four-form A(4). For the N = 1 type I model recently obtained from the type IIB string on the Z orbifold, we identify the Kahler manifold of the untwi sted scalars in the unoriented closed sector with the generalized Sieg el upper-half plane Sp(8,R)/(SU(4) x U(1)). The SU(4) factor reflects the holonomy group of Calabi-Yau four-folds.