Wolfgang Bertram
(2003)
We characterize an important class of generalized projective geometries by the
following essentially equivalent properties: (1) admits a central null-system;
(2) admits inner polarities: (3) is associated to a unital Jordan
algebra. These geometries, called of the first kind, play in the category of generalized
projective geometries a rôle comparable to the one of the projective line in the category
of ordinary projective geometries. In this general set-up, we prove an analogue...