Projective Geometric Codes

In this article, we determine the words of minimum weight in the code of the incidence system of s- versus t-flats in a finite projective space. Our proof depends on a few combinatorial results on the geometry of flats which may be of independent interest. We also give bounds for the minimum weight of the dual of this code and show that they are attained in many cases. The lower bound is a consequence of a general result on the dual code of an incidence system.