The Elementary Divisors of the Incidence Matrices of Skew Lines in PG(3,p)

The elementary divisors of the incidence matrices of lines in $PG(3,p)$ are computed, where two lines are incident if and only if they are skew.Comment: 9 page

Some simple modules for classical groups and pp-ranks of orthogonal and Hermitian geometries

We determine the characters of the simple composition factors and the submodule lattices of certain Weyl modules for classical groups. The results have several applications. The simple modules arise in the study of incidence systems in finite geometries and knowledge of their dimensions yields the $p$-ranks of these incidence systems.Comment: 33 pages, corrected parity of u in statement of Theorem 1.6(b