Let V be a 3-dimensional vector space over a finite field. We show that any irreducible subgroup of GL(V ) that arises as the automorphism group of an regular polytope preserves a nondegenerate symmetric bilinear form on V . In particular, the only classical groups on V that arise as automorphisms of such polytopes are the orthogonal groups.
Peter A. Brooksbank, Deborah A. Vicinsky