Lorentzian Lattices and E-Polytopes

Abstract

We consider certain En-type root lattices embedded within the standard Lorentzian lattice Z(n+1) (3 <= n <= 8) and study their discrete geometry from the point of view of del Pezzo surface geometry. The lattice Z(n+1) decomposes as a disjoint union of affine hyperplanes which satisfy a certain periodicity. We introduce the notions of line vectors, rational conic vectors, and rational cubics vectors and their relations to E-polytopes. We also discuss the relation between these special vectors and the combinatorics of the Gosset polytopes of type (n-4)(21).