A generalization of Filliman duality

Greg Kuperberg

Published 2001-12-07, updated 2002-07-10Version 3

Filliman duality expresses (the characteristic measure of) a convex polytope P containing the origin as an alternating sum of simplices that share supporting hyperplanes with P. The terms in the alternating sum are given by a triangulation of the polar body P^o. The duality can lead to useful formulas for the volume of P. A limiting case called Lawrence's algorithm can be used to compute the Fourier transform of P. In this note we extend Filliman duality to an involution on the space of polytopal measures on a finite-dimensional vector space, excluding polytopes that have a supporting hyperplane coplanar with the origin. As a special case, if P is a convex polytope containing the origin, any realization of P^o as a linear combination of simplices leads to a dual realization of P.