The integer point transform as a complete invariant

Abstract

The integer point transform $\sigma_\PP$ is an important invariant of a rational polytope $\PP$, and here we show that it is a complete invariant. We prove that it is only necessary to evaluate $\sigma_\PP$ at one algebraic point in order to uniquely determine $\PP$, by employing the Lindemann-Weierstrass theorem. Similarly, we prove that it is only necessary to evaluate the Fourier transform of a rational polytope $\PP$ at a single algebraic point, in order to uniquely determine $\PP$. We prove that identical uniqueness results also hold for integer cones. In addition, by relating the integer point transform to finite Fourier transforms, we show that a finite number of \emph{integer point evaluations} of $\sigma_\PP$ suffice in order to uniquely determine $\PP$. We also give an equivalent condition for central symmetry of a finite point set, in terms of the integer point transform, and prove some facts about its local maxima. Most of the results are proven for arbitrary finite sets of integer points in $\R^d$.