An identity theorem for the Fourier transform of polytopes on rationally parameterisable hypersurfaces

TL;DR

This paper establishes an identity theorem for the Fourier transform of generalized polytopes on rationally parameterisable hypersurfaces, with applications to quadrics like spheres, ensuring uniqueness of the polytope from its transform.

Contribution

It proves a new identity theorem linking Fourier transforms of polytopes on rational hypersurfaces, extending uniqueness results to a broader class including spheres.

Findings

Fourier transform equality implies polytope equality on certain hypersurfaces

The theorem applies to quadrics without lines, such as spheres

Provides conditions under which the transform uniquely determines the polytope

Abstract

A set $\mathcal{S}$ of points in $\mathbb{R}^n$ is called a rationally parameterisable hypersurface if $\mathcal{S}=\{\boldsymbol{\sigma}(\mathbf{t}): \mathbf{t} \in D\}$, where $\boldsymbol{\sigma}: \mathbb{R}^{n-1} \rightarrow \mathbb{R}^n$ is a vector function with domain $D$ and rational functions as components. A generalized $n$-dimensional polytope in $\mathbb{R}^n$ is a union of a finite number of convex $n$-dimensional polytopes in $\mathbb{R}^n$. The Fourier transform of such a generalized polytope $\mathcal{P}$ in $\mathbb{R}^n$ is defined by $F_{\mathcal{P}}(\mathbf{s})=\int_{\mathcal{P}} e^{-i\mathbf{s}\cdot\mathbf{x}} \,\mathbf{dx}$. We prove that $F_{\mathcal{P}_1}(\boldsymbol{\sigma}(\mathbf{t})) = F_{\mathcal{P}_2}(\boldsymbol{\sigma}(\mathbf{t}))\ \forall \mathbf{t} \in O$ implies $\mathcal{P}_1=\mathcal{P}_2$ if $O$ is an open subset of $D$ satisfying some well-defined conditions. Moreover we show that this theorem can be applied to quadric hypersurfaces that do not contain a line, but at least two points, i.e., in particular to spheres.