# Welcome to structure-factor’s documentation:

This is the documentation of the `structure-factor`

open-source Python project which currently collects

various estimators of the structure factor,

several diagnostics of hyperuniformity,

for stationary and isotropic point processes.

source code GitHub

tutorial Jupyter notebook

## Introduction

Hyperuniformity is the study of stationary point processes with a sub-Poisson variance of the number of points in a large window. For the homogeneous Poisson point process, the variance of the number of points that fall in a large window is of the order of the window volume. In contrast, for hyperuniform (HU) point processes, the corresponding variance is much lower than the volume of that window, with a ratio going to zero.

Hyperuniform point processes have received a lot of attention in statistical physics, both for the investigation of natural organized structures and the synthesis of materials. There are many candidate HU processes in the physics literature, but rigorously proving that a point process is HU is usually difficult. It is thus desirable to have standardized numerical tests of hyperuniformity. A common practice in statistical physics and chemistry is to use a few samples to estimate a spectral measure called the structure factor, and evaluating its decay around zero provides a diagnostic of hyperuniformity. Different applied fields use however different estimators, and important algorithmic choices proceed from each field’s lore.

In an effort to make investigations of the structure factor and hyperuniformity systematic and reproducible, we further provide this Python toolbox gathering the estimators of the structure factor surveyed in [HGBLachiezeR22], along with a new statistical test of hyperuniformity asymptotically valid [HGBLachiezeR22], the test of effective hyperuniformity [Tor18] and the corresponding possible class of hyperuniformity [Cos21].

## Companion paper

We wrote a companion paper to `structure-factor`

,

where we provided rigorous mathematical derivations of the structure factor’s estimators of a stationary point process and showcased `structure-factor`

on different point processes.
We also contribute a new asymptotically valid statistical test of hyperuniformity.
Finally, we compared numerically the accuracy of the estimators.

If you use `structure-factor`

, please consider citing the companion paper.

## Installation

See the “Installation” section in the README file on GitHub.

## Getting started

Please refer to

the tutorial Jupyter notebook, and

the different sections of the present documentation.