Une nouvelle perspective sur la structure de base de l’univers

L’univers est plein de galaxies qui, à grande échelle, présentent un motif filamenteux, appelé toile cosmique. Cette distribution hétérogène de la matière cosmique est à certains égards comme des myrtilles dans un gâteau où la matière s’accumule dans certaines zones mais peut manquer dans d’autres.

Sur la base d’une série de simulations, les chercheurs ont commencé à sonder la structure hétérogène de l’univers en traitant la distribution des galaxies comme des collections de points – comme des particules individuelles de matière qui composent la matière – plutôt que comme une distribution continue. Cette technique a permis d’appliquer les mathématiques développées pour la science des matériaux pour déterminer le désordre relatif de l’univers, permettant une meilleure compréhension de sa structure de base.

Une visualisation des plus grandes structures de l’univers du Sloan Digital Sky Survey. Crédit : NASA/Université de Chicago et Adler Planetarium and Astronomy Museum

« Ce que nous avons découvert, c’est que la distribution des galaxies dans l’univers est très différente des propriétés physiques des matériaux conventionnels, qui ont leur propre signature unique », a expliqué Oliver Vilkox, co-auteur de l’étude.

Ce travail est maintenant publié dans X examen physiqueSalvatore Torquato est membre et visiteur fréquent de l’Institute for Advanced Study et professeur Louis Bernard de sciences naturelles basé à[{ » attribute= » »>Princeton University’s departments of chemistry and physics; and Oliver Philcox a visiting Ph.D. student at the Institute from September 2020 to August 2022, now a Junior Fellow in the Simons Society of Fellows, hosted at Columbia University.

Cette visualisation fournit une vue 3D des plus grandes structures de l’univers. Il commence par les données de l’enquête Sloan Digital Sky et effectue un zoom arrière pour révéler les données de WMAP. crédit:[{ » attribute= » »>NASA/University of Chicago and Adler Planetarium and Astronomy Museum

The pair analyzed public simulation data generated by Princeton University and the Flatiron Institute. Each of the 1,000 simulations consists of a billion dark matter “particles,” whose clusters, formed by gravitational evolution, serve as a proxy for galaxies.

One of the main results of the paper concerns the correlations of pairs of galaxies that are topologically connected to one another by means of the pair-connectedness function. Based on this—and the array of other descriptors that arise in the theory of heterogeneous media—the research team showed that on the largest scales (on the order of several hundred megaparsecs), the universe approaches hyperuniformity, while on smaller scales (up to 10 megaparsecs) it becomes almost antihyperuniform and strongly inhomogeneous.

A section of the universe (black and white), with dark matter halos indicated by points and their associated large-scale topological structures indicated by colors. Credit: Philcox & Torquato; The Quijote Simulations

“The perceived shift between order and disorder depends largely on scale,” stated Torquato. “The pointillist technique of Georges Seurat in the painting A Sunday on La Grande Jatte (see image below) produces a similar visual effect; the work appears disordered when viewed up-close and highly ordered from afar. In terms of the universe, the degree of order and disorder is more subtle, as with a Rorschach inkblot test that can be interpreted in an infinite number of ways.”

“A Sunday on La Grande Jatte” by Georges Seurat.

Statistical tools, specifically nearest-neighbor distributions, clustering diagnostics, Poisson distributions, percolation thresholds, and the pair-connectedness function, allowed the researchers to develop a consistent and objective framework for measuring order. Therefore, their findings, while made in a cosmological context, translate to a number of other dynamical, physical systems.

This interdisciplinary work, combining the techniques of cosmology and condensed matter physics, has future implications for both fields. Beyond the distribution of galaxies, many other features of the universe can be explored with these tools, including cosmic voids and the ionized hydrogen bubbles that formed during the reionization phase of the universe. Conversely, the novel phenomena discovered about the universe may also provide insight into various material systems on Earth. The team recognizes that more work will be needed before these techniques can be applied to real data, but this work provides a strong proof-of-concept with significant potential.

Reference: “Disordered Heterogeneous Universe: Galaxy Distribution and Clustering across Length Scales” by Oliver H. E. Philcox and Salvatore Torquato, 14 March 2023, Physical Review X.
DOI: 10.1103/PhysRevX.13.011038