El universo está salpicado de galaxias que, a gran escala, exhiben un patrón filamentoso conocido como red cósmica. Esta distribución variopinta de material cósmico es, en cierto modo, como arándanos en un panecillo, donde el material se acumula en ciertas áreas pero puede faltar en otras.

Sobre la base de una serie de simulaciones, los investigadores comenzaron a probar la estructura heterogénea del universo, tratando la distribución de las galaxias como una colección de puntos, como las partículas individuales de materia que forman un material, en lugar de una distribución continua. Esta técnica permitió la aplicación de las matemáticas desarrolladas para la ciencia de materiales para cuantificar el desorden relativo del universo, permitiendo una mejor comprensión de su estructura fundamental.

Visualización de las estructuras más grandes del universo del Sloan Digital Sky Survey. Crédito: NASA/Universidad de Chicago y Adler Planetarium and Astronomy Museum

«Lo que encontramos fue que la distribución de las galaxias en el universo es bastante diferente de las propiedades físicas de los materiales convencionales, y tiene su propia firma única», explicó Oliver Philcox, coautor del estudio.

Este trabajo, ahora publicado en Examen físico Xfue realizado por Salvatore Torquato, miembro frecuente y visitante del Instituto de Estudios Avanzados y profesor Lewis Bernard de Ciencias Naturales con sede en[{» 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.

Esta visualización presenta una vista en 3D de las estructuras más grandes del universo. Comienza con datos del Sloan Digital Sky Survey y se aleja para revelar datos WMAP. Crédito:[{» 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