On the complexity and the information content of cosmic structures

TL;DR

This paper introduces a novel information-theoretic method to quantify the complexity of cosmic structures, revealing where and how complexity emerges in galaxy clusters through analysis of cosmological simulations.

Contribution

It proposes a new quantitative approach based on Information Theory to measure the complexity and information content of cosmic structures from simulation data.

Findings

Highest complexity in cluster peripheries with shocks and energy fluctuations

Magnetic energy evolution requires twice as many bits to describe

Including cooling and feedback doubles the overall complexity

Abstract

The emergence of cosmic structure is commonly considered one of the most complex phenomena in Nature. However, this complexity has never been defined nor measured in a quantitative and objective way. In this work we propose a method to measure the information content of cosmic structure and to quantify the complexity that emerges from it, based on Information Theory. The emergence of complex evolutionary patterns is studied with a statistical symbolic analysis of the datastream produced by state-of-the-art cosmological simulations of forming galaxy clusters. This powerful approach allows us to measure how many bits of information are necessary to predict the evolution of energy fields in a statistical way, and it offers a simple way to quantify when, where and how the cosmic gas behaves in complex ways. The most complex behaviors are found in the peripheral regions of galaxy clusters, where supersonic flows drive shocks and large energy fluctuations over a few tens of million years. Describing the evolution of magnetic energy requires at least a twice as large amount of bits than for the other energy fields. When radiative cooling and feedback from galaxy formation are considered, the cosmic gas is overall found to double its degree of complexity. In the future, Cosmic Information Theory can significantly increase our understanding of the emergence of cosmic structure as it represents an innovative framework to design and analyze complex simulations of the Universe in a simple, yet powerful way.