Snow avalanche with powder cloud, Caucuses (Photo: med_ved/iStock)

Complexity scientists have long grappled with how to mathematically describe large numbers of interacting agents. One powerful technique for understanding complex systems has been statistical mechanics, which was originally developed to describe molecules interacting within gasses. In the past few decades, statistical mechanics has expanded from simple systems at thermal equilibrium (for example, a gas at room temperature) to considerably more complex systems at quasi-stationary states out of thermal equilibrium, such as those emerging in living organisms, adaptive structures, languages, stock exchanges, earthquakes, astrophysics, among many others.

In a special themed issue of the journal Entropy, Andrea Rapisarda (INFN Sezione di Catania) and SFI External Professors Stefan Thurner (Complexity Science Hub Vienna) and Constantino Tsallis (Centro Brasileiro de Pesquisas Físicas) have gathered together "new developments and original applications of generalized statistical mechanics to complex systems of various natures.” The issue consists of nine research papers, one review article, and an editorial that surveys the applications presented within the issue.

Read the full issue, “Nonadditive Entropies and Complex Systems” in Entropy (May 27, 2019)