Complex Systems

What complexity science is, and why…. is not only a question in a constant search for an answer but also the title of a recent, entertaining short essay by Petter Holme.  Holme is also the Editor of one the very first books on temporal networks that have gathered by now over 300 citations and 65k downloads and we would like to take the opportunity to express our congratulation to the editors and authors of this very popular introductory volume.  Let us also refer the interested reader to his recent article in EPJ Data Science on Susceptible-infected-spreading-based network embedding in static and temporal networks.

One feature of complex systems often referred to in the media these days, typically in the context of climate change, are the so-called tipping points as a measure of their ability to suddenly transition between drastically different patterns of behaviour. “Tipping” is generally triggered by small changes in the parameters of individual systems – whose effects can rapidly cascade to alter entire networks of interacting subsystems.  An exhaustive overview of the mechanisms and relevance of tipping pervading many different areas of modern research - from climate change, ecology, and seismology to socioeconomic areas, including psychology, social networks, and financial markets – is given in a recent special issue of EPJ Special Topics. 

A companion special issue, again in EPJ ST, explores more thoroughly dynamical phenomena in complex networks. Among the many highlights presented in this collection, let us mention various novel or improved methods for dealing with noise and stochastic processes in neuroscience, for constructing weighted networks with arbitrary topologies from a single dynamical node with delayed feedback, for generalizing the concept of geodesic distances, for formulating a path-integral formulation of network-based measures and for gaining fundamental insights into the dynamics of disease transmission.

Complex systems are also often associated with so-called rare events, often quite generically as part of long-tailed statistical distributions but also being specifically characterized as transitions between metastable states in phase space that require the system to overcome sizeable free energy barriers. In the recently published paper Reaction coordinates in complex systems - a perspective, the sampling and analysis of rare events in molecular simulations, an indispensable tool in the study of dynamical processes on the atomistic level, is carefully investigated.

The last paper we would like to feature in this short introduction combines complexity, here urban infrastructure complexity, with its close cousin, data science.  In a recent study on assessing biking safety in cities the authors utilize bike accident data from different cities to model the biking safety based on geographical and infrastructural street-level features. 

More highlights in complexity science from across the wider Springer Nature portfolio can be found in the articles and collections linked below.

The EPJ Publishing Editors