Complex systems

The overarching aim of the complex systems group is to increase our understanding of how complex behaviour can emerge in natural and artificial systems. The typical approach to these questions is to use quantitative or qualitative methods from one field and apply it to problems in another field, and thereby both make progress in the understanding of the latter and highlight fundamental similarities between the systems. The complex systems group consists of three senior researchers and their current research interests are briefly described below.

Information theory f​or complex system
Information theory provides a theoretical basis for describing and understanding phenomena ranging from emergent laws of physics, including the second law of thermodynamics, to emergent structures in, for example, chemical self-organizing systems. A current focus is on physical systems including both statistical mechanics and the process of quantum measurement.

The origins and evol​ution of humans and human societies.
Macroevolutionary theory of Major Evolutionary Transitions offer a radical new take on the origins and evolution of the genus Homo and her unique cumulative cultural societies. We are now in the phase of building up a collaboration with world-leading evolutionary biologists and anthropologists to explore the “social protocell model” and the hypothesized evolution of hominin communities into an organismic cultural organization, as an evolutionary individual in its own right. Parts of this work will focus on mathematical and simulation modeling of complex systems.
 
Stability of large c​omplex ecosystems
An ecosystem is a complex system consisting of many heterogeneous agents (species or individuals). The long and short term stability and robustness of these systems have been studied and discussed extensively in the literature for more than 50 years, but is still far from fully understood. A fundamental problem is how the complexity of the system, measured in terms of number of species or strength and topology of interactions among species affect its stability. Despite how important this is for understanding and predicting possible catastrophic biodiversity loss etc, this is still not well understood. The complex systems group has recently started a project that tries to address such  questions using dynamical systems theory. The work is done in collaboration with complex systems and theoretical biology group at UCLA in Los Angeles.

​Senior researchers: 
Martin Nilsson Jacobi, Kristian Lindgren, Claes Andersson, Karl-Erik Eriksson

Key publications:​
Kristian Lindgren, Eckehard Olbrich. The approach towards equilibrium in a reversible Ising dynamics model: An information-theoretic analysis based on an exact solution, Journal of Statistical Physics 168(4), 919-935 (2017).

Torbjørn Helvik and K. Lindgren. Expressing the Entropy of Lattice Systems as Sums of Conditional Entropies. Journal of Statistical Physics, (2014). (DOI 10.1007/s10955-014-0972-4).

Karl-Erik Eriksson, Kristian Lindgren. Giving quantum mechanics a chance, arXiv:1901.01035 [quant-ph] (2019).

Andersson, C., & Törnberg, P. (2019). Toward a Macroevolutionary Theory of Human Evolution: The Social Protocell. Biological Theory.

Andersson, C., & Read, D. (2016). The Evolution of Cultural Complexity: Not by the Treadmill Alone. Current Anthropology, 57(3), 261–286.

Andersson, C., & Törnberg, P. (2016). Fidelity and the Speed of the Treadmill - The Combined Impact of Population Size, Transmission Fidelity and Selection on Cultural Complexity. American Antiquity, 81(3).

Andersson, C., Törnberg, A., & Törnberg, P. (2014). An Evolutionary Developmental Approach to Cultural Evolution. Current Anthropology, 55(2), 154–174.

Andersson, C., Törnberg, A., & Törnberg, P. (2014). Societal systems: complex or worse? Futures, 63, 145–157. http://doi.org/10.1016/j.futures.2014.07.003​

Published: Wed 20 Mar 2019.