Associate Professor
School of Mathematics
University of Bristol, U.K.
What is a complex system?
This question is still not fully answered. Complex systems consist of many elements with many interactions between them. Their macroscopic behaviour is largely unpredictable from the elements alone because of feedback and noise. Many of the most profound and important theoretical and practical questions in science, medicine and society are now addressed with the ideas and methods of complexity science.
Entropy landscape of stem cells
The metaphor of a potential epigenetic differentiation landscape  suggests that during differentiation a stem cell follows the steepest descending gradient toward a stable equilibrium state which represents the final cell type. It has been conjectured that there is an analogy to the concept of entropy in statistical mechanics. In order to assess these predictions, we computed the Shannon entropy single-cell gene expression data. We find that the Shannon entropy is not decreasing but instead it increases toward the point of commitment before decreasing again. This indicates the importance of noise in cellular development.

Complex systems perspective on democracy

The idea that democracy is under threat, after being largely dormant for at least 40 years, is looming increasingly large in public discourse. Complex systems theory offers a range of powerful new tools to analyse the stability of social institutions in general, and democracy in particular. What makes a democracy stable? And which processes potentially lead to instability of a democratic system? This paper offers a complex systems perspective on this question, informed by areas of the mathematical, natural, and social sciences. We explain the meaning of the term 'stability' in different disciplines and discuss how laws, rules, and regulations, but also norms, conventions, and expectations are decisive for the stability of a social institution such as democracy.
Special Issue 'Information Theory in Complex Systems'
Submit until March 2019
I am co-directing the Bristol Centre for Complexity Sciences.
I am external faculty at the Complexity Science Hub Vienna.
I am affiliated member of the Centre for Science and Philosophy.
Image by Seila Fernández Arconada.