In a Complex System, the interaction between the parts or sub-systems allows the emergence of global behaviour that would not be anticipated from the behaviour of components in isolation. This emergent behaviour depends upon the nature of the interactions as much as it does upon the character of the parts and changes when these interactions change.

Such systems are inherently non-linear and so may exhibit hysteretic or irreversible transitions between alternative states. They are frequently characterized by "fractal scaling laws" and may exhibit "self-organization".

Complex systems are being found and studied at a huge range of time and space scales from those of a single cell to the entire globe and involve processes ranging from physical or chemical alone to the intersection of biophysics and socio-economics.

The characteristic non-linearity of complex systems means that computer modeling and the concepts of dynamical systems theory play a major part in their study.

Some examples of Complex Systems Science where the application of these concepts and tools is leading to radically new results are:

• Biological Systems
  • Whole cell behaviour [1]; Biological signaling at the cell level [1];
  • Rhythmic processes in Physiology [2]
• Statistical and condensed matter physics
  • Critical point phenomena in materials including glass formation [3]
  • The behaviour of magnets and solid-liquid-gas transitions [1,3]
• Manufacturing Systems
  • Network design [1]
• Geophysics
  • Geodynamics and landscape formation [1,4]
  • Crustal fault systems dynamics and the earthquake prediction question; Formation of river and catchment systems[1,4,5]
• Earth System Science
  • Global Change-biophysical-social-economic interaction at global to regional scale [6,7]

other CSS sites

1. Gallagher, R. and Appenzeller, T. (1999) 'Complex Systems' Viewpoints Article (Gallagher, R. and Appenzeller, T eds.) Science 284, 79-109
2. Glass, L. (2001) Synchronization and Rhythmic processes in physiology. Nature 410: 277-284
3. Debenedetti, P. G. and Stillinger F.H. (2001) Supercooled liquids and the glass transition. Nature 410: 259-267
4. Ziemelis, K (2001) Complex systems-Nature Insight Review, Ziemelis Ed. Nature 410: 242-258
5. Bak, P. (1996) How Nature Works: The Science of Self organized Criticality .(Springer-Verlag, New York)
6. Holling, C.S. (2001) understanding the Complexity of Economic, Ecological and Social Systems. Ecosystems 4: 390-405
7. Scheffer, M., Carpenter, S., Foley, J.A., Folkes, C. and Walker, B. (2001) Catastrophic shifts in Ecosystems. Nature 413: 591-595.