Unifying themes of complex systems
Taken from Introduction
to Complex Systems lecture by Tomaso Aste:
Complex systems
- exhibit emergence (some properties present at system level
are not present at lower level — e.g. a cell is alive but is made of
inanimate elements)
- are open (energy and information are constntly being imported
and exported acoss system boundaries)
- have a history (the history cannot be ignored, even a small
change in circumstances can lead to large deviations in the future)
- can adapt (in response to external or internal changes,
the system can reorganize itself without breaking — self organizing)
- are not completely predictable (when a system is adaptive,
unexpected behaviours can emerge — prediction becomes expectation)
- are multi-scale and hierarchical (system
size and structure scale are over several orders of magnitude and distinct
properties and functions are associated with different scales; dynamics can
propagate through scales — avalanches, cascade effects)
- are disordered (there is no compact and concise way to
encode the whole information contained in the system)
- have multiple (meta) (stable) states (small
perturbations lead to recovery, larger ones can lead to radical changes of
properties; dynamics do not average simply).
Note: these themes are also on the Summer
School Lecture Notes Wiki page.