Examples and applications
Benefits of criticality
Tutorial program and files

Self-organized criticality

Self-organized criticality

There has been a long history of attempts to propose physical theories to explain a seemingly heterogeneous variety of phenomena by a few general principles. Self-organized criticality (SOC) is certainly a prominent example of a theory with such a unifying purpose. It was proposed to explain the emergence of complexity.

The term ``self-organized criticality'' emphasizes two aspects of the system behavior. Self-organization is used to describe the ability of certain nonequilibrium systems in the absence of control or manipulation by an external agent to develop specific structures and patterns. The word criticality is used in order to emphasize the similarity with phase transitions: a system stays at the border of stability and chaos. The concept was coined by Bak et al. [1] who proposed the first SOC model and discovered the connection between SOC and the appearance of the power-law distributions.

Self-organized criticality has been used to model phenomena as diverse as the piling of granular media [11], plate tectonics [12], forest fires [21], stick-slip motion [10], and electric power system blackouts [6]. It has also recently become appealing to biologists [4,5] .

Critical behavior has been shown to bring about optimal computational capabilities [16], optimal information transmission [4], storage of information [13], and sensitivity to sensory stimuli [7,9,15].

It is without doubt that SOC is an important tool to understand more about appearance of power-laws and the phenomena of self-organization. Even if it should not be considered as a complete description of every phenomenon, it is still an important first step in comprehending complexity.

Anna Levina and J. Michael Herrmann