Criticality
202305231314
Status:
Tags: dynamical system
Tldr
A zone poised between complete order and disorder within a complex dynamical system at which certain signature properties are exhibited, such as a maximal repertoire of dynamic sub-states, fractal ‘self-similarity,’ or power-law scaling, and maximal sensitivity to perturbation (Bak1997).
Behavior exhibited when the ‘order parameter’ of the system undergoes a discontinuous phase transition as some other ambient property is modulated (Hesse2014)
Maximal sensitive to perturbation is a key feature of critical systems (Bak1997, Hesse2014, Tagliazucchi2016a)
Critical threshold between stability and chaos Girn2023
Complex systems tuned close to criticality exhibit computationally desirable properties
- increased adaptability and flexibility to inputs Shew2009 Shew2013
- increased encoding, storage, propagation of information ability Barnett2013
Signatures of criticality Cocchi2017:
- Scale-invariance (power-law statistics)
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- → parameters
- → events
- → critical exponent
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- Fractal/self-similar structure
- Presence of long-range correlations
- Strong sensitivity to external perturbations (‘critical slowing’)
Avalanche phenomena (Petermann2009)
Not always related to entropy, especially in the case of non-equilibrium systems. Given that some microstates are intrinsically more likely than others in the brain (e.g. more probable for a neuron to be active than quiescent (Beggs2012)), it may be the case that the brain is predisposed toward more ordered macrostates past the critical point (Shinozuka2023).