Phase transition/Bifurcation/ Critical point

The change of context may induce a spontaneous qualitative change of the system making the previously stable state unstable. Sometimes context destabilizes. Close to such criticaltipping or bifurcation points a minuscule perturbation is sufficient to start the qualitative change. At the moment when the instability of the previously stable state occurs a process starts that enhances the initial change (perturbation). This process is called a positive feedback. Transitions between the solid, liquid, gaseous and plasma (ionized) states is maybe the most popular example. Avalanches are another example of this process. The magnetization and changes of social systems or war and rebellion onsets are yet further examples. In all these cases a very small physical or social perturbation is needed to unleash the positive feedback. Phase transitions last for a short time compared with the rate of change of the context. For example, the formation of new social order may take few months or years while the evolution of the context that brought about that change may last for tens or hundreds of years. In similar vein, the formation of grasping movement may take several hundreds of milliseconds while our approach to the glass to be grasped (i.e. change of the context) may take several seconds or more. During these quick processes there is an ever increasing rearrangement of components involved in the process. In avalanches it is the snow distribution, in magnetization it is the microscopic magnetic moments orientation and during the social changes it is the rearrangement of social stratums, attitudes and values. What happens in our neuro-muscular system during the initiation of each movement is an increasing activation (positive feedback) of neuro-muscular units in order to attain a suitable muscular force in order to overcome the limb inertia.

Depending on the context the positive feedback will turn into its opposite – the negative feedback. Negative feedback suppresses the initial change and returns the system into its stable state. It stops the increasing rearrangement of system’s components characteristic for the phase transition.  It is responsible for attaining and the degree of stability of the system. It suppresses any perturbation that threatens the extant stable behavior/structure. The generation of new state of matter, avalanches, social changes and biological motion stops when negative feedback stops the rearrangement of additional components that supported the process. For example, an individual or social (say institutional) behavior that is stable under some social context will quickly be re-established even if the state government initially ried by legislative to impose some other behavior. Negative feedback (recovering the stable state) is done by the collective (socialfield that corrects any individual component going ‘astray’ (peer pressure, conformity).

Robert Hristovski 12.05.2016