Why Complex Systems Change in Steps

Discussion

Robert Aunger:

"A general phenomenological theory of steady-state non-equilibrium thermodynamics has recently been developed to explain transitions in the degree to which a system exhibits energetic disequilibrium[24,25]. This theory has been formulated because the simplest kind of non-equilibrium condition is a non-equilibrium steady state. This approach is phenomenological because it develops theory in terms of measurable quantities, and thus facilitates empirical testing. In particular, steady states can be characterized by values of temperature, volume, the amount of matter, and energy flux (the free energy that passes through the system within a unit time). Steady states are thus local, temporally bounded systems. In a non-equilibrium steady-state, a constant flux of energy moves through the system. During periods of stability, historical systems engage in what can be called thermodynamic ‘work cycles’, or consistently repeating dynamic processes that maintain the system at a given degree of disequilibrium through the management of energy flows. For example, a proton – proton cycle fuels fusion reactions in the cores of some stars[, while animal metabolisms are fueled by the Krebs cycle. Work cycles maintain anon-equilibrium steady state which shows no macroscopically observable changes, while constantly exchanging energy with the environment. Since work cycles happen within a given organizational framework and do not significantly change the level of disequilibrium, exogenous shocks or accidental perturbations in the operation of a work cycle must arise to initiate a transition between steady-states. However, systems far from thermodynamic equilibrium can be subject to constant fluctuations in energy flow. The steady state may therefore become unstable and be replaced by another (or, perhaps, by a periodic or chaotic state). Small-scale divergences from a steady-state will often be accommodated; structural changes are caused only when some parameter exceeds a threshold value. For this reason, a steady-state will persist for some period before a structural change at the global level becomes necessary. Because they tend to be robustly controlled, complex systems tend to evolve in step-wise fashion[33,34].To move a system further from thermodynamic equilibrium, a perturbation must be due to an increase in energy flow through the system. This could either be the result of a random fluctuation or the input of anew source of energy. However, a random fluctuation will generally not lead to a sustained increase in energy flow. A significant transition is therefore more likely to start with a new kind or level of energy flow in a system, due to a new way of extracting energy from the system's surroundings.

This means that extracting energy will be called an ‘energy novelty’. As with a phase transition, the result of increased energy flow can be a new organisation of matter because, as energy flows through a system, physical structures can form."

(https://www.academia.edu/3007922/Major_transitions_in_big_history)