DOI
https://doi.org/10.1016/j.coche.2016.07.008

Summary
All non-equilibrium complex systems consist of element scales, system scales and mesoscales in between. The word mesoscale is not an absolute physical size, but a relative concept to describe phenomena and processes that manifest between element and system scales. Because of the inherent heterogeneity in these systems, conservation laws alone are not sufficient to define system behavior; stability conditions defined by variational criteria are necessary to correlate the parameters of different scales to define their steady states. Often, complex systems are governed by at least two dominant mechanisms. For instance, mechanism A and B. One mechanism drives the system to one state and the other mechanism forces the system to another state. Three possible regimes can be found. A regime dominated by mechanism A; a regime dominated by mechanism B, and a regime wherein both mechanism A and B coexist. Which regime dominates can be determined by using the Energy Minimization Multi-Scale (EMMS) model explained into this paper. The EMMS model requires the verification of two variational principles and it is alternative to non-equilibrium thermodynamics that uses a single general variational criterion. The latter criterion is either the minimization or the maximization of the entropy production rate.

Relevance for Complex Systems Knowledge
The EMMS model proposed in this paper wants to become an alternative method for making prediction of Complex Systems’ dynamics. In non-equilibrium thermodynamics, there exists the debate whether the variational principle is the minimum or the maximum of dissipation (usually referred to entropy production rate). Considering the EMMS principle, the authors declare that both variational criteria are both involved in shaping the structures of Complex Systems.

Point of Strength
It proposes an evolutionary criterion of Complex Systems, which is alternative to the traditional approach of non-equilibrium thermodynamics. It is deduced that searching a single variational criterion in term of entropy production (or dissipation) is right for either A- or B-dominated regime, but not likely in the A-B compromise regime due to multiple dissipative mechanisms with different extremum behaviors.