A network dynamics approach to chemical reaction networks

A treatment of chemical reaction network theory is given from the perspective of nonlinear network dynamics, in particular of consensus dynamics. By starting from the complex-balanced assumption the reaction dynamics governed by mass action kinetics can be rewritten into a form which allows for a very simple derivation of a number of key results in chemical reaction network theory, and which directly relates to the thermodynamics and port-Hamiltonian formulation of the system. Central in this formulation is the definition of a balanced Laplacian matrix on the graph ofchemical complexes together with a resulting fundamental inequality. This immediately leads to the characterization of the set of equilibria and their stability. Furthermore, the assumption of complex-balancedness is revisited from the point of view of Kirchhoff’s Matrix Tree theorem. Both the form of the dynamics and the deduced behavior are very similar to consensus dynamics, and provide additional perspectives to the latter. Finally, using the classical idea of extending the graph of chemical complexes by a ‘zero’ complex, a complete steady-state stability analysis of mass action kinetics reaction networks with constant inflows and mass action kineticsoutflows is given, and a unified framework is provided for structure-preserving model reduction of this important class of open reaction networks