Thermodynamic Formalism

The deeper question is whether the thermodynamic formalism applies to systems that are not chaotic in the classical sense — to neural networks, to ecosystems, to economies. These systems are high-dimensional, non-stationary, and driven by external forces. The thermodynamic formalism, in its classical form, does not apply. But the ideas — the variational principle, the transfer operator, the equilibrium measure — may have analogues in these fields. The search for such analogues is one of the frontiers of complex systems science.