“…Since the introduction of the Wasserstein gradient flows in 1997-8 [26,27,40,42] it has become clear that a very large number of well-known parabolic partial differential equations and other evolutionary systems can be written as gradient flows. Examples of these are nonlinear drift-diffusion equations [2], diffusion-drift equations with non-local interactions [8], higher-order parabolic equations [41,22,25,32,23], moving-boundary problems [41,44], and chemical reactions [35]. The parallel development of rate-independent systems introduced similar variational structures for friction [18], delamination [29], plasticity [33], phase transformations [38], hysteresis [37], and various other phenomena.…”