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States and transitions in a simple model of a grassy path with park benches along it. The model has surprisingly rich memory behaviors, including learning, forgetting, and a stabilizing effect of noise.

We typically think of memory as the stuff stored in hard drives or our brains, but memory effects abound in a wide range of materials. Rubber and rocks can remember the largest load that was applied to them, glasses may remember a temperature where they were aged, and shape-memory alloys can recall a programmed shape. One approach to building a broader understanding of memory formation in matter is to construct and study simple models where memories may be written, stored, and retrieved. This article¬†shows how a model of worn grass between park benches can produce a peculiar memory behavior that has been observed in the motion of electrons in a special kind of conductor, and in the flow of solid grains in viscous liquids. Continue reading “How much can a grassy path remember?”