APS Medal for Exceptional Achievement in Research Winner: Sidney NagelNature does not favor order; biology does not favor equilibrium

Disordered and far-from-equilibrium systems challenge our understanding; they appear ubiquitously and their study transcends any single discipline. What are questions for a physicist to ask which, if answered, would bring coherence and insight about this state of nature? There are many aspects on which one could concentrate, but one possibility is to recognize that during the approach to thermal equilibrium there is a transient period in which many characteristic features can be found. The ability of matter to store memories, of both its initial conditions and how it was manipulated and trained, is one aspect that I find particularly fascinating. Such memories cannot exist if the material is perfectly ordered or if it has fully reached equilibrium; thus, in some ways, memory is characteristic of this transient behavior. If we are lucky, it might even provide a way of distinguishing between different types of disorder and different forms of far-from-equilibrium behavior. Memories can be stored in a myriad of different ways and so it is a rich subject with a wealth of examples. In this talk, I will try to emphasize some ways in which memory formation can be a unifying concept.