Matter of Memory

Coordinators: Sidney Nagel

Most of what we learn in physics classes concerns the properties of systems, such as an isolated container of gas or the magnetism of interacting spins, that are in thermal equilibrium. However, most of the world around us is far from equilibrium; we are at a loss as to how to understand such systems in terms of universal approaches, equivalent to the subject matter of thermodynamics or statistical mechanics. We cannot describe the weather – where constant energy input from the Sun keeps the Earth far from equilibrium – nor the properties of glassy materials – where thermal energy is insufficient to allow the atoms to explore phase space. The Universe, the largest far-from-equilibrium system that we know, is still recovering from the Big Bang. One of the frontiers of contemporary physics is to understand systems that are far from equilibrium. This is at the heart of understanding the world around us.

One obvious difference between systems that are in equilibrium from those that are not is in their ability to store a memory of how they were formed. The very process of reaching equilibrium erases all memories of previous training while a system that has not fully relaxed has the potential to retain memories of its creation. Thus the ability of a system to remember its genesis can only be found in systems that have not yet reached thermal equilibrium. But memory retention and memory loss are not simple processes – it can be done in a seemingly countless number of ways. What is memory formation? What makes different kinds of memories equivalent? A study of these questions can be an entree for understanding the nature of the non-equilibrium world.

Both in biology and in materials science, memory formation takes many forms. We are all familiar with the memories that are stored in the connections of neurons within our brains. Certain experiences are indelible even if experienced only once while others need many repetitions in order to be reliably recalled. It seems unlikely that we store “muscle memory” in our brains in the same fashion that we store our home address or cell-phone number. In the physical world, we are familiar with memories stored by pencil marks on a sheet of paper or with digitized information in a computer stored in the form of magnetic bits. Out-of-equilibrium systems may form memories by falling into a recognizable set of states in a vast, rugged energy landscape.

This Teachers’ Conference will look at what is common in these diverse systems, and will perhaps point the way forward towards novel ways for information to be encoded in matter and for understanding systems, so common in the world around us, that have not been allowed to reach bland equilibrium.

Talks at this full-day conference are scheduled to give ample time for questions and discussions from the audience, with talks typically about 40 minutes followed by an interaction period of 15-20 minutes. At the Friday evening reception and Saturday lunch, teachers gather with the speakers and other scientists for informal discussion. See our archive for descriptions and recorded talks from past teachers' conferences.


  • Irmgard Bischofberger (MIT)
  • Susan Coppersmith (University of Wisconsin)
  • Nathan Keim (Cal Poly, San Luis Obispo)
  • Arvind Murugan (University of Chicago)
  • Zorana Zeravcic (ESPCI Paris)

Lodging and logistical details