Seminar : Daan Frenkel (Department of Chemistry, University of Cambridge, UK)
Is there still life in entropy ?
Friday 12 March 2021 at 11am (online)
Abstract
Entropy is a well-known, but not necessarily well-understood concept. Initially introduced in the context of thermodynamics, it was given a microscopic interpretation by Boltzmann and Gibbs in the context of equilibrium statistical mechanics. But more recently, entropy like quantities have been introduced to describe non-equilibrium systems. For instance, in an attempt to construct a Statistical Mechanics of Powders, Sir Sam Edwards introduced the concept of « granular entropy », defined as the logarithm of the number of distinct packings of N granular particles in a fixed volume V. In 1989, the proposal was rather controversial but much of the debate was sterile because the granular entropy could not even be computed for systems as small as 20 particles – hardly a good approximation of the thermodynamic limit. In my talk I will describe how granular entropies of much larger systems can now be computed, using a novel algorithm. Interestingly, it turns out the definition of granular entropy will have to be modified to guarantee that granular entropy is extensive.
The techniques that we use to compute granular entropy may help us estimate the free energy of “equilibrated glasses”, if such things exist.
