Anomalous thermal relaxation in physical systems and the Mpemba effect

The dynamics of rapid cooling or heating systems are full of surprising effects, where the thermal relaxation is counterintuitive or anomalous. A prime example of anomalous thermal relaxation is the Mpemba effect. The phenomenon is colloquially known as when "hot cools down faster than cold." More precisely, it is when a system prepared at a hot temperature overtakes a warm system in thermal relaxation and equilibrates to the cold environment faster. Comparing two identical physical systems in their relaxation to the environment, we'd expect that the system with a smaller mismatch between its and the environment's temperature will thermalize faster -- yet it is not always the case. The effect was observed in water, magnetic systems, clathrate hydrates, polymers, and colloidal particle systems. It was simulated in granular fluids, spin-glasses, driven gasses, quantum systems, magnetic alloys, and gases without equipartition. The numerous occurrences of the effect imply that it is general. My talk will overview the subject and present general theoretical results on the Mpemba effect on model systems, such as the overdamped Langevin dynamics, mean-field antiferromagnets, random energy models, and chemical reactions. I will link the Mpemba effect's occurrence with the physical system's properties, such as the shape of the potential in the Langevin dynamics or the characteristics of its metastable states. I will also discuss the impact of the Mpemba effect on thermodynamical cycle efficiency, systems memory, and optimal heating/cooling protocols. Finally, I will provide further insight into when such anomalous relaxation processes are expected and suggest potential applications of the Mpemba effect.

Place: Hybrid: Math, 501 and Zoom     Password:   Locute


2 p.m. Feb. 4, 2022


Hybrid; Math 501/Online