Boltzmann Day 2025: Active matter and collective synchronization
May 6, 2025 | Bharti Dharapuram
The Boltzmann Medal, named after the Austrian theoretician Ludwig Botzmann, recognises exemplary contributions to the field of statistical physics.
The Boltzmann Day at IMSc celebrates the scientific achievements of Boltzmann Medal winners. This award recognises exemplary contributions to statistical physics and is conferred once in three years by the Statistical Physics Commission of the International Union of Pure and Applied Physics. It is named after Ludwig Boltzmann (1844-1906), an Austrian physicist and mathematician who laid the foundations of statistical mechanics by connecting macroscopic phenomena to the properties of atoms and molecules.
In the first edition of Boltzmann Day (28 June 2022), Deepak Dhar, a Emeritus Professor at IISER Pune, spoke about ‘The geometric phase transitions in a system of long rods on a lattice’, and John Hopfield, a Professor at Princeton University (winner of the 2024 Nobel Prize in Physics) presented a talk titled ‘Now what? Finding a problem’. This year’s Boltzmann Medal awardees are Yoshiki Kuramoto, an Emeritus Professor at Kyoto University, and Mehran Kardar, a Professor of Physics at the Massachusetts Institute of Technology. Kuramoto won the medal for his work on nonlinear oscillations, synchronization and weak turbulence, while Kardar won the medal for his contributions to non-equilibrium statistical physics.
In his talk ‘On the mathematical model of collective synchronization’ (22 April 2025), Kuramoto presented a retrospective on his namesake model–a mathematical framework to understand synchronization in several coupled oscillators. This phenomenon is common in nature, such as the beating of the heart, the collective flashing of fireflies, and the circadian clock. “Something mysterious happens with rhythms,” Kuramoto says, “they synchronize as if they recognise each other.” Building on the work of Arthur Winfree, Kuramoto proposed a tractable mathematical model to describe synchronization using a trigonometric coupling function. This was in contrast to earlier models, which used complex mathematics to describe the behaviour of even one or two oscillators. The Kuramoto model has been applied in various scientific disciplines, especially in the study of living systems.
Kardar’s talk on ‘Boundaries, inclusions and disorder in active matter’ (1 May 2025) described the non-equilibrium behaviour of active matter on interacting with the environment and its converse effects. The idea of active systems comes from biology where living entities are modeled as particles that interact with each other in a bounded environment. Kardar spoke about his work modeling interactions of active particles with each other, the bounding walls, and passive objects placed amongst them. He illustrated how these interactions can give rise to long-range correlations and persistent currents within active systems. He used useful analogies during his talk, describing the behaviour of a filament among active particles as “a sailboat in the middle of a lake”, and motility-induced phase separation as “a big jammed configuration of bumper cars.”
The winners will receive the Boltzmann medal during the 29th edition of the STATPHYS conference to be held in Florence from 13-18 July 2025. Having traveled across continents since 1949 (passing through India in 2004), the meeting returns to its inaugural venue this year.
