Deepak Dhar’s CV just got a new addition to what is already a very impressive list. The 74-year-old Indian theoretical physicist is a recipient of the 2026 Dirac Medal, which is considered one of the most illustrious awards in the realm of theoretical physics, conferred by the International Centre for Theoretical Physics (ICTP), Italy. Deepak Dhar is not the sole recipient of the award, which he won along with three other physicists: Bernard Derrida, Marc Mézard, and Haim Sompolinsky. All four were honoured for their efforts at transforming concepts from statistical mechanics, which is the area of physics concerned with collective behaviour of a large number of particles, into applications across diverse scientific fields.
Also read: Sovereign infra and sovereign AI not the same, says Tata Communications’ Andrew Winney
Dhar’s most important contributions were his rigorous studies of the Abelian sandpile model, a mathematically tractable version of self-organised criticality. The original sandpile model was introduced by Per Bak, Chao Tang and Kurt Wiesenfeld in 1987; Dhar later showed that its toppling operations have an Abelian or commutative structure. This means that, once an avalanche has ended, the final stable configuration does not depend on the order in which individual sites topple. His work also made it possible to calculate important properties of the model exactly.
In the model, grains are added one at a time to a pile or to sites on a lattice. Most additions cause no avalanche or only a small one, but some can produce cascades involving many sites. The crucial insight of self-organised criticality is that a system can naturally evolve towards a critical state without requiring the precise external tuning of a control parameter. The size of any particular avalanche remains unpredictable, although the statistical distribution of avalanches can be studied mathematically.
This work provided an exactly solvable framework for studying how simple local rules can generate complex collective behaviour. Related ideas have been explored in models of earthquakes, biological systems, traffic and financial-market fluctuations, but the sandpile model should not be presented as a universal explanation for earthquakes, forest fires, market crashes or brain activity. The relevance of self-organised-criticality models differs from one real-world system to another.
Also read: AAA open-world games are losing their charm: What went wrong along the way
The Dirac Medal, instituted in 1985 in memory of Nobel laureate Paul A.M. Dirac, is handed out annually on Dirac’s birthday, August 8, and has built a reputation as a genuine bellwether for future scientific greatness. Eight past Dirac medallists have gone on to win actual Nobel Prizes in Physics.
The first medal ever awarded was to Edward Witten and Yakov Zeldovich, the only physicist to win the prestigious Fields Medal – the highest honour in mathematics – and a leading player in the field of string theory. Some of the other notable recipients of the medal have included Leonard Susskind, the co-founder of string theory and holography, and John Hopfield, whose research in neural networks earned him the Nobel Prize in Physics in 2024.
Dhar’s credentials certainly make for a good case study in the form of his Ph.D. from Caltech, his decades-long association with Tata Institute of Fundamental Research, Mumbai, followed by time at IISER Pune, the 2022 Boltzmann Medal (being the first Indian to win the prestigious award in statistical physics), and finally the Padma Bhushan, one of the country’s highest civilian honours, in 2023.
The addition of the Dirac Medal to his list is bound to cement Dhar’s status as one of the most decorated physicists of modern-day India.