Deepak Dhar and the 2026 Dirac Medal

Renowned Indian theoretical physicist Professor Deepak Dhar has been named a co-recipient of the 2026 Dirac Medal, awarded by the Abdus Salam International Centre for Theoretical Physics (ICTP) in Trieste, Italy. He has been recognised for his pioneering contributions to statistical physics, particularly his work on the Abelian Sandpile Model.

Dhar shares the award with Bernard Derrida, Marc Mézard and Haim Sompolinsky for their important contributions to statistical physics and non-equilibrium systems. He is the second scientist working in India to receive the Dirac Medal, after Ashoke Sen in 2014.

Abelian Sandpile Model

Concept and Development

Professor Deepak Dhar developed the Abelian Sandpile Model in 1990, building upon the concept of Self-Organized Criticality proposed in 1987 by Per Bak, Chao Tang and Kurt Wiesenfeld. The model explains how simple local interactions can produce complex and cascading behaviour in large systems.

In the model, sand grains are added one by one to a pile. As the pile approaches a critical state, the addition of another grain can trigger an avalanche, whose size may range from a small local event to a much larger cascade.

Abelian Property

The key contribution of Dhar was demonstrating the Abelian property, according to which the final stable configuration remains unchanged regardless of the order in which individual grains topple. This property makes it possible to mathematically analyse apparently unpredictable cascading processes.

Self-Organized Criticality

The model demonstrates Self-Organized Criticality, in which a system can naturally evolve towards a critical state. Once this state is reached, even a small disturbance can trigger events of widely different magnitudes. This provides an important framework for studying cascading behaviour in complex systems.

Applications

The concepts developed through the sandpile model have been used to understand cascading and complex behaviour in phenomena such as earthquakes, forest fires, traffic jams, neural activity and financial-market fluctuations.

Who is Professor Deepak Dhar?

Education and Academic Career

Professor Deepak Dhar was born in 1951 in Pratapgarh, Uttar Pradesh. He studied at Allahabad University, completed his master's degree at IIT Kanpur, and obtained his PhD from the California Institute of Technology (Caltech) in 1978.

During his doctoral studies at Caltech, Dhar worked as a teaching assistant to Nobel laureate Richard Feynman.

Major Awards and Recognition

Dhar received the Shanti Swarup Bhatnagar Prize in 1991, followed by the TWAS Prize in 2002 and the Padma Bhushan in 2023.

In 2022, he became the first Indian recipient of the Boltzmann Medal, the highest honour in statistical physics, sharing it with John Hopfield. With the Dirac Medal, Dhar belongs to a small group of scientists who have received both the Boltzmann Medal and the Dirac Medal.

Dirac Medal

About the Award

The Dirac Medal was instituted in 1985 by the Abdus Salam International Centre for Theoretical Physics (ICTP) in Trieste. It honours Paul A. M. Dirac, the renowned physicist and Nobel laureate who made foundational contributions to quantum mechanics.

The medal recognises scientists who have made outstanding contributions to theoretical physics and is announced annually on 8 August, the birthday of Paul Dirac.

About ICTP

The Abdus Salam International Centre for Theoretical Physics was founded in 1964 by Pakistani physicist and Nobel laureate Abdus Salam. It promotes international scientific cooperation, particularly by connecting scientists from the Global South with the wider international scientific community.

The ICTP operates under a tripartite agreement involving Italy, UNESCO and the International Atomic Energy Agency (IAEA).

Selection and Distinction

By tradition, the Dirac Medal is not awarded to individuals who have already received the Nobel Prize, Fields Medal or Wolf Prize, although some Dirac Medal recipients have subsequently received Nobel Prizes.