The story so far: Theoretical physicist Deepak Dhar has been awarded the Dirac Medal for his contributions to statistical physics — an honour he is sharing with three other physicists, Bernard Derrida, Marc Mézard, and Haim Sompolinsky. The Dirac Medal is awarded by the International Centre for Theoretical Physics (ICTP) in Trieste, Italy, on the birthday of the late British physicist Paul A.M. Dirac, for significant contributions to theoretical physics.
Key Factors
After finishing his doctorate, Dhar returned to India rather than stay in the U.S., and spent most of his career at the Tata Institute of Fundamental Research, Mumbai, before moving to the Indian Institute of Science Education and Research (IISER), Pune, in 2016. Because it captures a very general kind of behaviour: of systems that build up some kind of instability until they can release it in unpredictable ways, the Abelian sandpile model has numerous applications fundamentally. Scientists have used it to model earthquakes, the spread of forest fires, bursts of activity in neural networks in the brain, and fluctuations in financial markets.
What It Means
In the late 1980s, physicists Per Bak, Chao Tang, and Kurt Wiesenfeld proposed that this behaviour could be a general principle underlying many phenomena in nature, from earthquakes to forest fires to the extinction of species. They called it self-organised criticality. The term refers to a system that sometimes organises itself into a delicately balanced critical state where even small nudges can produce effects of any size, from trivial to significant.
