Srinivasa S. R. Varadhan, of New York University's Courant Institute of Mathematical Sciences, has been awarded the 2007 Abel Prize in mathematics by the Norwegian Academy of Science and Letters. Prof. Varadhan will receive the Abel Prize from King Harald V of Norway, in Oslo, on May 22. The honor is accompanied by a prize of approximately $920,000.
In awarding the annual prize, which Norway established in 2002, the Academy cited Prof. Varadhan's exceptional work on probability theory. It singled out Varadhan's development of the theory of large deviations because it "provides a unifying and efficient method for clarifying a rich variety of phenomena arising in complex stochastic systems."
The law of large numbers shows that the average outcome of a long sequence of coin tosses is usually close to the expected value. However, the unexpected does happen. The theory of large deviations concerns the occurrence of such rare events. So, even though in the long term, the probability of a rare event diminishes to zero, the rate at which it does so is important in practical applications. Prof. Varadhan discovered the underlying general principles that govern estimates of large deviations.
Varadhan's pioneering approach to large deviations has applications in fields as diverse as quantum field theory, statistical physics, population dynamics, econometrics and finance, and traffic engineering. Further, the Academy noted that Varadhan's mathematical research has "greatly expanded our ability to use computers to simulate and analyze the occurrence of rare events." Over the last four decades, the theory of large deviations has become a cornerstone of modern probability, both pure and applied.
The Academy also cited Varadhan's work with Daniel Stroock on the development of a martingale method for characterizing diffusion processes, and his work with Maozheng Guo and George Papanicolaou on gradient models, work that Prof. Varadhan eventually extended to handle non-gradient models. Additional information about his work can be found at http://www.abelprisen.no/nedlastning/2007/varadhan_en.pdf.
Prof. Varadhan was born in Madras (Chennai), India. He received his B.Sc. degree in 1959 and his Ph.D. from the Indian Statistical Institute, in Calcutta, in 1963. He has been at the Courant Institute since 1963.
Prof. Varadhan is a member of the National Academy of Sciences, the American Academy of Arts and Sciences, the Royal Society and the Third World Academy of Sciences. He has received numerous awards and honors, including the AMS-SIAM Birkhoff Prize (1994) and the AMS's Leroy Steele Prize (1996). He has received Alfred P. Sloan and Guggenheim Fellowships and is a fellow of the Institute of Mathematical Statistics and the Indian Academy of Sciences.—H. Waldman