A brilliant Indian-American mathematician whose work has explored the shifting boundaries of probability was recently awarded one of the math world's highest honors.

Since 1963, Indian-born Srinivasa Varadhan has been teaching and conducting research at New York University's prestigious Courant Institute of Mathematical Sciences, in New York City. This past May, Varadhan won one of mathematics' top honors, the 900-thousand dollar Abel Prize, for his pioneering research in probability theory.

The Abel Prize, named for 19th century Norwegian mathematician Niels Henrik Abel, has been given annually by the Norwegian government since 2002 to honor the world's most influential mathematicians.

Varadhan says he feels lucky to have been selected. "Mathematics is a vast area and many people are doing research in many different areas of mathematics," he says, "and for your area to be chosen and for your contribution to be chosen in your area is a big surprise."

In tapping Varadhan for the Abel, the Prize committee cited his groundbreaking research in the theory of large deviations, a field that focuses on the probability that rare events will occur.

The simplest example of this is coin tossing. At any given moment, it's impossible to predict whether a coin toss will come up heads or tails. But the more his process is repeated, the easier it is to know what to expect. For example, if a coin is tossed 100 times the number of heads should be, roughly, the same as the number of tails. But even if it's highly improbable, Varadhan says you could get 100 heads. "So there's a difference in probability between what is probable, what's improbable, and what's impossible."

Varadhan notes that with his research he tries to understand how unlikely certain events really are. There are many levels of uncertainty, he explains, and it's important for some people to know what to expect. His research has applications in many different fields, like finance, population dynamics, and traffic engineering.

"There are various things in life where the chance of something happening is very small, but on the other hand, if it happens, the implications are enormous," says the mathematician. One way of guarding against such unfavorable events, he adds, is finding out exactly how small their probability is.

Varadhan's journey to the summit of the mathematics world began in Chennai, India, where he was born in 1940.

He started getting serious about a career in mathematics during his undergraduate years at Madras University. It was in Calcutta, India, where he'd gone to get his PhD in applied statistics, that Varadhan says the urgings of his peers helped steer him from the applied side to the theoretical side of probability.

He finished his PhD and Varadhan decided to come to the United States to pursue further research in probability theory at New York University's Courant Institute. He was eventually offered a permanent position there.

After his first year in New York, Varadhan married his present wife, Vasundra — also a professor at New York University. They had two sons, Gopal and Ashok. Tragically, Gopal was killed in the 9/11 terrorist attacks on the World Trade Center.

Family and culture have been very important to Varadhan. He says he and his family have maintained strong ties to their homeland, and go back to India as much as they can. He says that he and his wife have always been very comfortable there. "But I think my professional life has been much more interesting here than it would have been in India," he notes, adding "the diversity of activity is just great here."

Varadhan, whose nickname is Raghu, says one of the things he enjoys most is interacting with other mathematicians. "All my long career I've always worked closely with many, many colleagues," the mathematician says, "and that's been one of the great pleasures: discussing and working with somebody else."

He also enjoys learning about new research at seminars and conferences, because while attending these gatherings, he says, he will come across things that are completely surprising and that prompt him to say "Gee, I never thought of that, isn't that fantastic?"

Srinivasa Varadhan hopes his award will inspire more young people to take an interest in mathematics, and that it might encourage private and public institutions to support math education and research with more funding.

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