Since 1994 he has been a professor of mathematics and was the first person to hold the Mina Rees Chair in mathematics at the Graduate Center Faculty at The City University of New York.
Since 1994 he has been a professor of mathematics in the United States. He was a professor at Johns Hopkins University until 2002 when he became the first person to hold the Mina Rees Chair in mathematics at the Graduate Center Faculty at The City University of New York.