For the last three months, Robert Langlands—the man behind the Langlands Programme, a pathbreaker in 20th Century mathematics—has wandered through the Tata Institute of Fundamental Research in Mumbai. The campus, he says, is “surprisingly good for interesting conversations” though none would speak to him in Hindi, which he wants to learn.

This trimester in India stirs Langlands’ memories of a search he had put off for over two decades — to find his missing letters to a friend and colleague of 20 years at Princeton’s Institute of Advanced Studies, where he is a professor.

The man was Harish-Chandra, one of India’s premier mathematicians —known for his work on representations of semi-simple Lie Algebras and groups — who, Langlands recalls, also neglected his Hindi.

“Perhaps the time has come to find the letters,” says Langlands. “I should find out if they are sitting in some attic, barn or basement at the Institute. I’m also going to ask his widow Lalitha, whom I knew in the US”. They call her “Lily”.

His years with Harish-Chandra—who once studied physics but left his mark in the Representation Theory at the Institute—were long ago, in the sixties. But in retrospect, Langlands thinks this “intense, tenacious” friend was ahead of his time, a man who understood Langland’s solutions at “decisive” moments in his career, when others were flummoxed or sceptical.

“I think India’s mathematicians in the sixties and seventies had a real presence in the world, everyone knew their names. I fear that’s no longer the case,” says Langlands, whose vast mathematical work connects geometry, number theory, analysis and the Representation Theory, in many ways. “There are more Indians abroad but their presence internationally is less than it was. I can’t tell why”.

... contd.