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Mumbai physicist who devised mathematical way to define Einstein prediction wins top prize

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Equations devised by Abhay Ashtekar are used to study complex phenomena, like the geometry of space time and collision of black holes.

Bengaluru: Physicist Abhay Ashtekar, who just won the Einstein Prize awarded by the American Physical Society (APS), the world’s second largest organisation of physicists, is best known for solving a problem in general relativity three decades ago.

In 1987, Ashtekar, a physicist at Penn State, then aged 38, came up with a mathematical way to define a prediction Albert Einstein had made decades before: That gravity is a manifestation of the geometry of space time in a body’s neighbourhood.

This representation of what is called ‘loop quantum gravity’ came to be called the ‘Ashtekar Variables’, and is an important component of Einstein’s general relativity today. The variables are now used to explain and predict gargantuan phenomena, such as the collision of black holes.

How language connects with science

The $10,000 Einstein Prize, which is awarded every two years for “numerous and seminal contributions to general relativity, including the theory of black holes, canonical quantum gravity, and quantum cosmology”, will be presented on 23 October.

“The prize is special,” Ashtekar told news agency IANS in an email interview, “because is it the highest honour bestowed by APS in the broad area of gravitational science.”

“The first Einstein Prize was awarded jointly to Peter Bergmann and John Wheeler, who introduced general relativity to American universities by creating research groups,” he added. “Perhaps because the first award often sets the tone, subsequent prizes have come to recognise ‘lifetime achievements’. So the news was deeply satisfying.”

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Ashtekar was born two years after India’s Independence, on 5 July, in Maharashtra. He grew up in Mumbai and studied in a Marathi-medium school until he turned 11. He then started studying in English and Hindi, realising that language ties in with cultures and beliefs, and, by extension, scientific understanding as well.

“What is considered great in one language or context could well be mediocre in another,” he added.

“At the same time, I learned Newton’s laws and universality of gravity — what makes the apple fall on Earth also makes the planets go around the Sun. This was stunning by itself,” he added.

In his early years, Ashtekar was particularly fascinated with cosmology, crediting George Gamow’s One Two Three… Infinity for sparking his interest in the subject.

His first academic exposure to physics came during his undergraduation studies, when he attended student meetings focussed on physics at the Tata Institute of Fundamental Research (TIFR), Mumbai. When he went to the United States immediately afterwards for his PhD, he wanted to work on gravity.

Just before going there, he wrote to the American physicist Richard Feynman, pointing out an error in one of the answers in his famous Feynman Lectures. Feynman wrote back, acknowledging the error, and this, Ashtekar believes, proved important in getting him admitted to the University of Texas.

In the US, Ashtekar started working with the big names in physics. He transferred to Chicago and finished his PhD at the University of Chicago, where he got to work with the likes of Nobel laureate Subrahmanyan Chandrasekhar (‘Chandra’) and Robert Geroch, his PhD supervisor.

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On Chandra’s suggestion, Ashtekar went to Oxford for his post-doctoral studies, and there he got to work with the English mathematical physicist Roger Penrose.

The subsequent years saw Ashtekar take up teaching assignment at the University of Paris, Syracuse University (New York, US), and finally at Penn State (Pennsylvania, US). He was awarded honorary degrees by the Friedrich-Schiller Universitaet, Jena, Germany, in 2005, and the Université de Aix-Marseille II, France, in 2010.

Of quantum gravity and clothing

He is most known for his work on loop quantum gravity, on which he’s been working for a quarter of a century.

The theory exists as an alternative to the string theory to explain the questions posed by general relativity. Most of this has to do with “quantising” the space-time curvature, that is, define it mathematically and restrict the amount of variables present in it.

It talks about how everything that is multidimensional is actually one-dimensional, stacked together to create a continuum. In an interview to The Wire, Ashtekar explained this by citing the example of a shirt.

“If I take this shirt, and I take a magnifying glass, I can see that the shirt is fundamentally one-dimensional, because the threads are one-dimensional. It’s just that those threads are so densely packed that I get an illusion that it’s two-dimensional,” he said.

“What comes out in loop quantum gravity is that the geometry of space is like that,” he added.

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“It’s woven by these one-dimensional fibres, it’s like a polymer. But this polymer is so intricately woven and tightly spaced that we get this illusion of continuum. It’s coarse-graining,” Ashtekar said.

“If you go to the atomic size, it’s not continuum at all. But if I coarse-grain it, there are so many atoms that, for all practical purposes, it’s a continuum.

“The same thing is true of geometry. The geometry we use in Einstein’s theory, general relativity, where space-time is a smooth continuum, is an approximation. To go beyond, one has to work with this fundamental building block, these atoms of space-time.

“That’s the basic idea of loop quantum gravity. Then one has to come up with proper equations for this.”

Ashtekar looks for these building blocks in the form of bits of signal in the cosmic background radiation, the dull omnipresent radio waves all around us that are the relic of the Big Bang.

Ashtekar’s first-ever award came in 1977, in the form of the Gravity Prize, handed out by the Gravity Research Foundation. He has also held and continues to hold several distinguished positions, such as Elected Foreign Fellow at the National Academy of Sciences (1997), Sir C.V. Raman Chair of the Indian Academy of Sciences (2004-2005), and chair, International Advisory Committee, the Indian Initiative in Gravitational-wave Observations (IndIGO), and LIGO-India (2010-present).

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  1. But we are all interested in the applicationext part.I believe he would have shared his views with his IINC Mukunda.Has he given his opinion on Tachions of Sudharshan.Has he felt anything about the cheating and thieving something out of him and yet he warms denied if a Nobel prize he was wouneed at heart.That us why I wrote to honourable Modhiji’s to have our own Nobel prize

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