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Nima Arkani-Hamed

Harvard physicist seeks theory to unite relativity with quantum mechanics

Some people see beauty in art, others in music. Nima Arkani-Hamed (BSc 1993) sees beauty in the laws of physics. They have a “logical inevitability” that makes them instantly appealing, says the Harvard University physics professor.

The gold standard for “beauty” in physics was set by Albert Einstein, who proposed general relativity more than 80 years ago to explain how nature behaves at the scale of planets and galaxies. Einstein’s theory has stood the test of time, but physicists are now trying to figure out how to unite relativity with quantum mechanics, the set of laws that govern nature at the atomic scale.

Since the 1980s, most physicists have been placing their bets on string theory, which envisions a universe composed of tiny vibrating strings – along with unseen extra dimensions and perhaps even other universes beyond our own. Critics of this notion say these theoretical strings are so small – billions of times smaller than an atomic nucleus – that the theory can never be tested. But Arkani-Hamed and his Harvard colleagues have imagined a different scenario: the extra dimensions could be relatively large, maybe as big as a fraction of a millimetre. That’s large enough to allow string theory to be tested using particle accelerators (such as the much-anticipated Large Hadron Collider, now under construction near Geneva, Switzerland).

Arkani-Hamed is eager to see what experiments at the Large Hadron Collider reveal about the subatomic world – and even more anxious to find a theoretical framework that will embrace those discoveries. The new theory – whether it’s an offshoot of string theory or something different – would be subject to scientific scrutiny lasting decades. But Arkani-Hamed is confident that the right theory would demonstrate the “beauty” that characterized Einstein’s discovery. “I suspect if someone found the solution, we would all recognize 
it,” he says.

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