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Wednesday, November 11, 2015

Noval derivation of pi links quantum physics and pure math

"I find it fascinating that a purely mathematical formula from the 17th century characterises a physical system that was discovered 300 years later," said one of the lead researchers, Tamar Friedmann, a mathematician at the University of Rochester in the US. Seriously, wow.
The discovery was made when Carl Hagen, a particle physicist at the University of Rochester, was teaching a class on quantum mechanics and explaining to his students how to use a quantum mechanical technique known as the 'variation principle' to approximate the energy states of a hydrogen atom.
While comparing these values to conventional calculations, he noticed an unusual trend in the ratios. He asked Friedmann to help him work out this trend, and they quickly realised that it was actually a manifestation of the Wallis formula for pi – the first time it had even been derived from physics.
"We weren't looking for the Wallis formula for pi. It just fell into our laps," said Hagen. "It was a complete surprise," added Friedmann. "I jumped up and down when we got the Wallis formula out of equations for the hydrogen atom."
Since 1655 there have been plenty of proofs of Wallis's formula, but all have come from the world of mathematics, and the new results have people freaking out. The results have been published in the Journal of Mathematical Physics.
"In quantum mechanics, a technique called the variational approach can be used to approximate the energy states of quantum systems, like molecules, that can't be solved exactly. Hagen was teaching the technique to his students when he decided to apply it to a real-world object: the hydrogen atom. The hydrogen atom is actually one of the rare quantum mechanical systems whose energy levels can be solved exactly, but by applying the variational approach and then comparing the result to the exact solution, students could calculate the error in the approximation."

"That a formula for π is hidden inside the quantum mechanics of the hydrogen atom is surprising and delightful."