Tuesday, September 7, 2010

A test of String Theory via Quantum Entanglement?

A new study in Physical Review Letters, as described in an Imperial College London News Release claims that Researchers discover how to conduct first test of ‘untestable’ string theory. The press release states that
String theory was originally developed to describe the fundamental particles and forces that make up our universe. The new research, led by a team from Imperial College London, describes the unexpected discovery that string theory also seems to predict the behaviour of entangled quantum particles. As this prediction can be tested in the laboratory, researchers can now test string theory.

What the authors noticed was a relationship between the mathematical formulation of entangled quantum particles and black holes. Since the mathematical formulas for black holes are derived from string theory, they decided to take a closer look:
Professor Duff recalled sitting in a conference in Tasmania where a colleague was presenting the mathematical formulae that describe quantum entanglement: “I suddenly recognised his formulae as similar to some I had developed a few years earlier while using string theory to describe black holes. When I returned to the UK I checked my notebooks and confirmed that the maths from these very different areas was indeed identical.”

But what does this really mean?

Lisa Grossman has a good writeup in Wired: String Theory Finally Does Something Useful. The bottom line:
A chorus of supporters and critics, including Nobel laureate and string theory skeptic Sheldon Glashow and string theorists John Schwarz of Caltech, James Gates of the University of Maryland, and Juan Maldacena and Edward Witten of the Institute for Advanced Study in Princeton agree that Duff’s argument is “not a way to test string theory” and has nothing to do with a theory of everything.

Mathematician Peter Woit of Columbia University, author of the blog Not Even Wrong, thinks even claiming that the new paper is a test of quantum entanglement is going too far.

“Honestly, I think this is completely outrageous,” he said. Even if the math is the same, he says, testing the quantum entangled system would only tell you how well you understand the math.

“The fact that the same mathematical structure appears in a quantum mechanical problem and some model of black holes isn’t even slightly surprising,” he said. “It doesn’t mean that one is a test of the other.”

At Peter Woit's blog Not Even Wrong, he expounds on this:
I have no idea how this paper is supposed to contain a “test” of string theory. The simple quantum mechanics problem at issue comes down to classifying orbits of a group action on a four-fold tensor product, exactly what Wallach worked out in detail in his notes, as an example of Kostant-Rallis. If you do an experiment based on this and it doesn’t work, you’re not going to falsify string theory (or Kostant-Rallis for that matter).

It appears, at least preliminarily, that this isn't a test of string theory after all.

You can find a pre-print arXiv version of the research here.

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