Tuesday, January 01, 2008

Witten on "brane analog"

A few days ago Nature Physics published a letter by Bradley et. al. at Lancaster University on a supposed "brane analog" in low-temperature He3 physics:
In cosmological 'braneworld' models, our Universe exists on a brane embedded in higher-dimensional space. It's hard to test this theory, but there may be a laboratory analogue in helium-3 to probe brane-antibrane collisions — collisions that could have led to the Big Bang.
Here's the University's press release, which boldly begins:
Low-temperature physicists at Lancaster University may have found a laboratory test of the "untestable" string theory.
Peter Woit was skeptical, and notes how the UK press typically hyped the story -- here's the Telegraph, which makes the finding sound definite:
A "universe in a test tube" that could be used to assess theories of everything has been created by physicists.
And then it goes on and on about extra-dimensions and p-branes and all that.

So I thought I'd ask Edward Witten, one of the predominant string theorists in the world, and sure enough here's what he told me:
There is definitely no test of string theory here.
He goes on to say,
However, if one sets the bar a little lower, there is something that is interesting. Nature has a remarkable way of generating similar structures at different length scales, so the occurrence of various kinds of string and other topological defects in superconductors, liquid helium, etc. is a possible hint that nature likes such things at a much smaller length scale.


John Fleck said...

There was an amusing ambiguity in Witten's quote: "Nature has a remarkable way of generating similar structures." I at first glance read "Nature" there to mean the magazine, and immediately headed off on a tangent involving the remarkable ability of Nature (the magazine) to generate similar structures involving hyped news media coverage. :-)

MT said...

Are you thinking like a scientist or a reporter on this one? Even if an experiment only warms the hearts of people on one side of a theoretical debate, it could be worth talking about--if truly dispositive evidence has been and foreseeably will remain scarce, and there's an eager audience for news on the subject. I suppose there isn't much grounds for the weather forecast somedays.