Thursday, October 20, 2011

Strange Bedfellows - String Theory and Condensed Matter Physics?

We have heard of this. Some aspects of the mathematics of string theory somehow have analogous form in other fields, such as condensed matter physics.

This Nature article (link may be open for free only for a limited time) explores how concepts in String Theory are now being explored in other fields, and whether this is a symbiotic relationship between them.

Sceptics still question whether this strange alliance will actually lead to new insights, or whether it is just a marriage of convenience. String theory does hint at the existence of many new states of matter, for example. But those predictions will be difficult to verify, and decisive experimental tests are only now in the planning stages.
The condensed-matter partnership seemed perfect for that. If nothing else, it promised to make a virtue out of string theory's embarrassment of riches — the roughly 10500 solutions to its basic equations, each of which describes a possible universe with its own size, shape, dimensionality and physical laws. Through Maldacena's idea, says string theorist Jerome Gauntlett at Imperial College London, "each solution can be expressed in the countless materials yet to be discovered".

The rewards are mutual, says Zaanen. "If I talk about superconductors and black holes in a colloquium, folk are attracted to it like bees to honey," he says. "It's now bringing young blood to condensed-matter physics, as their first choice."
Just as with the fictional odd couple, however, this partnership still has plenty of friction. Everyone agrees, for example, that condensed-matter physicists are much more hesitant about pairing up than their string-theory counterparts. "I have been remarkably unsuccessful at getting condensed-matter physicists to let string theorists speak at their big meetings," says Zaanen. "They fear that they will need to learn string theory to talk to them. It's as though I am asking them to have coffee with aliens."

Polchinski admits that the condensed-matter sceptics have a point. "I don't think that string theorists have yet come up with anything that condensed-matter theorists don't already know," he says. The quantitative results tend to be re-derivations of answers that condensed-matter theorists had already calculated using more mundane methods.
I suppose only time will tell if these collaborations will amount to anything. There are certainly hints at systems in condensed matter that can exhibit such rich variety of physics, such as topological insulators. Whether insights from String Theory can be beneficial remain to be seen.

Still, I don't think any of these "applications" of String theory actually validates the theory in itself. As the end of the article stated, String theory could be the "new calculus", but this is simply indicating that String theory is nothing more than a "tool", the way mathematics is, and not physics.


1 comment:

graphity said...

Hello, a minor quibble. Such fantastic systems as the topological insulators are out of the reach of AdS/CFT approach. As CFT implies criticality or gaplessness, the correspondence cannot handle insulators which are gapped.

Also, as discussed in the Review of Sachdev, the main application of AdS/CFT are conformal-matters (systems at criticality) and comperssible matters (with gapless excitations).