Subir Sachdev on AdS/CMT

Yes, it's the date of another major failed end of the world ;-)

My ex-colleague and fellow superhero, condensed matter physicist Subir Sachdev wrote a neat article for a mostly bad magazine called Scientific American,

Strange and Stringy

It does a good job in explaining one skill of string theory from a viewpoint of someone who was definitely not trained as a string theorist. In condensed matter physics, there are various phases of matter displaying numerous kinds of behavior (and critical behavior) and things can get very complicated. However, under somewhat general circumstances, when the complexity becomes really extreme, there is another, alternative description of the situation that becomes easy, at least once you know its formalism.




So like any proper solid state physicist, Sachdev doesn't care about the right theories at the Planck scale – or any other scale that is more fundamental than the characteristic scale of the phenomena in the common materials, for that matter. But even in this seemingly mundane realm that looks as non-fundamental as Radiohead, one may apply relationships that were found by physicists who analyzed a consistent description of quantum gravitational phenomena – who studied string theory in its familiar regime.

Sachdev makes some provoking points – e.g. that he had to explain basics of condensed matter physics to some string theorists using the same caricatures as he's using, approximately speaking, for the kids in the kindergarten. ;-)

I have some doubts whether the dual AdS-like description of condensed matter physics and related problems may ever be considered an "ultimate reliable description". But string theory surely gives us a new perspectives from which one may look at various physical situations and Subir Sachdev is among those who are exploiting these new opportunities very often.

Incidentally, Backreaction reviews some at least superficially clever attempts by Cliff Burgess and others to solve the cosmological constant problem within the large extra dimensions scenario. A cosmic string – or, more generally, a co-dimension-2 brane – induces a deficit angle in the surrounding spacetime but leaves the cosmic string essentially undisturbed. Such co-dimension-2 branes on a sphere may conspire to produce a rugby ball geometry which adjusts itself so that the effective 4D curvature seems to be (nearly?) zero.



Off-topic: For her 60th anniversary of reign, Queen Elizabeth received a chunk of Antarctica and a new rendition of the royal anthem (the video above).