Friday, February 11, 2011

String theory and nanotechnology meet today in arxiv

String theory deal mainly with physic at the planck scale, although it's goal is to connect to with the electroweak scale.

On the other hand, nonotehcnology, deals with physics at sizes similar to the Bohr radius. There are, consequently, many orders of magnitude of difference among that two branches of physics.

Because of that it is absolutely amazing to see in the title of the paper a reference to a relation among them. But today in arxiv we have such a paper: Fermionic condensate and Casimir densities in the presence of compact dimensions with applications to nanotubes.

The abstract reads like this:

We investigate the fermionic condensate and the vacuum expectation value of the energy-momentum tensor for a massive fermionic field in the geometry of two parallel plate on the background of Minkowski spacetime with an arbitrary number of toroidally compactified spatial dimensions, in the presence of a constant gauge field. Bag boundary conditions are imposed on the plates and periodicity conditions with arbitrary phases are considered along the compact dimensions. The boundary induced parts in the fermionic condensate and the vacuum energy density are negative, with independence of the phases in the periodicity conditions and of the value of the gauge potential. Interaction forces between the plates are thus always attractive. However, in physical situations where the quantum field is confined to the region between the plates, the pure topological part contributes as well, and then the resulting force can be either attractive or repulsive, depending on the specific phases encoded in the periodicity conditions along the compact dimensions, and on the gauge potential, too. Applications of the general formulas to cylindrical carbon nanotubes are considered, within the framework of a Dirac-like theory for the electronic states in graphene. In the absence of a magnetic flux, the energy density for semiconducting nanotubes is always negative. For metallic nanotubes the energy density is positive for long tubes and negative for short ones. The resulting Casimir forces acting on the edges of the nanotube are attractive for short tubes with independence of the tube chirality. The sign of the force for long nanotubes can be controlled by tuning the magnetic flux. This opens the way to the design of efficient actuators driven by the Casimir force at the nanoscale.

I haven't read in deep the paper, but in a superficial reading I have got a confirmation that they are actually claiming that actual aspects of the compactified extra dimensions of string theory could, through the Casimir effect observable consequences in the characteristics of nanotechnologic materials, in particular nanotubes. My guess is that there must be some error, or some trick, somewhere. If not this paper would be driving string theory from the realms of cute edge speculative high energy physics to actual applications in one of the most economicaly profitable industries. Too good to be truth probably, but, who knows? Well, I'll read the article carefully sooner and I'll comment more details. But I doubt that I would be the only one to say something about it ;)-

Update: Ok, the article actually doesn't relate string theory extra dimensions and carbone nanotubes. IT only applies the formalism of compactificactions to nanotubes, based on the premise that a nanotube is a cylinder, i.e. a compactified plane. The introductions, and many other parts of the article are somewhat misleading and seem to suggest what I had explained. Also it is misleading the fact that it appears inhep-th. The reason for that possibly is that they make some development of the formalism of compactifications in a general, multidimensional, framework. Possibly that general development could be usefull for people working in string theory, that possibly justifies the inclussion of the paper in hep-th although the primal subjecto of the paper is condensed matter physic.

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