String theory is the quantum theory of vibrating strings. Although string theory has not yet proven itself as a theory of everything, it has the remarkable feature that Einstein's theory of gravity, general relativity, comes out of the theory automatically. This, and the fact that string theory might also describe all of the elementary particles that compose everything in the universe, makes it a subject worthy of the effort being poured into it.
String theory has already been useful in teaching us new things about quantum field theories, the kinds of theories that describe the interactions of all the known particles except gravity. For example, string theory has taught us that there may be very different descriptions of the same physical system, and the various descriptions may even have different numbers of spatial dimensions! Some theories, like the theory of the strong interactions that hold protons and neutrons together, are quite complicated. If we're lucky, there may be a much simpler description which we can try to construct using hints from recent developments in string theory, and that's just what we've been doing.
So far we've been able to construct simple models that do a good job reproducing experimental results like the masses, decay rates, and interactions of some particles like rho mesons and pions. Using the usual description of the strong interactions it takes huge supercomputers months to calculate these things, but it only takes us a few minutes on a laptop. On the other hand, although we think we've captured the most important aspects of the strong interactions in our model, we are extending a string theory-based analysis outside its expected range of validity. To make more accurate predictions will require those computations being done on big computer clusters by people like Kostas Orginos and Will Detmold here at William & Mary.
We've also constructed simple models of hypothetical new particles and interactions that would explain how the elementary particles get their mass. We've used these models to make predictions for certain processes that may be discovered at the Large Hadron Collider in the next few years.
D. Albrecht, J. Erlich, Pion
condensation in holographic QCD, accepted for publication, Phys. Rev. D, 2010.
J. Erlich, C. Westenberger, Tests
of Universality in AdS/QCD, Phys. Rev. D79:066014, 2009.
C. Carone, J. Erlich, M. Sher,
Holographic electroweak symmetry breaking from D-branes,
Phys. Rev. D76:015015, 2007.
C. Carone, J. Erlich, J.A. Tan,
Holographic bosonic technicolor,
Phys. Rev. D75:075005, 2007.
J. Erlich, G. Kribs, I. Low,
Emerging holography, Phys. Rev. D73:096001, 2006.
J. Erlich, E. Katz, D. Son, M. Stephanov,
QCD and a
holographic model of hadrons,
Phys.Rev.Lett. 95:261602, 2005.
Article by
Nick Evans in Physics World