Joshua Erlich Assistant Professor of Physics Contact Information: Department of Physics College of William & Mary P.O. Box 8795 Williamsburg, VA 23187-8795 Small Hall, Room 220 Phone: (757)221-3763 erlich@physics.wm.edu

Research:

I am a member of the High Energy Theory Group at the College of William & Mary. My research is focused on particle physics and cosmology beyond the Standard Model.

Some uses of string theory

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, a.k.a. 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, certain kinds of quantum field theories are now known to make the same predictions as other theories that a priori seem completely different. So which one is right? String theory says that it doesn't matter. There may be different ways to describe the interactions of particles, and we are free to use whichever description we like. 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 thanks to some 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, to make more accurate predictions will probably require those computations being done on big supercomputers, by people like Kostas Orginos here at William & Mary.

We've also constructed simple models of hypothetical new partcicles 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.

Related references:

J. Erlich, E. Katz, D. Son, M. Stephanov, QCD and a holographic model of hadrons, Phys.Rev.Lett. 95:261602, 2005.
J. Erlich, G. Kribs, I. Low, Emerging holography, Phys. Rev. D73:096001, 2006.
C. Carone, J. Erlich, J.A. Tan, Holographic bosonic technicolor, Phys. Rev. D75:075005, 2007.
C. Carone, J. Erlich, M. Sher, Holographic electroweak symmetry breaking from D-branes, Phys. Rev. D76:015015, 2007.

Complete list of my publications

Teaching:

• Physics 722, Spring 2008: Quantum Field Theory
• Physics 201, Fall 2007: Modern Physics
• Physics 722, Spring 2007: Quantum Field Theory
• Physics 721, Fall 2006: Advanced Quantum Mechanics
• Physics 722, Spring 2006: Quantum Field Theory
• Physics 721, Fall 2005: Advanced Quantum Mechanics
• Physics 690, Spring 2005: Particle Physics and Gravity in Extra Dimensions

Graduate Students:

Brian Glover
Jong Anly Tan

Undergraduate Students:

Keith Bechtol (graduated May, 2007. Grad school, Stanford U.)
Andrew McGowan
Lukas Osborn