### Non-technical research description

I aim to make this discussion of my research broadly accessible. I have been publicly funded for most of my career, so I should explain to taxpayers the work they have made possible. I also hope to contribute to public understanding of science, an important issue in its own right. If you have any questions about my research, you are welcome to contact me.

My research focuses on theories of particle physics that involve strong interactions. The most familiar strongly interacting theory is quantum chromodynamics (QCD), the "color" theory of the strong nuclear force that binds quarks and gluons into composite particles such as protons. To understand why we say this interaction is "strong", imagine pulling apart two quarks: separating them by a femtometer (10^{-15} m) would require a force of roughly 10 tons to balance the attractive color force pulling the quarks together. That's strong.

Strongly interacting theories are very challenging to study because they cannot be treated by the standard analytical approach known as perturbation theory. This method treats interactions as minor corrections ("perturbations") to simpler systems, and can only be applied when interactions are weak in strength. In order to study strong dynamics from first principles, I perform numerical lattice field theory calculations. In this approach, space and time are replaced by a regular, finite lattice of discrete sites connected by links. The fields involved in the theory are likewise discretized, and defined on the lattice in such a way that we recover the original theory in continuous spacetime when the lattice is taken to be infinitely large, with its sites infinitesimally close together. The discretized theory involves "only" millions of degrees of freedom, which allows us to stochastically calculate observables through long-established numerical techniques known as Monte Carlo importance sampling. These techniques require large-scale supercomputing.

The great benefit of lattice calculations is that they provide non-perturbative means to study strongly interacting systems. Lattice field theory is currently the only method that can provide quantitatively reliable predictions for strongly interacting theories from first principles, and this will remain the case for the foreseeable future. A disadvantage of the approach is that it is extremely computationally intensive, and continues to push the bounds of high-performance computing.

My work in lattice field theory has addressed several different topics over the years, each of which is summarized on a separate page:

- Quantum chromodynamics and the strong nuclear force: The application of lattice techniques to study the strong nuclear force is an active and very successful field, which has provided many important predictions for direct comparison with experiments.
- Dynamical electroweak symmetry breaking and the origin of mass: New strong interactions (that is, strong dynamics distinct from the strong nuclear force) may underlie the existence of masses for elementary particles, related to the Higgs boson recently discovered by Large Hadron Collider experiments at CERN, the European Organization for Nuclear Research. This is a much more speculative line of research: Not only do we not yet have definitive evidence for the existence (or non-existence) of such new strong dynamics, we lack the decades of experimental input that helped develop our understanding of the strong nuclear force and the underlying theory of quantum chromodynamics.
- High-performance computing: To make our research possible and practical, we must develop novel computational algorithms, and exploit advances in computing hardware. It can be most efficient to explore these questions in the context of simpler test systems, which may provide more accessible projects for beginners to enter the field while still contributing significantly to its advance.

Last modified 6 September 2015