The grand challenge of High Energy Theory is to develop a self-consistent description of all the microscopic laws of nature. Along the way, we need answers to questions such as: Is the fundamental structure of space and time continuous or discrete? Is there a symmetry that allows us to generalize Einstein's "equivalence principle" to quantum mechanics? Can our current models of High Energy Physics explain the origin of the Big Bang? Can the fundamental constants of physics be predicted? Or are they thrown down by chance?

Research in High Energy Physics at Brown covers a range of topics from String Theory and M-theory to Black Hole physics, Gravitation and Cosmology, as well gauge theories, QCD and other topics. Faculty in particle theory are Stephon Alexander, Jiji Fan, Antal Jevicki, David Lowe, Marcus Spradlin, Chung-I Tan, and Anastasia Volovich. In addition, the group includes postdoctoral research associates. The group has an active visitor program and runs a weekly seminar series where speakers from around the country come to discuss the latest in research.

**Stephon Alexander**'s research explores the interconnection between the smallest and largest entities in the cosmos by using experimental data in cosmology and particle physics to test, constrain and improve on theories of quantum gravity and beyond the standard model of cosmology and particle physics.

**JiJi Fan** works on particle theories, in particular, beyond Standard Model theories such as Higgs phenomenology, supersymmetry, dark matter models, and signatures. Her recent research is at the interface between elementary particle physics, astrophysics, and cosmology. It combines both theoretical model building and numerical data analyses.

**Antal Jevicki**'s research interests include Quantum Field Theory, String Theory, Quantum Gravity, Black Holes, Nonperturbative and Collective Phenomena. Recently he has been studying the symmetry principles that underlie space-time geometry, and has been developing a new non-commutative formulation of geometry.

**David Lowe** works on a broad range of topics ranging from "nonperturbative" formulations of string theory, to applications of powerful string theory techniques to problems in black hole physics and cosmology. This work is leading to a consistent quantum description of black holes via string theory that matches well with Hawking's early work. As string theory develops it is becoming possible to address cosmological questions from a top down approach. With the wealth of new data on cosmological parameters coming in from experiments, this interface between string theory and cosmology will likely be entering an inflationary phase.

**Marcus Spradlin** is interested in string theory and its applications to particle and gravitational physics. In particular he studies dualities equating quantum gravity to ordinary quantum field theories similar to QCD, which describes the strong nuclear force binding quarks together inside of protons and neutrons. Professor Spradlin explores the implications of dualities and exploits these insights to develop novel calculational tools, aiming towards a mathematical solution of QCD.

**Chung-I Tan**'s research interests include Dynamics of Hadrons, Quantum Chromodynamics, Lattice Gauge Theories, Matrix Models and String Theories, High-Energy Multiparticle Phenomena and Statistical Mechanics of Strings at High-Energy Densities. Using the duality between quantum chromodynamics at large N (the number of gluons is N2) and supergravity, he is understanding many detailed properties of QCD. The brane-world scenario is another topic of investigation, which yields predictions that can be tested at the next round of collider experiments.

**Anastasia Volovich**'s research interests are in formal areas of high energy theory including quantum field theory, general relativity, string theory and related areas in mathematics. Current research interests include scattering amplitudes in quantum field theory and gravity. The goal of this research program is to deepen our understanding of the fundamental properties of gauge and gravity theories by discovering and exploring the hidden mathematical structures of scattering amplitudes and to use these novel structures as much as possible to aid practical calculations for experimentally relevant processes.