Theoretical Particle Physics

Members of our group work in particle physics, cosmology, and string theory, often with overlap between the subjects.

Particle Physics

While the Standard Model of particle physics is an unreasonably effective description of our universe, it cannot be the complete story. The prospect of beyond the standard model (BSM) physics is one of the most exciting theoretical and experimental challenges of our time. Our group is interested in both model building and phenomenology of BSM physics, including understanding the role supersymmetry might play in our universe. Both bottom up and top down approaches are of interest. In the bottom up approach physics at the sensitivity frontier is of interest, which may allow exploration of PeV scale phenomena. Of specific interest in the top down approach is model building using supergravity and grand unification and the exploration of new physics at the Large Hadron Collider within this framework. Implications of unified models for proton stability as well as areas on the interface of particle physics and cosmology such as dark matter and baryon asymmetry are of interest. In addition, constraints from UV physics, especially string theory, may place bounds on what we expect to see at the LHC. Such stringy models are therefore of great interest.

Cosmology

Cosmology is the study of the early universe. It includes the physics directly following the initial singularity, know as inflation, and numerous aspects of post-inflationary physics. It is a very exciting direction that could connect high energy experiment and theory in the coming years, and our group is particularly interested in certain aspects of cosmology.

First, the matter in our universe is mainly comprised of what is known as dark matter, which does not interact electromagnetically. It is of great interest to identify this dark matter, and understand its interactions and the role it plays in structure formation and other aspects of post-inflationary cosmology. In addition, our group is interested in inflation, which is a rapid expansion of space that is believed to have occurred in the very early universe. Inflation is an especially exciting theoretical laboratory, as it is often sensitive to physics near or at the Planck scale. In particular, large field inflation is sensitive to Planck suppressed operators that become important as the inflaton traverses a (super) Planckian field range. This puts inflation in the unique situation of possibly probing quantum gravity directly in a measurable way, if primordial B-modes are detectable. Such a measurement would may allow us to learn something about quantum gravity.

String Theory

String theory is the leading candidate for a UV complete theory of quantum gravity. Our group is interested in understanding the possible effective field theories that string theory, and its various generalizations, can realize in four dimensions. In particular, the string landscape is a vast set of string vacua whose vast size poses a challenge for the predicitivity of string theory. We are interested in understanding the landscape as a whole. This is a daunting task, but we are taking several new approaches, including machine learning and data science, as well as setting out to understand the basic building blocks from which all the vacua are generated, which may allow us to gain a handle on the landscape. Of course, a necessary step to understanding the landscape is to understand the underlying string theory and the geometry of string compactifications, both of which are very active research areas in our group. In particular, F-theory provides a strong coupling generalization of string theory, and accounts for the largest set of vacua known so far. Understanding F-theory as a fundamental theory requires heavy geometric machinery, which is another main interest of our group.