The Origin of Matter in the Universe

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The brief period in the early universe from the end of inflation until the development of a thermalized plasma is one of the least understood eras in cosmology. During that era, which is known as "reheating," the particles, fields, and effective low-energy interactions we see today all developed, but the high-energy physics required to describe that time is not known and modeling reheating requires large-scale numerical computations. The PI has coauthored LATTICEEASY, the most widely used program for simulating the reheating era. Most simulations to date, however, have been limited to unrealistically simple models of interacting scalar fields. The PI intends to extend the capabilities of his code to run on clusters of parallel processors and to include gauge fields in its calculations. Using those extended capabilities he will simulate reheating in complex models of high-energy physics and extract testable predictions. An understanding of preheating is important because it introduces extra "handles" (gravitational waves, topological defects) that one might use to constrain the physics involved in inflation. Other observables related to inflationary physics such as the CMB provide constraints on inflation models, but by their nature don't tell us anything about how the inflaton couples to other fields. Information about the couplings will be crucial if we are to move beyond phenomenological models of inflation and really start talking about embedding the inflaton in a model capable of making contact with other areas of particle physics. The PI intends to develop a program for training undergraduate students in numerical computation. This will include involving undergraduate research assistants in writing and running numerical simulations, creating computational units for two of the required courses in the Smith physics major and developing a course on computation built around examples drawn from the PI's cosmological research.