Probing Fundamental Theories with Early Universe Observations

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I work on theoretical cosmology and theories of gravity, using models of the early Universe and black holes to test for potential new physics. My proposed research focuses on how inflation ended and reheating of the universe happened, and how to detect observable traces of this process in the cosmic microwave background radiation and the large scale structure of the universe. The idea of inflation neatly solves several long-standing issues in cosmology, and has been spectacularly confirmed by observations of the Cosmic Microwave Background (CMB) anisotropies. While the Universe is inflating, its contents are cold. But eventually, inflation has to end and the field driving the inflation must decay, depositing energy into high-energy particles. This reheating "boils" the vacuum and starts the hot big bang history as we know it. While inflation creates all the energy in the universe, reheating likely creates all the entropy. Very little is known about the fundamental physics at these energy scales, and cosmological observations could be our only source of information for the foreseeable future. While no photons reach us directly from this epoch as the universe is filled with hot plasma and is opaque until recombination, the expansion history of the early universe is imprinted on the sky in the form of primordial curvature fluctuations, and CMB observations just reached precision required to disentangle other effects from Gaussian fluctuations due to simple inflation. The accuracy of my methods enabled us to show that preheating generically creates primordial non-Gaussian curvature fluctuations on top of the ones produced by inflation, manifested in large cosmic structures and as polarization and temperature CMB anisotropies. The non-Gaussianity is often intermittent, and is driven by caustics forming in the nonlinear evolution in the field phase space. In the simplest quartic model of preheating, it is manifested as intermittent cold spots, similar to the one observed on the CMB sky. My immediate goal is to develop analysis tools that search for this type of non-Gaussianity in the CMB maps, and explore constraints Planck data can place on preheating, as well as other generic deviations from the statistical isotropy and Gaussianity of primordial fluctuations one expects from inflation. I joined Planck collaboration to achieve these goals, and I am currently working on isotropy and statistics analysis and inflation for the collaboration. In the long-term, I plan to study how thermalization proceeds after reheating, and investigate how large scale structure formation traces primordial fluctuations from reheating. My research program provides numerous opportunities for HQP training, including highly desirable skills in computational methods and parallel computing in demand by industry, and access to the skills needed to work with the most recent temperature and polarization CMB data from Planck.