This award funds the research activities of Professor Sarah Shandera at Pennsylvania State University. There is excellent, if indirect, evidence that our universe underwent an early period of very rapid expansion (inflation) which set the stage for the evolution to the cosmology we currently observe. Although we expect that inflation can be explained in terms of particle physics, we do not yet have a precise understanding of the nature of the particles responsible. Particle interactions can be constrained by the way they induce couplings in observable properties of the cosmic density field on different scales. This research project examines the implications of coupling between scales that are observable to scales that are outside of our current cosmological window. In particular, the PI will study how observations made in a finite volume of the universe constrain particle physics models of inflation which make predictions about statistics in a much larger, unobservable, volume. The PI will also develop workshop modules for elementary and high school students based on the theme of understanding the size and dynamical evolution of the universe.
The PI has already shown that when the curvature inhomogeneities on very different scales are coupled, our observed universe is likely to have biased statistics compared to the mean predicted for a larger post-inflationary volume. In other words, there is a new source of cosmic variance in comparing observations in our Hubble volume to theory. Through this grant, the PI proposes to further develop the framework for constraining interacting inflation theories, compatible with observations in a finite universe. She will map out the extent to which the cosmic variance from coupling to superhorizon modes can add new uncertainties in comparing measurements of the primordial scalar curvature inhomogeneities to predictions from theory. She will work out which qualitative aspects of particle physics scenarios for inflation can be mimicked or obscured by cosmic variance.
