Examining the Origin of Structure

Syracuse University, Syracuse NY

Investigators

Abstract

The early universe must have contained tiny initial fluctuations, which later grew by the attractive force of gravity as the universe expanded, to become the structures we observe in the universe today. This proposal aims to empirically examine the properties of these primordial fluctuations, and to refine theoretical predictions about their properties. On the phenomenological side, and building on previous work by the PI, the proposal discusses tests of statistical homogeneity and isotropy. If averages of cosmic density fields are invariant under translations, we speak of statistical homogeneity; if they are additionally invariant under rotations we speak of statistical isotropy. Both are two of the key assumptions that underlie most of our analyses of the origin and growth of structure, so it is crucial to test both empirically. On the theoretical side, the PI proposes to further study the predictions of inflation, the leading explanation for the origin of the primordial perturbations. At the end of inflation, the inflaton field must decay into the hot radiation of the Big Bang, in a process known as reheating. The PI plans to study the survival of non-adiabatic perturbations after inflation, and several aspects related to the quantum nature of the inflaton decay. These studies are important to unveil the details of a process that remains hidden by the resulting thermal equilibrium. Reheating may also have indirect implications on the Gaussianity of the primordial perturbations. Calculations of the degree of primordial non-Gaussianity produced during inflation have neglected the couplings needed for the universe to reheat. The PI intends to include the effects of such couplings, in order to verify whether they can be neglected, and thus confirm one of the key predictions of single-field inflationary models. The broader impacts of this proposal are as follows: As a major component of his efforts in public education, the PI plans to draw from his Hispanic background to promote the diffusion of cosmology among Hispanic minorities in the Syracuse area. In collaboration with the Spanish Action League of Onondaga County he proposes to extend the multi-disciplinary educational program in astronomy and cosmology addressed to Hispanic children that he started in 2007. The program is structured in a series of weekly ninety minute sessions in which children aged six to ten are exposed to basic concepts in astronomy and cosmology. In the coming years, the PI intends to build on the successes of the first year of life of the program, and to correct and address the challenges that have emerged so far.