Skip to main content

Understanding the Origin of Cosmic Structure

Final Report Summary - COSMICDAWN (Understanding the Origin of Cosmic Structure)

The early universe is a “laboratory” for testing physics at very high energies, up to a trillion times greater than the energies reached by the Large Hadron Collider. The origin of structure in the universe is deeply tied to this extreme physics, which is imprinted in the primordial ripples seen in the cosmic microwave background (CMB). CMB data have thus far led the way in constraining early universe physics, exemplified by the data from ESA’s Planck satellite. Meanwhile, we are acquiring enormous volumes of data on the large scale structure (LSS) of the universe, the “scaffolding” of dark matter traced by galaxies. These next generation galaxy surveys – such as the Dark Energy Survey (DES) – will rival the CMB in their ability to unlock the secrets of the primordial universe.

The CosmicDawn team used the Planck and DES data to rigorously test the theory of inflation, the dominant paradigm for the origin of cosmic structure, and to seek signatures of new physics that are likely to exist at these unexplored energies. Our aim was to go beyond simply testing generic predictions of the inflationary paradigm, to gain a fundamental understanding of the physics responsible for the origin of cosmic structure. In working towards this goal, the team focused on: (1) theoretical modelling at the cutting edge of fundamental physics (describing not just the inflationary period but also pre- and post-inflationary physics); (2) development of powerful wavelet and filtering techniques to extract these physical signatures; (3) introduction of CMB techniques new to LSS analyses to facilitate major sensitivity gains; (4) use of advanced Bayesian statistical methods to extract reliable information from the data; and (5) a deep understanding of data limitations and control of systematics. Over the reporting period, our research led to 125 publications, including interdisciplinary papers with high energy theorists, numerical relativists, and condensed matter physicists, and cross-disciplinary papers in information engineering and high performance computing. The team made critical contributions to obtaining the best available measurements from the cutting edge Planck and DES datasets, and explored the implications of these measurements for fundamental theory using theoretical modelling in research that significantly extended the state of the art in all five Themes of the project.