Dissertation

Field Theory for Cosmology: An Effective Approach

Perko, Ashley Nicole

2017

Overview

Effective field theory (EFT) is our most successful tool to date for exploring the fundamental processes of particle physics: it has been able to describe all know particle interactions in the lab to astonishing accuracy. We are now entering an era of precision cosmology, where we can use the power of EFT, a tool that has only recently been applied to the field of cosmology, to fully make use of cosmological observations. This thesis comprises recent work applying effective field theory in the context of early-universe cosmology and large-scale structure (LSS).Observations of the cosmic microwave background (CMB) have not yet found evidence of primordial non-gaussianity, a key signature of the interactions during inflation. However, surveys of the distribution of the large-scale structure of matter in the universe have the potential to produce limits competitive with CMB surveys because they map the universe in three dimensions, while the CMB is a two-dimensional snapshot of an instant in time. Compared to the CMB, however, this field possesses considerable hurdles in matching primordial signals to observations. While the CMB was produced at an early enough time that its structures were formed by linear evolution of the primordial signal, large-scale structure (LSS) is observed at late times, when the primordial signal has been obscured due to the non-linear clustering of gravity. The nonlinear clustering of matter is a problem well suited for EFT, because in the bottom-up approach, we can “integrate out” the small-scale dynamics of the matter, parameterizing its effect on large scales in a spatial-derivative expansion suppressed by the scale at which the density perturbation becomes nonlinear.The work of the first half of this thesis uses EFT to extends our understanding of inflation in the quasi-nonlinear regime, by extending the inflationary consistency conditions to second order, and including slow-roll corrections to the phase transition to eternal inflation. The latter part explores the use of EFT in LSS, including introducing the effects of normal (baryonic) matter to the theory, which previously described only dark matter, and making the first step from theory to observations by computing the statistics of different populations of halos and galaxies measured in redshift space.

• Publisher: ProQuest Dissertations & Theses
• Subject: Astronomy / Astrophysics / Particle physics
• ISBN: 9798698508489