Spectator fields and their imprints on the Cosmic Microwave Background

Abstract

When a subdominant light scalar field ends slow roll during inflation, but well after the Hubble exit of the pivot scales, it may determine the cosmological perturbations. This thesis investigates how such a scalar field, the spectator, may leave its impact on the Cosmic Microwave Background (CMB) radiation and be consequently constrained. We first introduce the observables of the CMB, namely the power spectrum $P_{\zeta }$, spectral index $n_s$ and its running $d{n}_s/d\ln k$, the non-Gaussianities $f_{NL}$, $g_{NL}$ and ${\tau }_{NL}$, and the lack of isocurvature and polarization modes. Based on these studies, we derive the cosmological predictions for the spectator scenario, revealing its consistency with the CMB for inflection point potentials, hyperbolic tangent potentials, and those with a sudden phase transition. In the end, we utilize the spectator scenario to explain the CMB power asymmetry, with a brief tachyonic fast-roll phase.

A thesis submitted to Lancaster University for the degree of Doctor of Philosophy in the Faculty of Science and Technology. 182 pages, 22 figures, 2 tables

References in corpus (27)

• Three Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Polarization Analysis
• Primordial Non-Gaussianities from Inflation Models
• Hemispherical power asymmetry in the three-year Wilkinson Microwave Anisotropy Probe sky maps
• A Hemispherical Power Asymmetry from Inflation
• Multi-brid inflation and non-Gaussianity
• Constraints on cosmic hemispherical power anomalies from quasars
• Primordial Non-Gaussianity in Multi-Scalar Slow-Roll Inflation
• Unifying inflation and dark matter with neutrino masses
• Curvaton Dynamics and the Non-Linearity Parameters in Curvaton Model
• Large Non-Gaussianity Implication for Curvaton Scenario
• Primordial non-Gaussianity from two curvaton decays
• Non-minimally coupled vector curvaton
• Warm hilltop inflation
• DBI-Curvaton
• Supergravity inspired Vector Curvaton
• N-vaton
• Primordial Non-Gaussianity in Models with Dark Matter Isocurvature Fluctuations
• Large Nonlocal Non-Gaussianity from a Curvaton Brane
• Separable and non-separable multi-field inflation and large non-Gaussianity
• Expected dipole asymmetry in CMB polarization
• Spectral Index in Curvaton Scenario
• CMB hemispherical asymmetry from non-linear isocurvature perturbations
• Non-Gaussianity and constraints for the variance of perturbations in the curvaton model
• New features in curvaton model
• Non-Gaussianity and gravitational wave background in curvaton with a double well potential
• Creating perturbations from a decaying field during inflation
• Primordial non-gaussianity from multiple curvaton decay