### Probing Early and Late Inflations Beyond Tilted ΛCDM

### Zhiqi Huang

Doctor of Philosophy 2010

Graduate Department of Astronomy and Astrophysics, University of Toronto
The topic of this thesis is about cosmic inflations, including the early-universe inflation
that seeds the initial inhomogeneities of our universe, and the late-time cosmic acceleration
triggered by dark energy. The two inflationary epochs have now become part of
the standard ΛCDM cosmological model. In the standard paradigm, dark energy is a
cosmological constant or vacuum energy, while the early-universe inflation is driven by
a slowly rolling scalar field. Currently the minimal ΛCDM model with six parameters
agrees well with cosmological observations.

If the greatest achievement of the last twenty golden years of cosmology is the ΛCDM
model, the theme of future precision cosmology will be to search for deviations from
the minimal ΛCDM paradigm. It is in fact expected that the upcoming breakthroughs
of cosmology will be achieved by observing the subdominant anomalies, such as non-
Gaussianities in the Cosmic Microwave Background map. The aim of this thesis is then
to make theoretical predictions from models beyond ΛCDM, and confront them with
cosmological observations. These models include: 1) a new dark energy parametrization
based on quintessence models; 2) reconstructing early-universe inflationary trajectories,
going beyond the slow-roll assumption; 3) non-Gaussian curvature fluctuations from preheating
after the early-universe inflation; 4) infra-red cascading produced by particle
production during inflation; 5) preheating after Modular inflation; 6) decaying cold dark
matter. We update the cosmological data sets – Cosmic Microwave Background, Type
Ia supernova, weak gravitational lensing, galaxy power spectra, and Lyman-$alpha; forest – to
the most current catalog, and run Monte Carlo Markov Chain calculations to obtain the
likelihood of parameters. We also simulate mock data to forecast future observational
constraints.