A New Mechanism for Bubble Nucleation: Classical Transitions (2009)
Easther, Richard, Giblin Jr, John T., Hui, Lam, Lim, Eugene A.
Given a scalar field with metastable minima, bubbles nucleate quantum mechanically. When bubbles collide, energy stored in the bubble walls is converted into kinetic energy of the field. This kinetic...
The "in-in" Formalism and Cosmological Perturbations (2009)
Adshead, Peter, Easther, Richard, Lim, Eugene A.
We describe an efficient scheme for evaluating higher order contributions to primordial cosmological perturbations using the "in-in" formalism, which is the basis of modern calculations of...
Cosmology With Many Light Scalar Fields: Stochastic Inflation and Loop Corrections (2008)
Adshead, Peter, Easther, Richard, Lim, Eugene A.
We explore the consequences of the existence of a very large number of light scalar degrees of freedom in the early universe. We distinguish between participator and spectator fields. The former have...
Thermal Inflation and the Gravitational Wave Background (2008)
Easther, Richard, Giblin Jr, John T., Lim, Eugene A., Park, Wan-Il, Stewart, Ewan D.
We consider the impact of thermal inflation -- a short, secondary period of inflation that can arise in supersymmetric scenarios -- on the stochastic gravitational wave background. We show that while...
Generation and Characterization of Large Non-Gaussianities in Single Field Inflation (2008)
Chen, Xingang, Easther, Richard, Lim, Eugene A.
Inflation driven by a single, minimally coupled, slowly rolling field generically yields a negligible primordial non-Gaussianity. We discuss two distinct mechanisms by which a non-trivial potential...
Gravitational Waves From the End of Inflation: Computational Strategies (2007)
Easther, Richard, Giblin Jr, John T., Lim, Eugene A.
Parametric resonance or preheating is a plausible mechanism for bringing about the transition between the inflationary phase and a hot, radiation dominated universe. This epoch results in the rapid...
The Eternal Sunshine of the Spotless Mind (2007)
Easther, Richard, Lim, Eugene A.
We extend the worldline measure for pocket formation in eternal inflation to allow for time-ordered bubble formation. Such a time-ordering is equivalent to imposing a preferred time-slicing on the...
Gravitational Wave Production At The End Of Inflation (2006)
Easther, Richard, Giblin Jr, John T., Lim, Eugene A.
We consider gravitational wave production due to parametric resonance at the end of inflation, or ``preheating''. This leads to large inhomogeneities which source a stochastic background of...
Large Non-Gaussianities in Single Field Inflation (2006)
Chen, Xingang, Easther, Richard, Lim, Eugene A.
We compute the 3-point correlation function for a general model of inflation driven by a single, minimally coupled scalar field. Our approach is based on the numerical evaluation of both the...
Stochastic Gravitational Wave Production After Inflation (2006)
Easther, Richard, Lim, Eugene A.
In many models of inflation, the period of accelerated expansion ends with preheating, a highly non-thermal phase of evolution during which the inflaton pumps energy into a specific set of momentum...
Counting Pockets with World Lines in Eternal Inflation (2005)
Easther, Richard, Lim, Eugene A., Martin, Matthew R.
We consider the long standing puzzle of how to obtain meaningful probabilities in eternal inflation. We demonstrate a new algorithm to compute the probability distribution of pocket universe types,...
Armendariz-Picon, C., Lim, Eugene A.
We study gravitationally bound static and spherically symmetric configurations of k-essence fields. In particular, we investigate whether these configurations can reproduce the properties of dark...
Can We See Lorentz-Violating Vector Fields in the CMB? (2004)
We investigate the perturbation theory of a fixed-norm, timelike Lorentz-violating vector field. After consistently quantizing the vector field to put constraints on its parameters, we compute the...
Lorentz-Violating Vector Fields Slow the Universe Down (2004)
Carroll, Sean M., Lim, Eugene A.
We consider the gravitational effects of a single, fixed-norm, Lorentz-violating timelike vector field. In a cosmological background, such a vector field acts to rescale the effective value of...
Can we see Lorentz-violating vector fields in the CMB? / (2004)
Thesis (Ph. D.)--University of Chicago, Dept. of Astronomy and Astrophysics, Aug. 2004.
Constraining Cut-off Physics in the Cosmic Microwave Background (2003)
Okamoto, Takemi, Lim, Eugene A.
We investigate the ability to constrain oscillatory features in the primordial power spectrum using current and future cosmic microwave background observations. In particular, we study the...
Scale Invariance without Inflation? (2003)
Armendariz-Picon, C., Lim, Eugene A.
We propose a new alternative mechanism to seed a scale invariant spectrum of primordial density perturbations that does not rely on inflation. In our scenario, a perfect fluid dominates the early...
Vacuum Choices and the Predictions of Inflation (2003)
Armendariz-Picon, C., Lim, Eugene A.
In the presence of a short-distance cutoff, the choice of a vacuum state in an inflating, non-de Sitter universe is unavoidably ambiguous. The ambiguity is related to the time at which initial...