This series consists of talks in the areas of Cosmology, Gravitation and Particle Physics.
Cosmic strings are predicted to arise in both inflationary
and non-inflationary cosmological models. The signatures of
such strings will stand out particularly well at higher
redshifts. I will discuss how to look for these signatures
in CMB redshift and polarization maps and in 21cm redshift
String theory should give a well-defined answer to the following question: What is the state of matter in the limit of infinite energy density? We use results obtained from the understanding of black hole entropy to conjecture this equation of state, noting that the maximum entropy state in string theory has vastly more entropy than the states used in traditional approaches to early Universe Cosmology. The evolution of the Universe with this equation of state can be obtained in closed form.
It is argued that the correct quantization of a scalar field theory in de Sitter spacetime involves a de Sitter invariant state which is not the Bunch-Davies vacuum. A novel but natural de Sitter invariant alternative exists and it is suggested that this and is the prefered state for scalar field theories. The argument is based on the exact solution of an interacting scalar field theory.
Though the observed CMB is at very low energy, it encodes ultra high-energy physics in spatial variations of the photon temperature and polarization fluctuations. This effect is believed to be dominated by the initial quantum state of the Universe. I will describe the first theoretical tools by which to construct such a state from fundamental physics.
Recently, emergent phenomena have started to attract more attention. Instead of assuming a symmetric world, one begins with a chaotic one. In this talk, I will describe this picture, discuss the main constraints on emergence, and then present a few phenomenological procedures that can be implemented to study the emergent phenomena.
The model of local non-Gaussianity, parameterized by the constant non-linearity parameter fNL, is an extremely popular description of non-Gaussianity. However, a mild scale-dependence of fNL is natural. This scale dependence is a new observable, potentially detectable with the Planck satellite, which helps to further discriminate between models of inflation. It is sensitive to properties of the early universe which are not probed by the standard observables.
In recent years, a number of observations have highlighted anomalies that might be explained by invoking dark matter annihilation. The excess of high energy positrons in cosmic rays reported by the PAMELA experiment is only one of the most prominent examples of such anomalies. Models where dark matter annihilates offer an attractive possibility to explain these
We use a field theoretic generalization of the Wigner-Weisskopf method to study the stability of the Bunch-Davies vacuum state for a massless, conformally coupled interacting test field in de Sitter space. A simple example of the impact of vacuum decay upon a non-gaussian correlation is discussed.
After reviewing the basics of Coleman deLuccia tunneling, especially in the thin-wall limit, I discuss an (almost) exact tunneling solution in a piecewise linear and quadratic potential. A comparison with the exact solution for a piecewise linear potential demonstrates the dependence of the tunneling rate on the exact shape of the potential.
Finally, I will mention applications when determining initial conditions for inflation in the landscape. Based on arXiv:1102.4742 [hep-th].