Cosmology & Gravitation

This series consists of talks in the areas of Cosmology, Gravitation and Particle Physics.

Seminar Series Events/Videos

Currently there are no upcoming talks in this series.

 

Tuesday May 24, 2011
Speaker(s): 

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.

Collection/Series: 
Scientific Areas: 

 

Tuesday May 17, 2011
Speaker(s): 

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.

Collection/Series: 
Scientific Areas: 

 

Tuesday May 10, 2011
Speaker(s): 

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

Collection/Series: 
Scientific Areas: 

 

Wednesday Apr 20, 2011
Speaker(s): 

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. Single particle excitations also decay into two particle states, leading to particle production that hastens the exiting of modes from the de Sitter horizon resulting in the production of \emph{entangled superhorizon pairs} with a population consistent with unitary evolution.

Collection/Series: 
Scientific Areas: 

 

Tuesday Apr 19, 2011
Speaker(s): 

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].

Collection/Series: 
Scientific Areas: 

 

Tuesday Apr 05, 2011
Speaker(s): 

One of the great promises of the Advanced LIGO era is the prospect of
integrating gravitational wave astronomy into the greater astronomical
community. This will allow for measurements that cross spectral bands
and provide new paths for insight into some of the most violent
processes in the universe. In this talk I'll discuss past and present
efforts with Initial and Enhanced LIGO to search for transients with
both electromagnetic and gravitational wave signatures, with special
focus on electromagnetic followups of inspiral events and an eye

Collection/Series: 
Scientific Areas: 

 

Tuesday Mar 29, 2011
Speaker(s): 

 

Tuesday Mar 15, 2011
Speaker(s): 

I propose late-time moduli decay as the common origin of baryons and dark matter. The baryon asymmetry is produced from the decay of new TeV scale particles, while dark matter is created from the chain decay of R-parity odd particles. The baryon and dark matter abundances are mainly controlled by the dilution factor from moduli decay, which is typically in the range 10^{-9}-10^{-7}. The exact number densities are determined by simple branching fractions from modulus decay, which are expected to be of similar order in the absence of symmetries.

Collection/Series: 
Scientific Areas: 

 

Tuesday Mar 08, 2011
Speaker(s): 

If the universe is a quantum mechanical system it has a quantum state. This state supplies a probabilistic measure for alternative histories of the universe. During eternal inflation these histories typically develop large inhomogeneities that lead to a mosaic structure on superhorizon scales consisting of homogeneous patches separated by inflating regions. As observers we do not see this structure directly. Rather our observations are confined to a small, nearly homogeneous region within our past light cone.

Collection/Series: 
Scientific Areas: 

 

Thursday Mar 03, 2011
Speaker(s): 

In this talk I will discuss a new class of cosmological scalar fields. Similarly to gravity, these theories are described by actions linearly depending on second derivatives. The latter can not be excluded without breaking the generally covariant formulation of the action principle. Despite the presence of these second derivatives the equations of motion are of the second order. Hence there are no new pathological degrees of freedom.

Collection/Series: 
Scientific Areas: 

Pages