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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.

 

Mardi sep 18, 2012
Speaker(s): 

The idea that the graviton may be massive has seen a
resurgence of interest due to recent progress which has overcome its

traditional problems.  
I will review this recent progress, which has

led to a consistent ghost-free effective field theory of
a massive graviton, with a stable hierarchy between the graviton mass and the
cutoff, and how this theory has the potential to resolve the naturalness
problem of the cosmological constant.

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Mardi sep 11, 2012
Speaker(s): 

The spectrum of the cosmic microwave background (CMB) is known to be extremely close to a perfect blackbody. However, even within standard cosmology several processes occurring in the early Universe lead to distortions of the CMB at a level that might become observable in the future. This could open an exciting new window to early Universe physics.

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Mardi sep 04, 2012
Speaker(s): 

I will describe a new, generic mechanism for realizing a
period of slowly-rolling inflation through the use of an analog of 'magnetic
drift.' I will demonstrate how the mechanism works through two particular
worked examples: Chromo-Natural Inflation, which exists as a purely 4D
effective theory, and a version that can appear naturally in string theory.

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Mardi aoû 14, 2012
Speaker(s): 

I will introduce the theory and experimental technique of extra-solar planet observation by the gravitational microlensing and give a report on recent results. Then I will discuss the wave optics features in the gravitational microlensing, the analogy of this effect in the astronomical scales to the Young's double slit experiment. Finally I will discuss about the possibility of observation of diffraction patterns in the microlensing experiment.

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Mardi aoû 07, 2012
Speaker(s): 

Tidal stripping of dark matter from subhalos falling into the Milky Way produces narrow, cold tidal streams as well as more spatially extended ``debris flows'' in the form of shells, sheets, and plumes.Here we focus on the debris flow in the Via Lactea II simulation, and show that this incompletely phase-mixed material exhibits distinctive high velocity behavior. Unlike tidal streams, which may not necessarily intersect the Earth's location, debris flow is spatially uniform at 8 kpc and thus guaranteed to be present in the dark matter flux incident on direct detection experiments.

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Jeudi juil 26, 2012

We discuss the shortcomings of Einstein gravity at both the classical and quantum levels. We discuss the motivation for replacing Einstein gravity by conformal gravity. We show how the conformal gravity theory is able to naturally solve the quantum gravity problem, the vacuum zero-point energy problem, the vacuum zero-point pressure problem, the cosmological constant problem, and the dark matter problem.

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Mardi juil 24, 2012
Speaker(s): 

We will discuss the estimated densities of dark matter in the
central regions of galaxies and discuss their inconsistency with
the predictions of cold dark matter only simulations. We will focus on
the satellites of the Milky Way to highlight this issue and then
explore dark matter with significant self-interactions as a
viable alternative. Milky Way satellites also place stringent
constraints on WIMP dark matter models in a completely different way
through Fermi-LAT observations and we will summarize those results.

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Mardi mai 29, 2012
Speaker(s): 

TBA

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Mardi mai 22, 2012
Speaker(s): 

How did inflation actually happen? Precision measurements of statistical properties of primordial fluctuations generated during inflation offer a direct probe of the physics of inflation. When we calculate statistical properties of primordial fluctuations generated during inflation, we usually assume that the initial state of quantum fluctuations is in a preferred vacuum state called Bunch-Davies vacuum. While there is some motivation for choosing such a state, this is an assumption, and thus needs to be tested by observations.

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Mardi mai 15, 2012
Speaker(s): 

In this talk I provide a model where the late time acceleration of the universe emerges from a BCS-like condensation of sterile neutrinos. This scenario can be naturally accommodated by general relativity covariantly coupled to sterile neutrinos, where the neutrinos act like an "aether" field.  We show that when active neutrinos couple to the neutrino condensate, they oscillate at a rate proportional to the dark energy density.  As a result, the oscillation of neutrinos and dark energy are tied in with the same mechanism.

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