This series consists of talks in the areas of Cosmology, Gravitation and Particle Physics.
There are many situations in cosmology that
motivate the study of scalar fields with higher-derivative actions. The best-known
such situations are probably k-inflation (with DBI-inflation being a special
case) and models based on galileon theories, but even eternal inflation and
cyclic universes provide good reasons to study such theories. After an extended
discussion of the motivations, I will show how scalar field theories with
higher derivatives can be constructed in (minimal, 4-dimensional) supergravity,
The question of finite range gravity, or equivalently,
whether graviton can have a non-zero mass, has been one of the major challenges
in classical field theory for the last 70 years.
We consider the stellar-dynamical processes which lead to
the capture or tidal disruption of stars by a supermassive black hole, review
the standard theory of two-body relaxation and loss-cone repopulation in
spherical galactic nuclei, and extend it to the axisymmetric and triaxial
nuclear star clusters.
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.
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.
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.
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.
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.
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.
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.