14th International Symposium on Particles, Strings and Cosmology (PASCOS '08)
With LHC commissioned in just a few month ahead, all sorts of ideas about physics beyond the standard model are being explored intensively. A strong-coupling chiral theory appearing at TeV scale remains a possibility but also a very hard scenario to study. When it comes to strongly coupled theories, lattice regularization is by far the most reliable method. But defining exact chiral gauge theory on the lattice remains a difficult problem on its own.
Within the context of F-theory compactified on Calabi-Yau fourfolds, we describe a class of string theory vacua which contain several features necessary in supersymmetric grand unified models of particle physics. Focussing on a simple class of local Calabi-Yau fourfolds, we explain how the matter content and superpotential in four dimensions are determined by a topological gauge theory. Along these lines, we present some minimal examples of GUT models.
If light scalar fields are present at the end of inflation, their nonequilibrium dynamics can produce non-Gaussian density perturbations. Lattice field theory simulations show that this effect can be very strong in the massless preheating model. It is therefore an important factor in assessing the viability of inflationary models. I present a phenomenological model that can be used to calculate the perturbations analytically.
The process of reheating in warped brane world models was initially thought to be quite efficient. However, the identification of long-lived Kaluza-Klein (KK) relics associated with isometries along the internal directions suggests that reheating may not be efficient, and may conflict with BBN and baryogenesis constraints. This talk discusses processes which may accommodate their decay and quantifies their expectant lifetimes, resulting in strong constraints on the parameters of the underlying theory.
We consider a Born-Infeld like action for gravity coupled to an external connection field. We show that the equation of state of this fluid interpolates between dark matter and dark energy. We also show that on galactic scales this system predicts asymptotically flat rotation curves. This action is motivated by looking at a regime where the metric vanishes, and replacing the big bang by a smooth transition between a topological manifold to a Riemannian manifold.