Talks

At the beginning of the 20th century Einstein published three revolutionary ideas that changed forever how we view Nature. At the beginning of the 21st century Einstein\'s thinking is shaping one of the key scientific and technological wonders of contemporary life: atomic clocks, the best timekeepers ever made. Such super-accurate clocks are essential to industry, commerce, and science; they are the heart of the Global Positioning System (GPS), which guides cars, airplanes, and hikers to their destinations. Today, atomic clocks are still being improved, using Einstein\'s ideas to cool the atoms to incredibly low temperatures. Atomic gases reach temperatures less than a billionth of a degree above Absolute Zero, without solidifying. Such atoms enable clocks accurate to better than a second in 60 million years as well as both using and testing some of Einstein\'s strangest predictions. This will be a lively, multimedia presentation, including experimental demonstrations and down-to-earth explanations about some of today\'s most exciting science. Low temperature physics, atomic clock, global positioning system, laser cooling, Bose Einstein condensate, photoelectric effect, Brownian motion, special relativity

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. We show that the idea to use additional non-gauge, high-scale mirror-sector dynamics to decouple the mirror fermions without breaking the gauge symmetry might lead to a practically manageable solution. We demonstrate, using the exact lattice chirality, that partition functions of lattice gauge theories with vector like fermion representations can be split into \'light\' and \'mirror\' parts, and each contains a chiral representation. Such a splitting is only well defined when both sectors are separately anomaly free. We also prove that, the generating function and therefore the spectrum of an arbitrary chiral gauge theory is a smooth function of the background gauge field, if and only if the anomaly free condition is satisfied. We reached this conclusion by proving some very general properties of an arbitrary chiral gauge theory on lattice, and the results should be of importance for further studies in this field.

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 also point out several shortcomings of other, recent investigations into the decay mechanisms of the KK relics.

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.

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.