Search Talks

Inflation is generically a never ending process, with new \'pocket universes\' constantly being formed. All possible events will happen an infinite number of times in such an eternally inflating universe. Unless we learn how to compare these infinities, we will not be able to make any predictions at all. I will discuss some proposed approaches to this \'measure problem\'.

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.

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.