Since 2002 Perimeter Institute has been recording seminars, conference talks, and public outreach events using video cameras installed in our lecture theatres. Perimeter now has 7 formal presentation spaces for its many scientific conferences, seminars, workshops and educational outreach activities, all with advanced audio-visual technical capabilities. Recordings of events in these areas are all available On-Demand from this Video Library and on Perimeter Institute Recorded Seminar Archive (PIRSA). PIRSA is a permanent, free, searchable, and citable archive of recorded seminars from relevant bodies in physics. This resource has been partially modelled after Cornell University's arXiv.org.
I will present a model of inflation in string theory, where the inflaton field corresponds to a Wilson line in the worldvolume of a D-brane, and in the presence of magnetic flux. Inflation ends in a hybrid fashion, when the Wilson line achieves a critical value and an open string mode becomes tachyonic. This scenario predicts a nearly flat, or red tilted, spectrum of scalar perturbations, with negligible primordial gravitational waves. Interestingly, there is a simple compactification in which the eta-problem, appearing in models of brane inflation, is absent.
About 20-30 years ago, scientific community was interested in knowing whether dark matter can carry gauge charges. The answer was found to be no. Today, we can ask a similar question: Can dark energy carry gauge charges? The answer this time seems to be yes. We study the possibility that the current accelerated expansion of the universe is driven by the vacuum energy density of a colored scalar field which is responsible for a phase transition in which the gauge SU(3)_c symmetry breaks.
We study the cosmological evolution of an induced gravity model with a self-interacting scalar field $sigma$ and in the presence of matter and radiation. Such model leads to Einstein Gravity plus a cosmological constant as a stable attractor among homogeneous cosmologies and is therefore a viable dark-energy (DE) model for a wide range of scalar field initial conditions and values for its positive $gamma$ coupling to the Ricci curvature $gamma sigma^{2}R$.
The non-commutative kappa-Minkowski field theory, often tauted as a low-energy candidate for the quantum description of gravity, operates on a spacetime which possesses a modified Lorentz invariance, and as such can be probed in high-precision low-energy experiments. We study the first order corrections in kappa to the Standard Model, and show that they typically induce a coupling of nuclear spin to an external background at low energies.
After introduction and motivation, I will present a covariant entropy bound conjecture on dynamical horizon in a general sense. Then I will show its validity in black hole case and cosmological context. Especially its power in constraint on the cosmological constant is addressed. I will end up with the outlook of this conjecture.
A new class of particle physics models of inflation is presented which is based on the phase transition associated with the spontaneous breaking of family symmetry responsible for the generation of the effective quark and lepton Yukawa couplings. We show
We point out that light scalar fields with symmetries generically generate non-Gaussianity in the density fluctuations. Our observation makes the presence of the non-Gaussianity ubiquitous. When the inflationary scale and the properties of the scalar fields satisfy a certain relation, the non-Gaussianity becomes large enough to be observed by the ongoing and planned observations. We name such a particle responsible for a large non-Gaussianity as an \'ungaussiton\', and give explicit examples to realize the ungaussiton mechanism.
One of the most compelling hints for physics beyond the standard model is the cosmological observation that nearly a quarter of our universe consists of cold dark matter. In the next few years, LHC shows the promise of producing these elusive particles and possibly measuring their microscopic properties. This will be challenging, per se, and using LHC observations to reconstruct a complete theory of cosmological dark matter could prove quite challenging. In this talk I will discuss the prospects and many challenges facing such a program.
We compute the GW signature of a meta-stable cosmic string network. Such networks arise in a large class of brane inflation models.
We formulate a general replica field-theoretic framework for stochastic inflation in which a manifestation of dimensional reduction is found. The scale above which the latter becomes dominant is explicitly calculated. It is found that for a wide class of stochastic systems considerable changes of the spectral index inevitably occur on super-horizon scales. We work out an explicit relation between the noise correlator and the non-Gaussianity parameter $f_{NL}$, which thus can effectively be generated entirely by quantum fluctuations.
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