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.
A modification of Gravity in the low-curvature regime may account for the late time acceleration of our universe, and is therefore an interesting alternative to Dark Energy.In such models, the modified Einstein equations admit self-accelerated solutions in the presence of negligible matter. At the level of perturbation theory,the modified equations give rise to new dynamics for the perturbations of the metric and matter.
I will present the embedding of runaway quintessence models in supergravity coupled to observable matter and hidden supersymmetry breaking. Serious obstructions appear either in the gravitational sector of the theory or cosmologically. Alternatives will be discussed.
We explore the hypothesis that a dynamical dark energy is related to a time-variation of the fundamental mass scale. A dilatation anomaly induced by quantum fluctuations could explain the small value of the present dark energy. Reformulated as a scalar field theory this would predict a quintessence potential which asymptotically relaxes to zero rather than to a nonvanishing constant. An observable consequence of such a scenario results in "early dark energy " contributing a few percent to the energy density of the Universe even at high redshift.
In nearly every quantum algorithm which exponentially outperforms the best classical algorithm the quantum Fourier transform plays a central role. Recently, however, cracks in the quantum Fourier transform paradigm have begun to emerge. In this talk I will discuss one such development which arises in a new efficient quantum algorithm for the Heisenberg hidden subgroup problem.