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.
The k-essence theories admit the superluminal propagation of the perturbations on classical nontrivial backgrounds. In this talk I will review our arguments from arXiv:0708.0561v1 and show that in spite of the superluminal propagation the causal paradoxes do not arise in these theories and in this respect they are not less safe than General Relativity.
We investigate the effect of evaporating primordial black holes on the ionization history of the universe, with emphasis on limits derivable from the CMB and future 21-cm observations of high-redshift neutral hydrogen.
The cosmological power of Type Ia Supernovae depends on their ability to determine distances. The astrophysical limitations, like reddening, local velocity inhomogeneities and intrinsic variations, are a severe impediment for the cosmological applications of these cosmic explosions. Overcoming these systematic restrictions must be the goal of any future supernova projects.