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.
Matrix Product States (MPS) and their higher dimensional extensions, the Projected Entangled-Pair States (PEPS) can efficiently describe the ground and thermal states of interacting systems with short-range interactions. We will describe some mathematical properties of this families of states, as well as possible extensions. Work in collaboration with N. Schuch, D. Perez-Garcia, M. Sanz, M. Wolf, F. Verstraete and G. Sierra.