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 causal set -- mathematically a finitary partial order -- is a candidate discrete substratum for spacetime. I will introduce this idea and describe some aspects of causal set kinematics, dynamics, and phenomenology, including, as time permits, a notion of fractal dimension, a (classical) dynamics of stochastic growth, and an idea for explaining some of the puzzling large numbers of cosmology. I will also mention some general insights that have emerged from the study of causal sets, the most recent one concerning the role of intermediate length-scales in discrete spacetime theories.
Einsteins profound ideas about relativity and the quantum have provided generations of people with some of the most thought-provoking concepts ever proposed about the wonders and mysteries of our universe. This lively panel discussion will examine Einsteins enormous contributions to our understanding.
We point out that there exit operators, having a clear meaning in cosmology -- they select a given realization of the distribution of primordial density fluctuations --, which can violate Bell inequalities when evaluated in the ''standard'' inflationary quantum distribution. We then consider density matrices which describe partially decohered distributions and show how the importance of the violation decreases with the decoherence level. We determine the critical level beyond which no violation can be obtained.