Video Library

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. 

  

 

Monday Mar 17, 2014
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Central to quantum theory, the wavefunction is a complex distribution associated with a quantum system. Despite its fundamental role, it is typically introduced as an abstract element of the theory with no explicit definition. Rather, physicists come to a working understanding of it through its use to calculate measurement outcome probabilities through the Born Rule. Tomographic methods can reconstruct the wavefunction from measured probabilities.

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Friday Mar 14, 2014
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Superselection rules in quantum theory assert the impossibility of preparing coherent superpositions of certain conserved quantities. For instance, it is commonly presumed that there is a superselection rule for charge and for baryon number, as well as a "univalence superselection rule" forbidding a coherent superposition of a fermion and a boson. I will show how many superselection rules can be effectively lifted using a reference frame for the variable that is conjugate to the conserved quantity.

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Thursday Mar 13, 2014
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We argue that the infinite-dimensional BMS symmetry discovered by Bondi et. al in the 60s provides an exact symmetry of the quantum gravity S-matrix. The Ward identity of this symmetry is shown to be precisely Weinberg's soft graviton theorem, also discovered in the 60s. A parallel infinite-dimensional symmetry is found to be generated in nonabelian gauge theories by gauge transformations which go to an angle-dependent finite constant at null infinity. The Ward identity of this symmetry is shown to be the soft gluon theorem.

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