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 gauge/gravity enables us to learn about quantum gravity by solving gauge theory. This is not an easy task, of course, and hence numerical techniques should play important roles. So far, properties of super Yang-Mills theories with Euclidean signature, such as the thermodynamic properties, have been studied by using Monte Carlo methods, and good agreement with the dual gravity prediction has been observed, including stringy corrections, both alpha prime and and g_s. Still, the real-time properties are not well understood.
It is an attractive idea that effective theories admitting a consistent UV completion require quanta to propagate sub-luminally in non-trivial backgrounds.
I will discuss the Vainshtein mechanism in massive gravity. I will show that the spherically symmetric backgrounds that were believed to have superluminal sound speed are in fact unstable. Instead, there is a new class of phenomenologically relevant solutions with stable and subluminal perturbations.