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.
I will present Cosmological FRW Solutions in BiGravity Theories and discuss their stability. After deriving the stability bound, one realizes that in Bigravity (in contradistinction to the FRW massive gravity case) the tension between requirements stemming from stability and those set by observations is resolved. The stability bound can also be derived in the decoupling limit of Bigravity. In this context an intriguing duality between Galilean interactions has emerged.
In several approaches
to quantum-gravity, the spectral dimension of spacetime runs from the standard
value of 4 in the infrared (IR) to a smaller value in the ultraviolet (UV).
Describing this running in terms of deformed dispersion relations, I show that
a striking cosmological implication is that that UV behavior leading to 2
spectral dimensions results in an exactly scale-invariant spectrum of vacuum scalar
and tensor fluctuations. I discuss scenarios that break exact scale-invariance