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.
In this talk I will analyse the stochastic background of gravitational waves coming from a first order phase transition in the early universe. The signal is potentially detectable by the space interferometer LISA. I will present a detailed analytical model of the gravitational wave production by the collision of broken phase bubbles, together with analytical results for the gravitational wave power spectrum. Gravitational wave production by turbulence and magnetic fields will also be briefly discussed.
We discuss recent developments in the study of black holes and similar compact objects in string theory. The focus is on how these solutions are effected by higher-derivative terms in an effective action. The setting of this investigation is an off-shell formulation of five-dimensional supergravity, including terms of order four-derivatives whose precise form are determined by embedding this theory in M-theory.
Many numerical studies show that dark matter halos have a plethora of substructure, down to the smallest resolved scales. However, the very bottom of the Cold Dark Matter (CDM) hierarchy at a few earth masses, where the spectral index n approaches -3 and structure begins to form simultaneously on a variety of scales, remains relatively unexplored. It is possible that the subhalo mass distribution, which appears to be described by a simple power-law down to mass scales 10^6 solar masses, remains unchanged and independent of scale and n.