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.
Understanding NP-complete problems is a central topic in computer science. This is why adiabatic quantum optimization has attracted so much attention, as it provided a new approach to tackle NP-complete problems using a quantum computer. The efficiency of this approach is limited by small spectral gaps between the ground and excited states of the quantum computer's Hamiltonian.
We introduce a class of probability spaces whose objects are infinite graphs and whose probability distributions are obtained as limits of distributions for finite graphs. The notions of Hausdorff and spectral dimension for such ensembles are defined and some results on their value in koncrete examples, such as random trees, will be described.
Using a formulation of the post-Newtonian expansion in terms of Feynman graphs, we discuss how various tests of General Relativity (GR) can be translated into measurement of the three- and four-graviton vertices. The timing of the Hulse-Taylor binary pulsar provides a bound on the deviation of the three-graviton vertex from the GR prediction at the 0.1% level.
While gravitational waves offer a new, and in many ways clean, view of compact objects, most of what we presently know about these has been obtained by careful study of their messy interactions with surrounding material. I will summarize what we know about a variety of potential gravitational wave sources, how this astrophysical hair has helped to illuminate some of the same questions gravitational wave observations promise to address, and how future observations may begin to relate the gravitational and electromagnetic properties of compact objects.
In addition to the dominant oscillatory modes gravitational waves contain non-oscillatory components which arise as drifts or offsets in the signals. Nonlinear gravitational memory arises from a change in mass multipole moments of a boundsystem due to contributions from the emitted gravitationalwaves. In practice it appears as a slowly monotonically growingsignal during the inspiral which sees a rapid rise at thetime of merger.
We present a short overview on the current state of core-collapse supernova modeling and the set of processes expected to emit gravitational waves in a core collapse event. We go on to show new results from 3D GR simulations focusing on failing black-hole forming supernovae and present the gravitational wave signature of such events.
In this work we investigate the electromagnetic radiation induced by a binary black hole merger when they are surrounded by a force-free environment (i.e. plasma with inertia terms negligible compared to the electromagnetic stresses). We discuss the relevance of this system for possible multimessenger astronomy with binary black holes.
I will report on some recent results obtained using the fully general relativistic magnetohydrodynamic code Whisky in simulating equal and unequal-mass binary neutron star (BNS) systems during the last phases of inspiral, merger and collapse to black hole surrounded by a torus.