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 describe the Dark Energy Spectroscopic Instrument (DESI), an instrument currently being built to carry out a large galaxy redshift survey. DESI is the next step beyond the SDSS and BOSS surveys, mapping over 30 million galaxies. I will focus in particular on the amazing engineering challenges of the DESI instrument itself, which includes a 5,000-robot army and 250 kilometers of fiber optics. I will conclude by briefly describing the work I am personally involved in: a large imaging survey that will measure the galaxies from which DESI will select targets for
An F-field on a manifold M is a local system of algebraically closed fields of characteristic p. You can study local systems of vector spaces over this local system of fields. On a 3-manifold, they are are rigid, and the rank one local systems are counted by the Alexander polynomial. On a surface, they come in positive
Modified gravitation known as Scalar-Tensor- Vector-Gravity (STVG) and MOG and its consequences for dark matter and dark energy in astrophysics and cosmology and black holes is reviewed. A variable speed of light (VSL) cosmology is compared to inflation.
The conformal bootstrap aims to calculate scaling dimensions and correlation functions in various theories, starting from general principles such as unitarity and crossing symmetry. I will explain that local operators are not independent of each other but organize into analytic functions of spin, and I will present a formula which quantifies the consequences of this fact.
Just like how milli-electric charged particles can exist, so can milli-magnetic charged particles. We review simple ways of evading the standard quantization arguments and why there are no model independent constraints on magnetically charged particles, milli-charged or not. We then provide the first ever model independent bounds coming from magnetar cooling arguments.
We define an action of the k-strand braid group on the set of cluster variables for the Grassmannian Gr(k,n), provided k divides n. The action sends clusters to clusters, preserving the underlying quivers, defining a homomorphism from the braid group to the cluster modular group for Gr(k,n). Our results can be translated to statements about clusters in Fock-Goncharov configuration spaces of affine flags, provided the number of flags is even.