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.
Maximizing the science return on the Event Horizon Telescope project requires fitting models for spatially resolved black hole images to the data. These images can be calculated from accretion and jet theory, but theoretical uncertainties lead to systematic errors in the predicted images. In many cases, however, the images are dominated by the combined effects of Doppler beaming and light bending, leading to a characteristic “crescent” shape. I will discuss a geometric crescent model for black hole images based on these effects.
We are now two years into development of hardware and software for phasing ALMA, with emphasis on Band 6 (1.2 mm) but applicability to bands 3 and 7. Central to the effort is software to continuously calculate and apply a phasing solution, and the hardware interface cards (PIC) and other upgrades to the correlator that apply the solution, format the data and extract the correlated data stream. Upstream from the correlator is a hydrogen maser, which is the new ALMA time standard.
Over the next few years the Event Horizon Telescope will greatly expand its capabilities from the current 8 Gbps at a few sites to 64 Gbps at a much larger number of sites. The good news is that this processing can proceed through 4 independent (16 Gbps) processing stages of 2 GHz of bandwidth. The bad news is that EHT stations come in multiple "flavors" each posing its own issues for correlation with DiFX (the current correlation option). This talk will discuss some of the issues and the road ahead.
It is by now well established that black holes emit a thermal radiation and undergo an evaporation process. The original Hawking evaporation scenario, based on quantum fields on a classical background geometry, has been vastly extended and improved, in order to take into account in particular the backreaction of the radiation on the geometry. This can be done for example in a semiclassical setup, where the Einstein equations are sourced by an effective stress energy tensor.
The EHT data acquisition campaign in March 2015 will utilize new digital backends on many of the new and existing sites. We will briefly overview the state of the art for wideband digital backends for VLBI and discuss the several flavors that will be employed this coming year. Specifically, we will focus on details of the Roach2 Digital Backend (R2DBE), a new 16 Gbps wideband DBE unit that can be scaled to 64 Gbps, to be employed at single dish sites.
We are investigating modifications of general relativity that are operative at the largest observable scales. In this context, we are investigating the model of brane induced gravity in 6D, a higher dimensional generalization of the DGP model. As opposed to different claims in the literature, we have proven the quantum stability of the theory in a weakly coupling regime on a Minkowski background. In particular, we have shown that the Hamiltonian of the linear theory is bounded from below. This result opened a new window of opportunity for consistent modified Friedmann cosmologies.
The path from the current EHT to the full array capabilities has been mapped out over the past several years. Through the efforts of the EHT Technical Working Group and the full complement of experts involved in the project, we have a detailed plan and work breakdown to implement these improvements. I will describe the schedule for EHT expansion and enhancement from 2015 onward.