# Video Library

Since 2002 Perimeter Institute has been recording seminars, conference talks, public outreach events such as talks from top scientists 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 and 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.

Accessibly by anyone with internet, Perimeter aims to share the power and wonder of science with this free library.

## The Cohomology of Groups (Johnson-Freyd/Guo) - Lecture 11

Friday Dec 13, 2019
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## Closing Discussion Session

Friday Dec 13, 2019
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## TBA

Friday Dec 13, 2019
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## Causality in Qbism

Friday Dec 13, 2019
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The approach to quantum theory known as QBism notoriously asserts that the quantum state is not even a partial representation of reality, but instead quantifies an agent's subjective degrees of belief about future experiences. Despite its counter-intuitive premise, QBists argue that this interpretation has the potential to illuminate and demystify certain aspects of quantum theory. In this talk I will discuss how causality' might be interpreted by a QBist, and whether doing so might help us understand the bizarre hypothetical phenomenon of indefinite causality'.

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## Discussion Session 2

Thursday Dec 12, 2019
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## TBA

Thursday Dec 12, 2019
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## Indefinite causal order without post-selection

Thursday Dec 12, 2019
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The possibility of indefinite causal order has garnered considerable interest in recent years, both for its promise as a resource, e.g. for communication, and for its role in exploring the fundamental physical constraints on causal structure. In order to gain a better understanding of the phenomenon, one approach is to design experiments that implement – or at least simulate – scenarios with indefinite causal order. While post-selection is one way to simulate exotic causal structures, this approach may not provide the desired insights.

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## Deciphering the Landscape of Binary Black Hole Formation Channels

Thursday Dec 12, 2019
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Merging compact objects encode a vast deal of information about their progenitor stellar systems, such as the types of galactic environments they were born in, the intricacies of stellar evolution the persisted throughout their lives, and the physics of the supernovae that marked their deaths. In this talk, I will highlight multiple open questions that can be illuminated through a combination of compact objects observations (via gravitational waves and/or electromagnetic radiation) and computational modeling of environments that lead to the formation of black holes and neutron stars.

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## TBA

Thursday Dec 12, 2019
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## Time reference frames and gravitating quantum clocks

Thursday Dec 12, 2019
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The standard formulation of quantum theory relies on a fixed space-time metric determining the localisation and causal order of events. In general relativity, the metric is influenced by matter, and it is expected to become indefinite when matter behaves quantum mechanically. Here we explore the problem of operationally defining events and their localisation in the presence of gravitating quantum systems. We develop a framework for "time reference frames," in which events are defined in terms of quantum operations with respect to a quantum clock.

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## Lectures On-Demand

Watch on Perimeter's