# 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.

## PSI 2019/2020 - Gravitational Physics - Lecture 2

Tuesday Jan 07, 2020
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## PSI 2019/2020 - Quantum Matter Part 1 - Lecture 2

Tuesday Jan 07, 2020
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## PSI 2019/2020 - Standard Model and Beyond - Part 1 - Lecture 1

Monday Jan 06, 2020
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## PSI 2019/2020 - Gravitational Physics - Lecture 1

Monday Jan 06, 2020
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## PSI 2019/2020 - Quantum Matter Part 1 - Lecture 1

Monday Jan 06, 2020
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## Unitarization from geometry

Tuesday Dec 17, 2019
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Scattering amplitudes of massive spin-2 particles generically grow with energy and lead to violations of perturbative unitarity. One way to partially soften such amplitudes is with the infinite towers of particles present in Kaluza-Klein theories. In this talk I will discuss in detail this mechanism of unitarization for general dimensional reductions of pure gravity and show that it leads to some interesting constraints on the eigenfunctions and eigenvalues of the scalar Laplacian on closed manifolds.

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## 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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## Lectures On-Demand

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