# Video Library

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.

## Higgs sheaves on a curve and Cohomological Hall algebras

Thursday Feb 16, 2017
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Cohomological Hall algebras associated with preprojective algebras of quivers play a preeminent role in geometric representation theory and mathematical physics. In the present talk, I will introduce and describe CoHAs associated with the stack of Higgs sheaves on a smooth projective curve. Moreover, I will address the connections with representation theory and gauge theory. (This is a joint work with Olivier Schiffmann.)

Scientific Areas:

## PSI 2016/2017 Quantum Field Theory III - Lecture 14

Thursday Feb 16, 2017
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## How I learned to stop worrying and to love both instantons and anti-instantons

Thursday Feb 16, 2017
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Scientific Areas:

## PSI 2016/2017 Cosmology (Review) - Lecture 13

Thursday Feb 16, 2017
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Scientific Areas:

## Geometric interpretation of Witten's d-bar equation

Thursday Feb 16, 2017
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The Witten d-bar equation is a generalization of the parametrized holomorphic curve equation associated to a holomorphic function (superpotential) on a Kahler manifold X. It plays a central role in the work of Gaiotto-Moore-Witten on the "algebra of the infrared".

The talk will explain an "intrinsic" point of view on the equation as a condition on a real surface S embedded into X (i.e., not involving any parametrization of S). This is possible if S is not a holomorphic curve in the usual sense.

Scientific Areas:

## PSI 2016/2017 Quantum Field Theory III - Lecture 13

Thursday Feb 16, 2017
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## The Hitchin system, past and present

Wednesday Feb 15, 2017
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The talk will be a survey of Higgs bundles, their moduli spaces and the associated fibration structure from a historical, and personal, point of view.

Scientific Areas:

## PSI 2016/2017 Quantum Field Theory III - Lecture 12

Wednesday Feb 15, 2017
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## Symplectic geometry related to G/U and Sicilian theories'

Wednesday Feb 15, 2017
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We construct an action of the Weyl group on the affine closure of the cotangent bundle on G/U. The construction involves Hamiltonian reduction with respect to the universal centralizer' and an interesting Lagrangian variety, the Miura variety. A closely related construction produces symplectic manifolds which play a role in `Sicilian theories' and whose existence was conjectured by Moore and Tachikawa. Some of these constructions may be reinterpreted, via the Geometric Satake, in terms of the affine grassmannian.

Scientific Areas:

## 2016/2017 Statistical Mechanics 2 - Roger Melko - Lecture 13

Wednesday Feb 15, 2017
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## Next Public Lecture

### EUGENIA CHENG: HOW TO BAKE PI

Wednesday Apr 05, 2017

## RECENT PUBLIC LECTURE

### Amber Straughn: A New Era in Astronomy: NASA’s James Webb Space Telescope

Speaker: Amber Straughn