# 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.

## Higher-Order Quantum Computations

Tuesday Jun 02, 2009
Speaker(s):

TBA

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## Operational structures as a foundation for probabilistic theories

Tuesday Jun 02, 2009
Speaker(s):

Work on formulating general probabilistic theories in an operational context has tended to concentrate on the probabilistic aspects (convex cones and so on) while remaining relatively naive about how the operational structure is built up (combining operations to form composite systems, and so on). In particular, an unsophisticated notion of a background time is usually taken for granted. It pays to be more careful about these matters for two reasons. First, by getting the foundations of the operational structure correct it can be easier to prove theorems.

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## What is a quantal reality?

Monday Jun 01, 2009
Speaker(s):

I will rephrase the question, "What is a quantal reality?" as "What is a quantal history?" (the word history having here the same meaning as in the phrase sum-over-histories). The answer I will propose modifies the rules of logical inference in order to resolve a contradiction between the idea of reality as a single history and the principle that events of zero measure cannot happen (the Kochen-Specker paradox being a classic expression of this contradiction).

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## Complementarity as a resource

Monday Jun 01, 2009
Speaker(s):

TBA

Scientific Areas:

## Phase Groups and Complementarity

Monday Jun 01, 2009
Speaker(s):

TBA

Scientific Areas:

## Inhomogeneities in Loop Quantum Cosmology: The Gowdy Model

Thursday May 28, 2009

As a necessary step towards the extraction of realistic results from Loop Quantum Cosmology, we analyze the physical consequences of including inhomogeneities. We consider a gravitational model in vacuo which possesses local degrees of freedom, namely, the linearly polarized Gowdy cosmologies. We carry out a hybrid quantization which combines loop and Fock techniques.

Collection/Series:
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## The quantization of unimodular gravity and the cosmological constant problem

Wednesday May 27, 2009
Speaker(s):

TBA

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## Modifying Gravity in the Infra-Red by imposing an Ultra-Strong equivalence principle.

Wednesday May 27, 2009
Speaker(s):

I will give account of a work in progress in which I attempt to modify the metric-manifold structure of GR in the infra-red. The proposed modification does not contain any massive parameter as it is effective at length scales comparable with the inverse (extrinsic) curvature. The guiding line for this modification is an "ultra-strong" equivalence principle, according to which even semi-classical gravitational effects (i.e. particle production) are definitely banned from a sufficiently small free-falling elevator.

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## Using Large-Scale Structure and CMB Observations to Probe the Properties of Dark Energy

Wednesday May 27, 2009
Speaker(s):

Cosmologists are struggling to understand why the expansion rate of our universe is now accelerating. There are two sets of explanations for this remarkable observation: dark energy fills space or general relativity fails on cosmological scales. If dark energy is the solution to the cosmic acceleration problem, then the logarithmic growth rate of structure $dlnG/dlna = \Omega^\gamma$, where $\Omega$ is the matter density independent of scale in a dark matter plus dark energy model.

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## Gravitational aether as a solution to the CC problem and more!

Wednesday May 27, 2009
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## Next Public Lecture

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## RECENT PUBLIC LECTURE

### Mario Livio: Brilliant Blunders

Speaker: Mario Livio