# Colloquium

This series covers all areas of research at Perimeter Institute, as well as those outside of PI's scope.

## Seminar Series Events/Videos

Currently there are no upcoming talks in this series.

## Insightful supersymmetry

Wednesday Nov 27, 2013
Speaker(s):

It has
recently been realized that some studies of supersymmetric gauge theories, when
properly interpreted, lead to insights whose importance transcends
supersymmetry. I will illustrate the insightful nature of supersymmetry by two
examples having to do with the microscopic description of the thermal
deconfinement transition, in non-supersymmetric pure Yang-Mills theory and in
QCD with adjoint fermions. A host of strange topological" molecules will

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## Light and matter: towards macroscopic quantum systems

Wednesday Nov 20, 2013
Speaker(s):

Advances in quantum engineering and material science are enabling new approaches for building systems that behave quantum mechanically on long time scales and large length scales. I will discuss how microwave and optical technologies in particular are leading to new domains of many-body physics, both classical and quantum, using photons and phonons as the constituent particles.

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## Spin and Long-Range Forces: The Unfinished Tale of the Last Massless Particle

Wednesday Nov 13, 2013
Speaker(s):

The success of gauge theory descriptions of Nature follows simply, in hindsight, from Lorentz symmetry, quantum mechanics, and the existence of interacting massless particles with spin. Yet, remarkably, the most generic type of massless particle spin has never been seriously examined: Wigner's so-called "continuous spin" particles (CSPs), which have a tower of polarization states carrying all integer or half-integer helicities that mix under boosts.

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## Fractional statistics in two-dimensions: Anyon there?

Wednesday Nov 06, 2013
Speaker(s):

A fascinating aspect of the two dimensional
world is the possible existence of anyons, particles which obey 'fractional'
statistics different from fermionic and bosonic statistics. In this colloquium,
following an introduction to fractional particles in the context of quantum
Hall systems, some of the tantalizing experiments for detecting the fractional
charge of these particles will be described.
Probes of fractional statistics in these systems will be discussed,

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## Gravity and the Search for New Physics with Cosmology

Wednesday Oct 30, 2013
Speaker(s):

Despite its feeble in strength, gravity plays a pivotal role in shaping our Universe and the things in it. Ever since Newton formulated his universal law of gravitation the recognition that all things gravitate has been nearly sacrosanct. Repeatedly, apparent gravitational anomalies have either foretold the existence of new physics or a misunderstanding of gravity itself, from the existence of nuclear forces to Einstein's general relativity.

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## The Stokes groupoids

Wednesday Oct 23, 2013
Speaker(s):

Ordinary differential equations become much less ordinary
when they are allowed to have singularities.
Solving them naively in formal power series, one often obtains divergent
series, just as in the perturbation series for physical observables in quantum
field theory.

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## Simulating Hamiltonian evolution with quantum computers

Wednesday Oct 16, 2013
Speaker(s):

In 1982, Richard Feynman proposed the concept of a quantum computer as a means of simulating physical systems that evolve according to the Schrödinger equation. I will explain various quantum algorithms that have been proposed for this simulation problem, including my recent work (jointly with Dominic Berry and Rolando Somma) that significantly improves the running time as a function of the precision of the output data.

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## From Supersolidity to Giant Plasticity: Defects in Quantum Crystals

Wednesday Oct 09, 2013
Speaker(s):

In 2004, Kim and Chan reported torsional
oscillator experiments on 4He crystals which showed evidence of
“non-classical rotational inertia”, the mass decoupling expected for a
long-sought “supersolid” state. It soon
became clear that this behavior is not a property of perfect crystals – defects
are involved. In 2007, we made elastic
measurements which showed, to our surprise, that the shear modulus of solid 4He
increases dramatically below 0.2 K, with the same dependence on temperature,

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## Alan Turing and the Enigma Machine

Wednesday Oct 02, 2013
Speaker(s):

Alan Turing was one of our great 20th century
mathematicians, and a pioneer of computer science. However, he may best be
remembered as one of the leading code breakers of Bletchley Park during World
War II. It was Turing's brilliant insights and mathematical mind that helped to
break Enigma, the apparently unbreakable code used by the German military. We
present a history of both Alan Turing and the Enigma, leading up to this
fascinating battle of man against machine - including a full demonstration of

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## Slippery Waves: Brilliance Brings Blind Spots

Wednesday Sep 25, 2013
Speaker(s):

Superfluidity and superconductivity are two remarkable
phenomena in which, at low temperatures, materials abruptly gain the ability to
flow without friction. Microscopic quantum theories of these phases of matter
were constructed in blockbuster papers of Lev Landau (1940) and John Bardeen,
Leon Cooper, and J. Robert Schrieffer
(1957). The actual explanation of
the flow, however, is rooted in a
Einstein paper of 1924 that introduces a condensate, a quantum configuration describing a finite

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## RECENT PUBLIC LECTURE

### Mario Livio: Brilliant Blunders

Speaker: Mario Livio