Colloquium

614 talks

S001

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Displaying 349 - 360 of 614

Insightful supersymmetry

Erich Poppitz University of Toronto
November 27, 2013

PIRSA:13110061
Particle Physics
Light and matter: towards macroscopic quantum systems

Jacob Taylor Office of Science and Technology Policy
November 20, 2013

PIRSA:13110060
Quantum Information
Spin and Long-Range Forces: The Unfinished Tale of the Last Massless Particle

Natalia Toro Stanford University
November 13, 2013

PIRSA:13110047
Particle Physics
Fractional statistics in two-dimensions: Anyon there?

Smitha Vishveshwara University of Illinois Urbana-Champaign
November 06, 2013

PIRSA:13110062
Mathematical physics
Gravity and the Search for New Physics with Cosmology

Kris Sigurdson University of British Columbia
October 30, 2013

PIRSA:13100098
Particle Physics
The Stokes groupoids

Marco Gualtieri University of Toronto

October 23, 2013

PIRSA:13100110
Simulating Hamiltonian evolution with quantum computers

Richard Cleve Institute for Quantum Computing (IQC)
October 16, 2013

PIRSA:13100097
Quantum Information
From Supersolidity to Giant Plasticity: Defects in Quantum Crystals

John Beamish University of Alberta
October 09, 2013

PIRSA:13100065
Condensed Matter
Alan Turing and the Enigma Machine

James Grime University of Cambridge

October 02, 2013

PIRSA:13100079
Slippery Waves: Brilliance Brings Blind Spots

Leo Kadanoff
September 25, 2013

PIRSA:13090051
Mathematical physics
Short Gamma-Ray Bursts and the Electromagnetic Counterparts of Gravitational Wave Sources

Edo Berger Harvard University

September 18, 2013

PIRSA:13090050
The Era of Three Generations: Possible hints from neutrinos in elucidating the matter/antimatter asymmetry of the Universe
September 11, 2013

PIRSA:13090065
Particle Physics

Insightful supersymmetry

Erich Poppitz University of Toronto
November 27, 2013

PIRSA:13110061
Particle Physics
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 be seen to be the major players in the confinement-deconfinement dynamics. Interesting connections between topology, ``condensed-matter" gases of electric and magnetic charges, and attempts to interpret the divergent perturbation series will emerge. Much of the presentation will be aimed at non-experts.
Light and matter: towards macroscopic quantum systems

Jacob Taylor Office of Science and Technology Policy
November 20, 2013

PIRSA:13110060
Quantum Information
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. Furthermore, I will highlight practical consequences of these advances, including improved force and acceleration sensing, efficient signal transduction, and topologically robust photonic circuits. Finally, I will consider how such large quantum systems may help us measure and constrain theories of quantum gravity and gravity-induced decoherence.
Spin and Long-Range Forces: The Unfinished Tale of the Last Massless Particle

Natalia Toro Stanford University
November 13, 2013

PIRSA:13110047
Particle Physics
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. I will explain recent progress in understanding these particles on two fronts: simple scattering amplitudes and a free quantum field theory. The scattering amplitudes give two remarkable insights into CSP physics. First, Lorentz symmetry protects CSP interactions from the dysfunction one might expect in a theory with infinitely many polarization states: divergent cross-sections and problematic thermodynamics. Second, and most intriguingly, CSP interactions approach those of ordinary scalars or helicity-1 or 2 gauge bosons in a high-energy "correspondence" regime. While a full interacting theory of CSPs remains elusive, these results suggest that any such theory would extend Maxwell electrodynamics and/or general relativity in a viable and testable way.
Fractional statistics in two-dimensions: Anyon there?

Smitha Vishveshwara University of Illinois Urbana-Champaign
November 06, 2013

PIRSA:13110062
Mathematical physics
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, drawing from analogies with the bosonic behavior of light studied by Hanbury Brown and Twiss in the 1950's as well as in the more recent beam-splitter settings in quantum optics. Finally, the exciting prospect of detecting fractional statistics in the context of superconductors will be explored.
Gravity and the Search for New Physics with Cosmology

Kris Sigurdson University of British Columbia
October 30, 2013

PIRSA:13100098
Particle Physics
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. Eighty years ago gravity betrayed the existence of dark matter, and fifteen years ago gravity demanded dark energy from reluctant cosmologists. I will discuss how gravity enables modern cosmology to explore the echoes of the invisible universe, even if it is impossible or difficult to directly see the invisible universe. In particular, I will show how gravity enables us to put surprisingly severe constraints on the coupling of dark matter to new light particles and search for secret interactions between Fermi's elusive neutrinos. The physics and cosmic history of the invisible universe are writ large across the cosmos itself, and gravity is our tried and trusted messenger.
The Stokes groupoids

Marco Gualtieri University of Toronto

October 23, 2013

PIRSA:13100110

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. The asymptotic interpretation of this divergent series exhibits the famous Stokes phenomenon, an essential ingredient in any full description of the solutions to the system. I will explain a new viewpoint on singular ODE which illuminates the geometric meaning of the phenomena described above, and which can be applied to the problem of resummation of formal power series. This viewpoint uses a very basic but underused tool in differential geometry: Lie groupoids. A Lie groupoid is as natural and essential an object as a Lie group; I shall explain how to build examples of them and how to use them to solve singular differential equations.
Simulating Hamiltonian evolution with quantum computers

Richard Cleve Institute for Quantum Computing (IQC)
October 16, 2013

PIRSA:13100097
Quantum Information
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.
From Supersolidity to Giant Plasticity: Defects in Quantum Crystals

John Beamish University of Alberta
October 09, 2013

PIRSA:13100065
Condensed Matter
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, amplitude and 3He impurity concentration as the torsional oscillator anomaly. These shear modulus changes are due to dislocations and their interactions with impurities and vacancies. Our experiments raised an obvious question – could the torsional oscillator behavior be an artifact of the elastic changes, rather than evidence of supersolidity? During the past two years it has become clear that the answer is “yes” and interest has focused on the properties of dislocations in a quantum solid like 4He. By growing high quality single crystals in optical cells, we have now been able to explore the behavior of dislocations in 4He in unprecedented detail. In some crystals the dislocations reduce the shear modulus by more than 80%, an extraordinary effect we describe as “giant plasticity”. Solid helium has proved to be an ideal system in which to do materials science, as well as to address fundamental questions about quantum solids.
Alan Turing and the Enigma Machine

James Grime University of Cambridge

October 02, 2013

PIRSA:13100079

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 an original WWII Enigma Machine!
Slippery Waves: Brilliance Brings Blind Spots

Leo Kadanoff
September 25, 2013

PIRSA:13090051
Mathematical physics
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 fraction of the particles in the system. Superfluidity can then be understood in terms of the wave function for this configuration, which necessarily extends over a finite fraction of the system. Neither blockbuster paper mentions Einstein or the crucial idea of a condensate wave function. The reasons for this omission are mooted.
Short Gamma-Ray Bursts and the Electromagnetic Counterparts of Gravitational Wave Sources

Edo Berger Harvard University

September 18, 2013

PIRSA:13090050

Gamma-ray bursts are the most luminous and energetic explosions known in the universe. They appear in two varieties: long- and short-duration. The long GRB result from the core-collapse of massive stars, but until recently the origin of the short GRBs was shrouded in mystery. In this talk I will present several lines of evidence that point to the merger of compact objects binaries (NS-NS and/or NS-BH) as the progenitor systems of short GRBs. Within this framework, the observational data also allow us to independently determine the merger rate of these systems as input to the Advanced LIGO event rate, to infer the merger distribution timescale, and to determine the energy scale of the mergers. In addition, using radio to X-ray observations of short GRBs we can determine the expected electromagnetic properties of Advanced LIGO sources.
The Era of Three Generations: Possible hints from neutrinos in elucidating the matter/antimatter asymmetry of the Universe
September 11, 2013

PIRSA:13090065
Particle Physics
Despite being one of the most abundant constituents of the Universe and more than a half a century of study, some of the most fundamental properties of the neutrino have only been recently uncovered, and others still remain unresolved. I will discuss important developments in the phenomenon of neutrino oscillations, a transmutation process that allows neutrinos to change between three types as they propagate in time. In particular, recent discoveries have opened up the possibility of CP violation in neutrino oscillations, asymmetries in the behavior of neutrinos and their anti-matter counterparts. CP violation, along with other unresolved properties of the neutrino, may play a central role in how the universe came to a matter-dominated state. I will also discuss a new generation of experiments that may allow us to establish whether CP violation does indeed occur in neutrino oscillations.

Title	Speaker(s)	Date	Talk Type	Info
Insightful supersymmetry	Erich Poppitz	2013-11-27	Scientific Series	View details
Light and matter: towards macroscopic quantum systems	Jacob Taylor	2013-11-20	Scientific Series	View details
Spin and Long-Range Forces: The Unfinished Tale of the Last Massless Particle	Natalia Toro	2013-11-13	Scientific Series	View details
Fractional statistics in two-dimensions: Anyon there?	Smitha Vishveshwara	2013-11-06	Scientific Series	View details
Gravity and the Search for New Physics with Cosmology	Kris Sigurdson	2013-10-30	Scientific Series	View details
The Stokes groupoids	Marco Gualtieri	2013-10-23	Scientific Series	View details
Simulating Hamiltonian evolution with quantum computers	Richard Cleve	2013-10-16	Scientific Series	View details
From Supersolidity to Giant Plasticity: Defects in Quantum Crystals	John Beamish	2013-10-09	Scientific Series	View details
Alan Turing and the Enigma Machine	James Grime	2013-10-02	Scientific Series	View details
Slippery Waves: Brilliance Brings Blind Spots	Leo Kadanoff	2013-09-25	Scientific Series	View details
Short Gamma-Ray Bursts and the Electromagnetic Counterparts of Gravitational Wave Sources	Edo Berger	2013-09-18	Scientific Series	View details
The Era of Three Generations: Possible hints from neutrinos in elucidating the matter/antimatter asymmetry of the Universe		2013-09-11	Scientific Series	View details

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