Talks

10129 - 10140 of 16890 Results

From Supersolidity to Giant Plasticity: Defects in Quantum Crystals

John Beamish University of Alberta

October 09, 2013

PIRSA:13100065

Condensed Matter
13/14 PSI - Statistical Mechanics - Lecture 3

Anton Burkov University of Waterloo

October 09, 2013

PIRSA:13100041
Topics in QFT on Flat and Curved Spacetimes - Lecture 6

Ugo Moschella University of Insubria

October 09, 2013

PIRSA:13100016
General Relativity for Cosmology - Lecture 4

Achim Kempf University of Waterloo

October 08, 2013

PIRSA:13100100
General Relativity for Cosmology - Lecture 3

Achim Kempf University of Waterloo

October 08, 2013

PIRSA:13100002
13/14 PSI - Quantum Field Theory I - Lecture 2

Freddy Cachazo Perimeter Institute for Theoretical Physics

October 08, 2013

PIRSA:13100021
A Nearly Gaussian Hubble-patch in a non-Gaussian Universe

Marilena LoVerde University of Washington

October 08, 2013

PIRSA:13100076

Cosmology
13/14 PSI - Statistical Mechanics - Lecture 2

Anton Burkov University of Waterloo

October 08, 2013

PIRSA:13100040
Geometry and Topology in the Fractional Quantum Hall Effect

Duncan Haldane Princeton University

October 07, 2013

PIRSA:13100086

Condensed Matter
13/14 PSI - Quantum Field Theory I - Lecture 1

Freddy Cachazo Perimeter Institute for Theoretical Physics

October 07, 2013

PIRSA:13100020
13/14 PSI - Statistical Mechanics - Lecture 1

Anton Burkov University of Waterloo

October 07, 2013

PIRSA:13100039
Topics in QFT on Flat and Curved Spacetimes - Lecture 5

Ugo Moschella University of Insubria

October 07, 2013

PIRSA:13100011

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.
13/14 PSI - Statistical Mechanics - Lecture 3

Anton Burkov University of Waterloo

October 09, 2013

PIRSA:13100041
Topics in QFT on Flat and Curved Spacetimes - Lecture 6

Ugo Moschella University of Insubria

October 09, 2013

PIRSA:13100016
General Relativity for Cosmology - Lecture 4

Achim Kempf University of Waterloo

October 08, 2013

PIRSA:13100100
General Relativity for Cosmology - Lecture 3

Achim Kempf University of Waterloo

October 08, 2013

PIRSA:13100002
13/14 PSI - Quantum Field Theory I - Lecture 2

Freddy Cachazo Perimeter Institute for Theoretical Physics

October 08, 2013

PIRSA:13100021
A Nearly Gaussian Hubble-patch in a non-Gaussian Universe

Marilena LoVerde University of Washington

October 08, 2013

PIRSA:13100076

Cosmology

Local-type primordial non-Gaussianity couples statistics of the curvature perturbation \zeta on vastly different physical scales. Because of this coupling, statistics (i.e. the polyspectra) of \zeta in our Hubble volume may not be representative of those in the larger universe -- that is, they may be biased. The bias depends on the local background value of \zeta, which includes contributions from all modes with wavelength k ~< H_0 and is therefore enhanced if the entire post-inflationary patch is large compared with our Hubble volume. I will discuss the bias to locally-measured statistics for general local-type non-Gaussianity. I will discuss three examples in detail: (i) the usual fNL, gNL model, (ii) a strongly non-Gaussian model with \zeta ~ \zeta_G^p, and (iii) two-field non-Gaussian initial conditions. In each scenario one may generate statistics in a Hubble-size patch that are weakly Gaussian and consistent with observations despite the fact that the statistics in the larger, post-inflationary patch look very different. Finally, I will present a worked example of how the variation in local statistics arises in the curvaton scenario.
13/14 PSI - Statistical Mechanics - Lecture 2

Anton Burkov University of Waterloo

October 08, 2013

PIRSA:13100040
Geometry and Topology in the Fractional Quantum Hall Effect

Duncan Haldane Princeton University

October 07, 2013

PIRSA:13100086

Condensed Matter

The FQHE is exhibited by electrons moving on a 2D surface through which a magnetic flux passes, giving rise to flat bands with extensive degeneracy (Landau levels). The degeneracy of a partially-filled Landau level is lifted by Coulomb repulsion between the electrons, which at certain rational fillings, leads to gapped incompressible topologically-ordered fluid states exhibiting the FQHE. Successful model wavefunctions for FQHE states, such as the Laughlin and Moore-Read states, are surprisingly related to Euclidean conformal field theory, even though they are gapped incompressiible quantum fluids with a fundamental unit of area set by the area per magnetic flux quantum h/e. The model wavefunctions are parametrized by a continuously-variable Euclidean metric, just like the Euclidean conformal group of the cft to which they are related. This metric is fixed locally both by the form of the projected Coulomb interaction within the partially-filled Landau level, and by local gradients of the tangential electric field on the 2D surface, promoting it from a static flat metric fixed globally by the cft, to a dynamic local physical degree of freedom of the FQHE fluid with area-preserving zero-point fluctuations that leave an imprint in the ground-state structure function. The curious connection to cft appears to be that the Virasoro algebra plays a fundament role in both cft and FQHE, for apparently-unrelated reasons. In the FQHE it derives from a chiral "gravitional" (geometric) topologically-protected anomaly at the edge of the fluid that is also revealed in the entanglement spectrum of a cut through the bulk fluid.
13/14 PSI - Quantum Field Theory I - Lecture 1

Freddy Cachazo Perimeter Institute for Theoretical Physics

October 07, 2013

PIRSA:13100020
13/14 PSI - Statistical Mechanics - Lecture 1

Anton Burkov University of Waterloo

October 07, 2013

PIRSA:13100039
Topics in QFT on Flat and Curved Spacetimes - Lecture 5

Ugo Moschella University of Insubria

October 07, 2013

PIRSA:13100011

Title	Date	Collection	Type	Info
From Supersolidity to Giant Plasticity: Defects in Quantum Crystals	2013‑10‑09	Colloquium	Scientific Series	View details
13/14 PSI - Statistical Mechanics - Lecture 3	2013‑10‑09	13/14 PSI - Statistical Mechanics	Course	View details
Topics in QFT on Flat and Curved Spacetimes - Lecture 6	2013‑10‑09	Topics in QFT on Flat and Curved Spacetimes	Course	View details
General Relativity for Cosmology - Lecture 4	2013‑10‑08	General Relativity for Cosmology - 2013	Course	View details
General Relativity for Cosmology - Lecture 3	2013‑10‑08	General Relativity for Cosmology - 2013	Course	View details
13/14 PSI - Quantum Field Theory I - Lecture 2	2013‑10‑08	13/14 PSI - Quantum Field Theory I	Course	View details
A Nearly Gaussian Hubble-patch in a non-Gaussian Universe	2013‑10‑08	Cosmology and Gravitation	Scientific Series	View details
13/14 PSI - Statistical Mechanics - Lecture 2	2013‑10‑08	13/14 PSI - Statistical Mechanics	Course	View details
Geometry and Topology in the Fractional Quantum Hall Effect	2013‑10‑07	Quantum Matter	Scientific Series	View details
13/14 PSI - Quantum Field Theory I - Lecture 1	2013‑10‑07	13/14 PSI - Quantum Field Theory I	Course	View details
13/14 PSI - Statistical Mechanics - Lecture 1	2013‑10‑07	13/14 PSI - Statistical Mechanics	Course	View details
Topics in QFT on Flat and Curved Spacetimes - Lecture 5	2013‑10‑07	Topics in QFT on Flat and Curved Spacetimes	Course	View details

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