Talks

12385 - 12396 of 20120 Results

The World is Discrete

Olaf Dreyer Freelance Consultant

September 19, 2013

PIRSA:13090073

General Relativity & Quantum Cosmology
13/14 PSI - Quantum Theory - Lecture 9

Joseph Emerson Institute for Quantum Computing (IQC)

September 19, 2013

PIRSA:13090040
13/14 PSI - Relativity - Lecture 9

Neil Turok University of Edinburgh

September 19, 2013

PIRSA:13090021
Short Gamma-Ray Bursts and the Electromagnetic Counterparts of Gravitational Wave Sources

Edo Berger Harvard University

September 18, 2013

PIRSA:13090050
13/14 PSI - Quantum Theory - Lecture 8

Joseph Emerson Institute for Quantum Computing (IQC)

September 18, 2013

PIRSA:13090039
13/14 PSI - Relativity - Lecture 8

Neil Turok University of Edinburgh

September 18, 2013

PIRSA:13090020
Self-organized topological state with Majorana fermions

Marcel Franz University of British Columbia

September 17, 2013

PIRSA:13090071

Condensed Matter
Coalgebras, Models and Logics for Quantum Systems

September 17, 2013

PIRSA:13090072

Quantum Physics
Orbifolds and topological defects

Daniel Plencner Ludwig-Maximilians-Universität München (LMU)

September 17, 2013

PIRSA:13090061

High Energy Physics
ΛCDM Large Scale Triumphs and Small Scale Challenges

Joel Primack University of California, Santa Cruz

September 17, 2013

PIRSA:13090066

Astrophysics
13/14 PSI - Quantum Theory - Lecture 7

Joseph Emerson Institute for Quantum Computing (IQC)

September 17, 2013

PIRSA:13090038
13/14 PSI - Relativity - Lecture 7

Neil Turok University of Edinburgh

September 17, 2013

PIRSA:13090019

The World is Discrete

Olaf Dreyer Freelance Consultant

September 19, 2013

PIRSA:13090073

General Relativity & Quantum Cosmology

We argue that the scale-free spectrum that is observed in the cosmic microwave background is the result of a phase transition in the early universe. The observed tilt of the spectrum, which has been measured to be 0.04, is shown to be equal to the anomalous scaling dimension of the correlation function. The phase transition replaces inflation as the mechanism that produces this spectrum. The tilt further indicates that there is a fundamental small length scale in nature that we have not yet observed in any other way.
13/14 PSI - Quantum Theory - Lecture 9

Joseph Emerson Institute for Quantum Computing (IQC)

September 19, 2013

PIRSA:13090040
13/14 PSI - Relativity - Lecture 9

Neil Turok University of Edinburgh

September 19, 2013

PIRSA:13090021
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.
13/14 PSI - Quantum Theory - Lecture 8

Joseph Emerson Institute for Quantum Computing (IQC)

September 18, 2013

PIRSA:13090039
13/14 PSI - Relativity - Lecture 8

Neil Turok University of Edinburgh

September 18, 2013

PIRSA:13090020
Self-organized topological state with Majorana fermions

Marcel Franz University of British Columbia

September 17, 2013

PIRSA:13090071

Condensed Matter

Topological phases, quite generally, are difficult to come by. They either occur under rather extreme conditions (e.g. the quantum Hall liquids, which require high sample purity, strong magnetic fields and low temperatures) or demand fine tuning of system parameters, as in the majority of known topological insulators. Many perfectly sensible topological phases, such as the Weyl semimetals and topological superconductors, remain experimentally undiscovered. In this talk I will introduce a system in which a key dynamical parameter adjusts itself in response to the changing external conditions so that the ground state naturally favors the topological phase. The system consists of a quantum wire formed of individual magnetic atoms placed on the surface of an ordinary s-wave superconductor. It realizes the Kitaev paradigm of topological superconductivity when the wavevector characterizing the emergent spin helix dynamically self-tunes to support the topological phase.
Coalgebras, Models and Logics for Quantum Systems

September 17, 2013

PIRSA:13090072

Quantum Physics

Coalgebras are a flexible tool commonly used in computer science to model abstract devices and systems. Coalgebraic models also come with a natural notion of logics for the systems being modelled. In this talk we will introduce coalgebras and aim to illustrate their usefulness for modelling physical systems. Extending earlier work of Abramsky, we will show how a weakening of the usual morphisms for coalgebras provides the flexibility to model quantum systems in an easy to motivate manner. We will then investigate how a natural extension to the usual notion of coalgebraic logic can be used to produce logics for reasoning about quantum systems and protocols. No prior knowledge of coalgebras will be assumed for this talk, and the emphasis throughout will be on examples rather than technical details.
Orbifolds and topological defects

Daniel Plencner Ludwig-Maximilians-Universität München (LMU)

September 17, 2013

PIRSA:13090061

High Energy Physics

Orbifolding a 2-dimensional quantum field theory by a symmetry group admits an elegant description in terms of defect lines and their junction fields. This perspective offers a natural generalization of the concept of an orbifold, in which the role of the symmetry group is replaced by a defect with the structure of a (symmetric) separable Frobenius algebra. In this talk I will focus on the case of Landau-Ginzburg models, in which defects are described by matrix factorizations. After introducing the generalized twisted sectors and discussing topological bulk and boundary correlators in these sectors, I will present a simple proof of the Cardy condition and discuss some further consistency checks on the generalized orbifold theory. This talk is based on arXiv:1307.3141 with Ilka Brunner and Nils Carqueville.
ΛCDM Large Scale Triumphs and Small Scale Challenges

Joel Primack University of California, Santa Cruz

September 17, 2013

PIRSA:13090066

Astrophysics

ΛCDM has become the standard cosmological model because its predictions agree so well with observations of the cosmic microwave background and the large-scale structure of the universe. However ΛCDM has faced challenges on smaller scales. Some of these challenges, including the “angular momentum catastrophe" and the absence of density cusps in the centers of small galaxies, may be overcome with improvements in simulation resolution and feedback. Recent simulations appear to form realistic galaxies in agreement with observed scaling relations. Although dark matter halos start small and grow by accretion, the existence of a star-forming band of halo masses naturally explains why the most massive galaxies have the oldest stars, a phenomenon known as galactic “downsizing." The discovery of many faint galaxies in the Local Group is consistent with the large number of subhalos in ΛCDM simulations. There is increasing evidence for such substructure in galaxy dark matter halos from gaps in cold stellar streams in the Milky Way and Andromeda and from gravitational lensing flux anomalies, with the prospect of rapidly increasing data on that from ALMA. The “too big to fail" (TBTF) problem is the latest apparent challenge to ΛCDM. It arose from analysis of the Aquarius and Via Lactea very-high-resolution ΛCDM simulations of Milky-Way-mass dark matter halos. Each simulated halo has ∼10 subhalos so massive and dense that they would appear to be too big to fail to form lots of stars. The TBTF problem is that none of the observed dwarf satellite galaxies of the Milky Way or Andromeda have stars moving as fast as would be expected in these densest subhalos. This may indicate the need for a more complex theory of dark matter – but several recent papers have shown that subhalos in pure dark matter simulations like Aquarius or Via Lactea are significantly modified when baryonic effects are included, so as to solve the TBTF problem. Higher resolution simulations are needed to verify this.
13/14 PSI - Quantum Theory - Lecture 7

Joseph Emerson Institute for Quantum Computing (IQC)

September 17, 2013

PIRSA:13090038
13/14 PSI - Relativity - Lecture 7

Neil Turok University of Edinburgh

September 17, 2013

PIRSA:13090019

Title	Date	Collection	Type	Info
The World is Discrete	2013‑09‑19	Quantum Gravity	Scientific Series	View details
13/14 PSI - Quantum Theory - Lecture 9	2013‑09‑19	13/14 PSI - Quantum Theory	Course	View details
13/14 PSI - Relativity - Lecture 9	2013‑09‑19	13/14 PSI - Relativity	Course	View details
Short Gamma-Ray Bursts and the Electromagnetic Counterparts of Gravitational Wave Sources	2013‑09‑18	Colloquium	Scientific Series	View details
13/14 PSI - Quantum Theory - Lecture 8	2013‑09‑18	13/14 PSI - Quantum Theory	Course	View details
13/14 PSI - Relativity - Lecture 8	2013‑09‑18	13/14 PSI - Relativity	Course	View details
Self-organized topological state with Majorana fermions	2013‑09‑17	Quantum Matter	Scientific Series	View details
Coalgebras, Models and Logics for Quantum Systems	2013‑09‑17	Quantum Foundations	Scientific Series	View details
Orbifolds and topological defects	2013‑09‑17	Quantum Fields and Strings	Scientific Series	View details
ΛCDM Large Scale Triumphs and Small Scale Challenges	2013‑09‑17	Cosmology and Gravitation	Scientific Series	View details
13/14 PSI - Quantum Theory - Lecture 7	2013‑09‑17	13/14 PSI - Quantum Theory	Course	View details
13/14 PSI - Relativity - Lecture 7	2013‑09‑17	13/14 PSI - Relativity	Course	View details

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Format results

The World is Discrete

13/14 PSI - Quantum Theory - Lecture 9

13/14 PSI - Relativity - Lecture 9

Short Gamma-Ray Bursts and the Electromagnetic Counterparts of Gravitational Wave Sources

13/14 PSI - Quantum Theory - Lecture 8

13/14 PSI - Relativity - Lecture 8

Self-organized topological state with Majorana fermions

Coalgebras, Models and Logics for Quantum Systems

Orbifolds and topological defects

ΛCDM Large Scale Triumphs and Small Scale Challenges

13/14 PSI - Quantum Theory - Lecture 7

13/14 PSI - Relativity - Lecture 7

The World is Discrete

13/14 PSI - Quantum Theory - Lecture 9

13/14 PSI - Relativity - Lecture 9

Short Gamma-Ray Bursts and the Electromagnetic Counterparts of Gravitational Wave Sources

13/14 PSI - Quantum Theory - Lecture 8

13/14 PSI - Relativity - Lecture 8

Self-organized topological state with Majorana fermions

Coalgebras, Models and Logics for Quantum Systems

Orbifolds and topological defects

ΛCDM Large Scale Triumphs and Small Scale Challenges

13/14 PSI - Quantum Theory - Lecture 7

13/14 PSI - Relativity - Lecture 7