Talks

10753 - 10764 of 16754 Results

Penrose inequalities and the stability of non-uniform black strings

Pau Figueras Queen Mary University of London

November 01, 2012

PIRSA:12110039
What is a Wavefunction?

Wayne Myrvold Western University

November 01, 2012

PIRSA:12110060
An Informal Discussion About Topological Gauge Theory, part 2

Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics

October 30, 2012

PIRSA:12100132
Fault tolerance of "bad" quantum low-density parity check codes

Alexey Kovalev University of California, Riverside

October 29, 2012

PIRSA:12100130
Synthetic non-Abelian anyons in fractional Chern insulators and beyond

Xiaoliang Qi Stanford University

October 26, 2012

PIRSA:12100051

Condensed Matter
Condensed Matter - Lecture 14

Assa Auerbach Technion – Israel Institute of Technology

October 26, 2012

PIRSA:12100039

Condensed Matter
Quantum Field Theory - Lecture 14B

Konstantin Zarembo Nordic Institute for Theoretical Physics

October 26, 2012

PIRSA:12100075

Quantum Fields and Strings
Quantum Field Theory - Lecture 14A

Konstantin Zarembo Nordic Institute for Theoretical Physics

October 26, 2012

PIRSA:12100021

Quantum Fields and Strings
Effective field theory framework in QG

Xavier Calmet University of Sussex

Roberto Percacci SISSA International School for Advanced Studies

Astrid Eichhorn Universität Heidelberg

Martin Reuter Johannes Gutenberg University Mainz

October 25, 2012

PIRSA:12100121

Quantum Gravity
Experimental tests of CPT symmetry

Antonio Di Domenico Sapienza University of Rome

October 25, 2012

PIRSA:12100120
Kicking Chameleons: Early Universe Challenges for Chameleon Gravity

Adrienne Erickcek University of North Carolina at Chapel Hill

October 25, 2012

PIRSA:12100125

Cosmology
Quantum Field Theory - Lecture 13B

Konstantin Zarembo Nordic Institute for Theoretical Physics

October 25, 2012

PIRSA:12100074

Quantum Fields and Strings

Penrose inequalities and the stability of non-uniform black strings

Pau Figueras Queen Mary University of London

November 01, 2012

PIRSA:12110039

In this talk I will first review static black holes in Kaluza-Klein theory. It is well-known that within this theory there exist black strings which are non-uniform along the Kaluza-Klein circle. Using numerical methods, I will explain how to construct (for the first time) non-uniform black strings in D>10, where D is the total number of spacetime dimensions. The stability of such black objects has not been discussed before, and in the last part of the talk I will explain how one can study the stability of non-uniform black strings using Penrose inequalities. This will lead to a new conjecture for the phase diagram of static Kaluza-Klein black holes.
What is a Wavefunction?

Wayne Myrvold Western University

November 01, 2012

PIRSA:12110060

The fact that the quantum wavefunction of a many-particle system is a function on a high-dimensional configuration space, rather than on spacetime, has led some to suggest that any realist understanding of quantum mechanics must regard configuration space as more fundamental than spacetime. Worse, it seems that a wavefunction monist ontology cannot help itself to talk of "configuration space" at all, without particles for the configurations to be configurations of. The wavefunction, it might seem, threatens to become a function defined on a high-dimensional space whose relation to spacetime is obscure. I will argue that such worries are misplaced.
An Informal Discussion About Topological Gauge Theory, part 2

Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics

October 30, 2012

PIRSA:12100132

Reference:
Topological gauge theories and group cohomology
Robbert Dijkgraaf and Edward Witten
http://projecteuclid.org/DPubS?service=UI&version=1.0&verb=Display&handle=euclid.cmp/1104180750

Braiding statistics approach to symmetry-protected topological phases
Michael Levin, Zheng-Cheng Gu
http://arxiv.org/abs/1202.3120
Fault tolerance of "bad" quantum low-density parity check codes

Alexey Kovalev University of California, Riverside

October 29, 2012

PIRSA:12100130

In my talk, I will discuss various families of quantum low-density parity check (LDPC) codes and their fault tolerance. Such codes yield finite code rates and at the same time simplify error correction and encoding due to low-weight stabilizer generators. As an example, a large family of hypergraph-product codes is considered. Of particular interest are families of quantum LDPC codes with finite rate and distance scaling as square root of blocklength since this represents the best known exponent in distance scaling, even for codes of dimensionality 1. In relation to such codes, we show that any family of LDPC codes, quantum or classical, where distance scales as a positive power of the block length, $d \propto n^\alpha$, $\alpha>0$ ($\alpha<1$ for "bad" codes), can correct all errors with certainty if the error rate per qubit is sufficiently small. We specifically analyze the case of LDPC version of the quantum hypergraph-product codes recently suggested by Tillich and Z\'emor. These codes are a finite-rate generalization of the toric codes, and, for sufficiently large quantum computers, offer an advantage over the toric codes.
Synthetic non-Abelian anyons in fractional Chern insulators and beyond

Xiaoliang Qi Stanford University

October 26, 2012

PIRSA:12100051

Condensed Matter

An exciting new prospect in condensed matter physics is the possibility of realizing fractional quantum Hall states in simple lattice models without a large external magnetic field, which are called fractional Chern insulators. A fundamental question is whether qualitatively new states can be realized on the lattice as compared with ordinary fractional quantum Hall states. Here we propose new symmetry-enriched topological states, topological nematic states, which are a dramatic consequence of the interplay between the lattice translational symmetry and topological properties of these fractional Chern insulators. The topological nematic states are realized in a partially filled flat band with a Chern number N, which can be mapped to an N-layer quantum Hall system on a regular lattice. However, in the topological nematic states the lattice dislocations become non-Abelian defects which create "worm holes" connecting the effective layers, and effectively change the topology of the space. Such topology-changing defects, which we name as "genons", can also be defined in other physical systems. We develop methods to compute the projective non-abelian braiding statistics of the genons, and we find the braiding is given by adiabatic modular transformations, or Dehn twists, of the topological state on the effective genus g surface. We find situations where the > genons have quantum dimension 2 and can be used for universal topological quantum computing (TQC), while the host topological state is by itself non-universal for TQC.
Condensed Matter - Lecture 14

Assa Auerbach Technion – Israel Institute of Technology

October 26, 2012

PIRSA:12100039

Condensed Matter
Quantum Field Theory - Lecture 14B

Konstantin Zarembo Nordic Institute for Theoretical Physics

October 26, 2012

PIRSA:12100075

Quantum Fields and Strings
Quantum Field Theory - Lecture 14A

Konstantin Zarembo Nordic Institute for Theoretical Physics

October 26, 2012

PIRSA:12100021

Quantum Fields and Strings
Effective field theory framework in QG

Xavier Calmet University of Sussex

Roberto Percacci SISSA International School for Advanced Studies

Astrid Eichhorn Universität Heidelberg

Martin Reuter Johannes Gutenberg University Mainz

October 25, 2012

PIRSA:12100121

Quantum Gravity

Gravity Induced Grand Unification
Motivated by the lack of evidence for physics beyond the Standard Model in the TeV region, we discussed an alternative path for grand unification. We show that simple grand unification models based on e.g. SU(5) can work successfully even without low scale supersymmetry. In particular quantum gravitational effects could easily modify the unification conditions for the gauge and Yukawa couplings.
_____________________________

Testing the consistency of quantum gravity with low-energy properties of the standard model
Testing quantum gravity is possible by using, e.g. the available data on the properties of the standard model. I will discuss how a parameterisation of quantum gravity fluctuations in terms of metric fluctuations can be used to test the compatibility of quantum gravity with the observed low-energy properties of the standard model, such as the existence of fermions with masses much below the Planck mass.
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The Asymptotic Safety program
The effective average action approach to Quantum Einstein Gravity (QEG) is discussed as a natural framework for exploring the scale dependent Riemannian geometry and multifractal micro-structure of the effective spacetimes predicted by QEG. Their fractal properties are related to the functional RG flow on theory space, and the special role of the running cosmological constant is emphasized. The prospects of an experimental verification will also be discussed.
Experimental tests of CPT symmetry

Antonio Di Domenico Sapienza University of Rome

October 25, 2012

PIRSA:12100120

The three discrete symmetries of Quantum Mechanics, charge conjugation, parity, and time reversal, are all violated, singly or in pairs. CPT is the only combination of these symmetries which appears to be conserved in Nature. Even though this result is in agreement with the well known CPT theorem, that holds for standard quantum field theories, CPT violation in some cases might be expected and justified in the framework of a quantum theory of gravity. Here the last and more refined experimental searches for CPT violation effects will be reported with a special focus on the tests performed on neutral meson systems and the interplay between CPT symmetry and the basic principles of Quantum Mechanics. No deviation from the expectations of CPT symmetry and quantum mechanics is observed, while the precision of the measurements, in some cases, reaches the interesting Planck scale region. Finally, prospects for this kind of experimental studies will be presented.
Kicking Chameleons: Early Universe Challenges for Chameleon Gravity

Adrienne Erickcek University of North Carolina at Chapel Hill

October 25, 2012

PIRSA:12100125

Cosmology

Chameleon gravity is a scalar-tensor theory that mimics general relativity in the Solar System. The scalar degree of freedom is hidden in high-density environments because the effective mass of the chameleon scalar depends on the trace of the stress-energy tensor. In the early Universe, when the trace of the stress-energy tensor is nearly zero, the chameleon is very light and Hubble friction prevents it from reaching its potential minimum. Whenever a particle species becomes non-relativistic, however, the trace of the stress-energy tensor is temporarily nonzero, and the chameleon begins to roll. I will show that these "kicks" to the chameleon field have catastrophic consequences for chameleon gravity. The velocity imparted to the chameleon is sufficiently large that the chameleon's mass changes rapidly as it slides past its potential minimum. This nonadiabatic process shatters the chameleon field by generating extremely high-energy perturbations, casting doubt on chameleon gravity's viability as an alternative to general relativity.
Quantum Field Theory - Lecture 13B

Konstantin Zarembo Nordic Institute for Theoretical Physics

October 25, 2012

PIRSA:12100074

Quantum Fields and Strings

Title	Date	Collection	Type	Info
Penrose inequalities and the stability of non-uniform black strings	2012‑11‑01	Strong Gravity	Scientific Series	View details
What is a Wavefunction?	2012‑11‑01	Quantum Foundations	Scientific Series	View details
An Informal Discussion About Topological Gauge Theory, part 2	2012‑10‑30	Quantum Matter	Other	View details
Fault tolerance of "bad" quantum low-density parity check codes	2012‑10‑29	Perimeter Institute Quantum Discussions	Scientific Series	View details
Synthetic non-Abelian anyons in fractional Chern insulators and beyond	2012‑10‑26	Quantum Matter	Scientific Series	View details
Condensed Matter - Lecture 14	2012‑10‑26	12/13 PSI - Condensed Matter	Course	View details
Quantum Field Theory - Lecture 14B	2012‑10‑26	12/13 PSI - Quantum Field Theory 1	Course	View details
Quantum Field Theory - Lecture 14A	2012‑10‑26	12/13 PSI - Quantum Field Theory 1	Course	View details
Effective field theory framework in QG	2012‑10‑25	Experimental Search for Quantum Gravity 2012	Conference	View details
Experimental tests of CPT symmetry	2012‑10‑25	Experimental Search for Quantum Gravity 2012	Conference	View details
Kicking Chameleons: Early Universe Challenges for Chameleon Gravity	2012‑10‑25	Cosmology and Gravitation	Scientific Series	View details
Quantum Field Theory - Lecture 13B	2012‑10‑25	12/13 PSI - Quantum Field Theory 1	Course	View details

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