Talks

10369 - 10380 of 16447 Results

Curiosity: How Science Became Interested in Everything

Philip Ball
The Lancet Group

December 05, 2012

PIRSA:12120004
Local topological order inhibits thermal stability in 2D

December 05, 2012

PIRSA:12120010

Quantum Information
The Spectrum of Strings on Warped AdS3

Wei Song
Harvard University

December 05, 2012

PIRSA:12120027

Quantum Fields and Strings
If no information gain implies no disturbance, then any discrete physical theory is classical

Corsin Pfister

December 04, 2012

PIRSA:12120016

Quantum Foundations
Moduli Stabilization and Holographic RG

December 04, 2012

PIRSA:12120002

Quantum Fields and Strings
New electroweak states in plain sight

Patrick Meade
Stony Brook University - C. N. Yang Institute for Theoretical Physics

December 04, 2012

PIRSA:12120017

Particle Physics
Amplitude mode of the d-density wave state and its relevance to high-Tc cuprates

Ipsita Mandal
Shiv Nadar University

November 30, 2012

PIRSA:12110089

Condensed Matter
Statistical Mechanics - Lecture 15

John Berlinsky
McMaster University

November 30, 2012

PIRSA:12110037
Beyond the Search for Majorana

Yi-Zhuang You
University of California, San Diego

November 30, 2012

PIRSA:12110088

Condensed Matter
Quantum Field Theory 2 - Lecture 15

Francois David
CEA Saclay

November 30, 2012

PIRSA:12110018

Quantum Fields and Strings
Universal driven dynamics near phase transitions : Kibble-Zurek ramps with and without an order parameter

Anushya Chandran
Perimeter Institute for Theoretical Physics

November 29, 2012

PIRSA:12110095

Condensed Matter
Fractional quantum Hall effect and tunable interactions

Zlatko Papic
University of Leeds

November 29, 2012

PIRSA:12110081

Condensed Matter

Curiosity: How Science Became Interested in Everything

Philip Ball
The Lancet Group

December 05, 2012

PIRSA:12120004
Local topological order inhibits thermal stability in 2D

December 05, 2012

PIRSA:12120010

Quantum Information

We study the robustness of quantum information stored in the degenerate ground space of a local, frustration-free Hamiltonian with commuting terms on a 2D spin lattice. On one hand, a macroscopic energy barrier separating the distinct ground states under local transformations would protect the information from thermal fluctuations. On the other hand, local topological order would shield the ground space from static perturbations. Here we demonstrate that local topological order implies a constant energy barrier, thus inhibiting thermal stability. Joint work with David Poulin. arXiv:1209.5750
The Spectrum of Strings on Warped AdS3

Wei Song
Harvard University

December 05, 2012

PIRSA:12120027

Quantum Fields and Strings

Warped AdS3 has isometry SL(2,R) x U(1). It is closed related to Kerr/CFT, non local dipole theories and AdS/CMT. In this talk I will derive the spectrum of string theory on Warped AdS3. This is possible because the worldsheet theory can be mapped to the worldsheet on AdS3 by a nonlocal field redefinition.
If no information gain implies no disturbance, then any discrete physical theory is classical

Corsin Pfister

December 04, 2012

PIRSA:12120016

Quantum Foundations

(based on http://arxiv.org/abs/1210.0194) It has been suggested that nature could be discrete in the sense that the underlying state space of a physical system has only a finite number of pure states. For example, the Bloch ball of a single qubit could be discretized into small patches and only appear round to us due to experimental limitations. Here, we present a strong physical argument for the quantum theoretical property that every state space (even the smallest possible one, the qubit) has infinitely many pure states. We propose a simple physical postulate which dictates that in fact the only possible discrete theory is classical mechanics. More specifically, we postulate that no information gain implies no disturbance, or read in the contrapositive, that disturbance leads to some form of information gain. In a theory like quantum mechanics where we already know that the converse holds, i.e. information gain does imply disturbance, this can be understood as postulating an equivalence between disturbance and information gain. What is more, we show that non-classical discrete theories are still ruled out even if we relax the postulate to hold only approximately in the sense that no information gain only causes a small amount of disturbance. Finally, our postulate also rules out popular generalizations such as the PR-box that allows non-local correlations beyond the limits of quantum theory.
Moduli Stabilization and Holographic RG

December 04, 2012

PIRSA:12120002

Quantum Fields and Strings

In this talk, I will relate moduli stabilization in AdS or de Sitter space to basic properties of the Wilsonian action in the holographic dual theory living on dS (of one lower dimension): the single-trace terms in the action have vanishing beta functions, and higher-trace couplings are determined purely from lower-trace ones (a property we refer to as the iterative structure of RG). In the dS case, this encodes the maximal symmetry of the bulk spacetime in a quantity which is accessible within a single observer's patch.
New electroweak states in plain sight

Patrick Meade
Stony Brook University - C. N. Yang Institute for Theoretical Physics

December 04, 2012

PIRSA:12120017

Particle Physics

The LHC has made remarkable progress in exploring the SM at new energies and demonstrating remarkable agreement with theoretical predictions. In this talk I will discuss one area where the SM does not fit as well as expected, and what could be hints of new physics showing up in the electroweak sector.
Amplitude mode of the d-density wave state and its relevance to high-Tc cuprates

Ipsita Mandal
Shiv Nadar University

November 30, 2012

PIRSA:12110089

Condensed Matter

We study the spectrum of the amplitude mode, the analog of the Higgs mode in high energy physics, for the d-density wave (DDW) state proposed to describe the anomalous phenomenology of the pseudogap phase of the high Tc cuprates. Even though the state breaks translational symmetry by a lattice spacing and is described by a particle-hole singlet order parameter at the wave vector q = Q = (pi, pi), remarkably, we find that the amplitude mode spectrum can have peaks at both q = (0, 0) and q = Q = (pi , pi). In general, the spectra is non-universal, and, depending on the microscopic parameters, can have one or two peaks in the Brillouin zone, signifying confluence of two kinds of magnetic excitations. In light of the recent unexpected observations of multiple magnetic excitations in the pseudogap phase our theory sheds important light on how multiple inelastic neutron peaks at different wave vectors can arise even with an order parameter that condenses at Q = (pi, pi). [Reference: arXiv:1207.6834]
Statistical Mechanics - Lecture 15

John Berlinsky
McMaster University

November 30, 2012

PIRSA:12110037
Beyond the Search for Majorana

Yi-Zhuang You
University of California, San Diego

November 30, 2012

PIRSA:12110088

Condensed Matter

The search for Majorana zero-modes in condensed matter system has attract increasing research interests recently. Looking for Majorna zero-mode is actually looking for topologically protected ground state degeneracy. The topological degeneracies on closed manifolds have been used to discover/define topological order in many-body systems, which contain excitations with fractional statistics. In this talk, I will present our recent work on new types of topological degeneracy induced by condensing anyons along a line in 2D topological ordered states. Such topological degeneracy can be viewed as carried by each end of the line-defect, which is a generalization of Majorana zero-modes. The ends of line-defects carry projective non-Abelian statistics even though they are produced by condensation of Abelian anyons, and braiding them allow us to perform fault tolerant quantum computations.
Quantum Field Theory 2 - Lecture 15

Francois David
CEA Saclay

November 30, 2012

PIRSA:12110018

Quantum Fields and Strings
Universal driven dynamics near phase transitions : Kibble-Zurek ramps with and without an order parameter

Anushya Chandran
Perimeter Institute for Theoretical Physics

November 29, 2012

PIRSA:12110095

Condensed Matter

Near a critical point, the equilibrium relaxation time of a system diverges and any change of control parameters leads to non-equilibrium behavior. The Kibble-Zurek (KZ) problem is to determine
the evolution of the system when the change is slow. In this talk, I will introduce a non-equilibrium scaling limit in which these evolutions are universal and define a KZ universality classification with exponents and scaling functions. I will illustrate the physics accessible in this
scaling limit in simple classical and quantum model theories with symmetry-breaking transitions.

I will then turn to the KZ problem near quantum phase transitions without a local order parameter.
First, I will introduce the necessary background through the example of the Ising gauge theory/generalized toric code. Using duality and the scaling theory developed in the first part of the talk, I will then argue that the late time dynamics exhibits a slow coarsening of the string-net
that is condensed in the starting topologically ordered state. I will also discuss a time dependent amplification of the energy splitting between topologically degenerate states on closed manifolds and the dangerous irrelevance of gapped modes. Finally, I will extend these ideas to the non-abelian SU(2)_k ordered phases of the relevant Levin-Wen models.
Fractional quantum Hall effect and tunable interactions

Zlatko Papic
University of Leeds

November 29, 2012

PIRSA:12110081

Condensed Matter

In this talk I will review some existing experimental methods, as well as a few recent theoretical proposals, to tune the interactions in a number of low-dimensional systems exhibiting the fractional quantum Hall effect (FQHE). The materials in question include GaAs wide quantum wells and multilayer graphene, where the tunability of the electron-electron interactions can be achieved via modifying the band structure, dielectric environment of the sample, by tilting the magnetic field or varying the mass tensor, and by mixing of electronic subbands and Landau levels. Because the interesting topological (and in particular, non-Abelian) states arise solely due to strong interactions, the ability to tune them is essential for ``designing" more robust FQHE states. Furthermore, I will argue that some of these mechanisms can also be used to probe the subtle aspects of FQHE physics, such as the breaking of particle-hole symmetry between the Moore-Read Pfaffian and anti-Pfaffian states, and the transition between FQHE fluids and broken-symmetry states due to the fluctuation of the intrinsic geometric degree of freedom.

Title	Date	Collection	Type	Info
Curiosity: How Science Became Interested in Everything	2012‑12‑05	Public Lecture Series	Public Lectures	View details
Local topological order inhibits thermal stability in 2D	2012‑12‑05	Quantum Information	Scientific Series	View details
The Spectrum of Strings on Warped AdS3	2012‑12‑05	Quantum Fields and Strings	Scientific Series	View details
If no information gain implies no disturbance, then any discrete physical theory is classical	2012‑12‑04	Quantum Foundations	Scientific Series	View details
Moduli Stabilization and Holographic RG	2012‑12‑04	Quantum Fields and Strings	Scientific Series	View details
New electroweak states in plain sight	2012‑12‑04	Particle Physics	Scientific Series	View details
Amplitude mode of the d-density wave state and its relevance to high-Tc cuprates	2012‑11‑30	Quantum Matter	Scientific Series	View details
Statistical Mechanics - Lecture 15	2012‑11‑30	12/13 PSI - Statistical Mechanics	Course	View details
Beyond the Search for Majorana	2012‑11‑30	Quantum Matter	Scientific Series	View details
Quantum Field Theory 2 - Lecture 15	2012‑11‑30	12/13 PSI - Quantum Field Theory 2	Course	View details
Universal driven dynamics near phase transitions : Kibble-Zurek ramps with and without an order parameter	2012‑11‑29	Quantum Matter	Scientific Series	View details
Fractional quantum Hall effect and tunable interactions	2012‑11‑29	Quantum Matter	Scientific Series	View details

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