Scientific Series

Displaying 3121 - 3132 of 5012

Inflation After Planck
March 18, 2014

PIRSA:14030116
Cosmology
Seeing is Believing: Direct Observation of a General Quantum State

Jeff Lundeen
University of Ottawa
March 17, 2014

PIRSA:14030110
Quantum Foundations
Are superselection rules fundamental?

Robert Spekkens
Perimeter Institute for Theoretical Physics
March 14, 2014

PIRSA:14030114
Condensed Matter
Asymptotic Symmetries of Gauge and Gravity Theories in Minkowski Space

Andrew Strominger
Harvard University
March 13, 2014

PIRSA:14030087
Strong Gravity
Maximal Privacy Without Coherence

Debbie Leung
Institute for Quantum Computing (IQC)
March 12, 2014

PIRSA:14030105
Quantum Information
Black Holes- the Harmonic Oscillators of the 21st Century

Andrew Strominger
Harvard University
March 12, 2014

PIRSA:14030104
Quantum Fields and Strings
DMRG Analysis of Mobile Impurities and Orbital-selective Mott Phases

Julian (Jose) Rincon
Universidad de los Andes
March 12, 2014

PIRSA:14030117
Condensed Matter
Exact holographic mapping and emergent space-time geometry

Xiaoliang Qi
Stanford University
March 11, 2014

PIRSA:14030107
Condensed Matter
Line Defects and Tropicalization

Clay Cordova
University of Chicago
March 11, 2014

PIRSA:14030106
Quantum Fields and Strings
SDSS-III BOSS and Beyond: fundamental physics with galaxy redshift surveys

Beth Reid
Lawrence Berkeley National Laboratory
March 11, 2014

PIRSA:14030096
Cosmology
A one-dimensional action for simplicial gravity in three dimensions

Wolfgang Wieland
University of Erlangen-Nuremberg
March 06, 2014

PIRSA:14030088
Quantum Gravity
Sequestering Lorentz violation in the Lifshitz sector

Maxim Pospelov
University of Minnesota
March 06, 2014

PIRSA:14030092
Strong Gravity

Inflation After Planck
March 18, 2014

PIRSA:14030116
Cosmology
The Planck satellite measurement of the cosmic microwave background has provided spectacular confirmation of the predictions of inflationary cosmology, putting inflation on a firm footing as the leading theory of the very early universe. I will discuss the implications of Planck for the simplest canonical single-field inflation models, which are favored by the data. Then I will discuss the most general question: How strong is the case that inflation is the "right" theory of the early universe?
Seeing is Believing: Direct Observation of a General Quantum State

Jeff Lundeen
University of Ottawa
March 17, 2014

PIRSA:14030110
Quantum Foundations
Central to quantum theory, the wavefunction is a complex distribution associated with a quantum system. Despite its fundamental role, it is typically introduced as an abstract element of the theory with no explicit definition. Rather, physicists come to a working understanding of it through its use to calculate measurement outcome probabilities through the Born Rule. Tomographic methods can reconstruct the wavefunction from measured probabilities. In contrast, I present a method to directly measure the wavefunction so that its real and imaginary components appear straight on our measurement apparatus. I will also present new work extending this concept to mixed quantum states. This extension directly measures a little-known proposal by Dirac for a classical analog to a quantum operator. Furthermore, it reveals that our direct measurement is a rigorous example of a quasi-probability phase-space (i.e. x,p) distribution that is closely related to the Q, P, and Wigner functions. Our direct measurement method gives the quantum state a plain and general meaning in terms of a specific set of simple operations in the lab.
Are superselection rules fundamental?

Robert Spekkens
Perimeter Institute for Theoretical Physics
March 14, 2014

PIRSA:14030114
Condensed Matter
Superselection rules in quantum theory assert the impossibility of preparing coherent superpositions of certain conserved quantities. For instance, it is commonly presumed that there is a superselection rule for charge and for baryon number, as well as a "univalence superselection rule" forbidding a coherent superposition of a fermion and a boson. I will show how many superselection rules can be effectively lifted using a reference frame for the variable that is conjugate to the conserved quantity. I will also discuss subtleties related to the univalence superselection rule.
Asymptotic Symmetries of Gauge and Gravity Theories in Minkowski Space

Andrew Strominger
Harvard University
March 13, 2014

PIRSA:14030087
Strong Gravity
We argue that the infinite-dimensional BMS symmetry discovered by Bondi et. al in the 60s provides an exact symmetry of the quantum gravity S-matrix. The Ward identity of this symmetry is shown to be precisely Weinberg's soft graviton theorem, also discovered in the 60s. A parallel infinite-dimensional symmetry is found to be generated in nonabelian gauge theories by gauge transformations which go to an angle-dependent finite constant at null infinity. The Ward identity of this symmetry is shown to be the soft gluon theorem.
Maximal Privacy Without Coherence

Debbie Leung
Institute for Quantum Computing (IQC)
March 12, 2014

PIRSA:14030105
Quantum Information
Privacy and coherence have long been considered closely related properties of a quantum state. Indeed, a coherently transmitted quantum state is inherently private. Surprisingly, coherent quantum communication is not always required for privacy: there are quantum channels that are too noisy to transmit quantum information but it can send private classical information. Here, we ask how different the private classical and the quantum capacities can be. We present a class of channels N_d with input dimension d^2, quantum capacity Q(N_d) <= 1, and private classical capacity P(N_d) = log d. These channels asymptotically saturate an interesting inequality P(N) <= (log d_A + Q(N))/2 for any channel N with input dimension d_A, and capture the essence of privacy stripped of the confounding influence of coherence.
Black Holes- the Harmonic Oscillators of the 21st Century

Andrew Strominger
Harvard University
March 12, 2014

PIRSA:14030104
Quantum Fields and Strings
In the twentieth century, many problems across all of physics were solved by perturbative methods which reduced them to harmonic oscillators. Black holes are poised to play a similar role for the problems of twenty-first century physics. They are at once the simplest and most complex objects in the physical universe. They are maximally complex in that the number of possible microstates, or entropy, of a black hole is believed to saturate a universal bound. They are maximally simple in that, according to Einstein's theory, they are featureless holes in space characterized only by their mass, charge and angular momentum. This dual relation between simplicity and complexity, as expressed in black holes, has recently been successfully applied to problems in a disparate variety of physical systems. I will give an introduction to the subject intended for a general audience.
DMRG Analysis of Mobile Impurities and Orbital-selective Mott Phases

Julian (Jose) Rincon
Universidad de los Andes
March 12, 2014

PIRSA:14030117
Condensed Matter
Exact holographic mapping and emergent space-time geometry

Xiaoliang Qi
Stanford University
March 11, 2014

PIRSA:14030107
Condensed Matter
Holographic duality is a duality between quantum many-body systems (boundary) and gravity systems with one additional spatial dimension (bulk). In this talk, I will describe a new approach to holographic duality for lattice systems, called the exact holographic mapping. The key idea of this approach can be summarized by two points: 1) The bulk theory is nothing but the boundary theory viewed in a different basis. 2) Space-time geometry is determined by the structure of correlations and quantum entanglement in a quantum state. For free fermion boundary theories, I will show how different bulk geometries including AdS space, black holes and worm-holes emerge. I will also discuss the generalization of this approach in more generic interacting systems.
Line Defects and Tropicalization

Clay Cordova
University of Chicago
March 11, 2014

PIRSA:14030106
Quantum Fields and Strings
I will review BPS line defects in 4d N=2 field theories and describe a technique for calculating their spectra using quiver quantum mechanics.
SDSS-III BOSS and Beyond: fundamental physics with galaxy redshift surveys

Beth Reid
Lawrence Berkeley National Laboratory
March 11, 2014

PIRSA:14030096
Cosmology
The SDSS-III Baryon Oscillation Spectroscopic Survey, now nearly complete, is measuring the three-dimensional cosmic structure with 1.35 million new redshifts. Galaxy clustering measurements provide constraints on the cosmic expansion history through the baryon acoustic oscillation feature and the Alcock-Paczynski effect. In addition, the imprint of galaxy peculiar velocities on the observed galaxy clustering, "redshift-space distortions", provides a measurement of the growth rate of matter perturbations. Taken together, these measurements provide excellent constraints on dark energy and test the relation between expansion history and growth of perturbations expected in General Relativity. I will summarize results from BOSS's recent DR11 results and highlight what we may learn about fundamental physics (especially neutrinos) from the upcoming Dark Energy Spectroscopic Instrument (DESI).
A one-dimensional action for simplicial gravity in three dimensions

Wolfgang Wieland
University of Erlangen-Nuremberg
March 06, 2014

PIRSA:14030088
Quantum Gravity
Loop quantum gravity has a spinorial representation. Spinors simplify the symplectic structure of the theory, but can they also teach us something about the dynamics? We study this question in three dimensions, and derive the Ponzano–-Regge model from a spinorial action. Our construction starts from the first-order Palatini formalism, and gives the discretised action in the spinorial representation. A one-dimensional refinement limit brings us back to a continuum theory. The three-dimensional action turns into a line integral over the edges of the discretisation. We compute the gauge-fixed path integral for a generic simplicial discretisation. The resulting amplitudes reproduce the Ponzano–-Regge model.
Sequestering Lorentz violation in the Lifshitz sector

Maxim Pospelov
University of Minnesota
March 06, 2014

PIRSA:14030092
Strong Gravity
Horava's proposal to use Lifshitz propagators for gravitons above certain energy scales may provide a viable theory of quantum gravity without further need of UV completion. In my talk, I will address the question of whether the complete lack of Lorentz invariance above a certain energy scale is a big problem for any realistic construction. I will argue that it is not, provided that the onset of Lifshitz scaling for gravitons occurs at momentum scale much lower than the Planck mass. I will also discuss consequences of combining Lifshitz gravity and supersymmetric matter sector.

Title	Speaker(s)	Date	Talk Type	Info link
Inflation After Planck		2014-03-18	Scientific Series	View details
Seeing is Believing: Direct Observation of a General Quantum State	Jeff Lundeen	2014-03-17	Scientific Series	View details
Are superselection rules fundamental?	Robert Spekkens	2014-03-14	Scientific Series	View details
Asymptotic Symmetries of Gauge and Gravity Theories in Minkowski Space	Andrew Strominger	2014-03-13	Scientific Series	View details
Maximal Privacy Without Coherence	Debbie Leung	2014-03-12	Scientific Series	View details
Black Holes- the Harmonic Oscillators of the 21st Century	Andrew Strominger	2014-03-12	Scientific Series	View details
DMRG Analysis of Mobile Impurities and Orbital-selective Mott Phases	Julian (Jose) Rincon	2014-03-12	Scientific Series	View details
Exact holographic mapping and emergent space-time geometry	Xiaoliang Qi	2014-03-11	Scientific Series	View details
Line Defects and Tropicalization	Clay Cordova	2014-03-11	Scientific Series	View details
SDSS-III BOSS and Beyond: fundamental physics with galaxy redshift surveys	Beth Reid	2014-03-11	Scientific Series	View details
A one-dimensional action for simplicial gravity in three dimensions	Wolfgang Wieland	2014-03-06	Scientific Series	View details
Sequestering Lorentz violation in the Lifshitz sector	Maxim Pospelov	2014-03-06	Scientific Series	View details

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