Scientific Series

Displaying 3313 - 3324 of 5113

Dimensional reduction in the sky
November 21, 2013

PIRSA:13110059
Quantum Gravity
Charged particle motion in magnetized black holes

Valeri Frolov University of Alberta
November 21, 2013

PIRSA:13110066
Strong Gravity
Quantum Adversary (Upper) Bound

Shelby Kimmel Massachusetts Institute of Technology (MIT)
November 20, 2013

PIRSA:13110090
Quantum Information
Light and matter: towards macroscopic quantum systems

Jacob Taylor Office of Science and Technology Policy
November 20, 2013

PIRSA:13110060
Quantum Information
The Amplitude Mode in Condensed Matter : Higgs Hunting on a Budget

Daniel Arovas University of California, San Diego
November 19, 2013

PIRSA:13110054
Condensed Matter
New Light Species and the CMB - Joint Cosmology/Particle Physics Seminar

Christopher Brust
November 19, 2013

PIRSA:13110051
Particle Physics
Topological States in Strongly-Correlated Materials

Kai Sun University of Michigan–Ann Arbor
November 15, 2013

PIRSA:13110082
Condensed Matter
N-body lensed CMB maps: lensing extraction and characterization

Claudia Antolini SISSA International School for Advanced Studies
November 15, 2013

PIRSA:13110088
Cosmology
Finite regions, spherical entanglement, and quantum gravity

Hal Haggard Bard College
November 14, 2013

PIRSA:13110049
Quantum Gravity
Self-force and Green function in Schwarzschild spacetime via quasinormal modes and branch cut

Marc Casals Universität Leipzig
November 14, 2013

PIRSA:13110067
Strong Gravity
Bulk-boundary correspondence in PEPS

Ignacio Cirac Max Planck Institute for Gravitational Physics - Albert Einstein Institute (AEI)
November 13, 2013

PIRSA:13110058
Quantum Information
Spin and Long-Range Forces: The Unfinished Tale of the Last Massless Particle

Natalia Toro Stanford University
November 13, 2013

PIRSA:13110047
Particle Physics

Dimensional reduction in the sky
November 21, 2013

PIRSA:13110059
Quantum Gravity
In several approaches to quantum-gravity, the spectral dimension of spacetime runs from the standard value of 4 in the infrared (IR) to a smaller value in the ultraviolet (UV). Describing this running in terms of deformed dispersion relations, I show that a striking cosmological implication is that that UV behavior leading to 2 spectral dimensions results in an exactly scale-invariant spectrum of vacuum scalar and tensor fluctuations. I discuss scenarios that break exact scale-invariance and show that the tensor to scalar ratio is fixed by the UV ratio between the speed of gravity and the speed of light. Cosmological perturbations in this framework display a wavelength-dependent speed of light, but by transforming to a suitable "rainbow frame" this feature can be removed, at the expense of modifying gravity. In particular it turns out that the following concepts are closely connected: scale-invariance of vacuum fluctuations, conformal invariance of the gravitational coupling, UV reduction to spectral dimension 2 in position space and UV reduction to Hausdorff dimension 2 in energy-momentum space.
Charged particle motion in magnetized black holes

Valeri Frolov University of Alberta
November 21, 2013

PIRSA:13110066
Strong Gravity
There exist evidences that magnetic field in the vicinity of astrophysical black holes plays an important role. In particular it is required for explanation of such phenomenon as jet formation. Study of such problems in all their complexity requires 3D numerical simulations of the magnetohydrodynamics in a strong gravitational field. Quite often when dealing with such a complicated problem it is instructive to consider first its simplifications, which can be treated either analytically, or by integrating ordinary differential equations. Motion of a charged particle in a weakly magnetized black hole is an important example. We consider a non-rotating black hole in the weak magnetic field which is homogeneous at infinity. In the talk I discuss the following problems: How does such a magnetic field affect charged particle motion in the equatorial plane? How does it change the radius of the innermost stable circular orbits (ISCO) and period of rotation? I shall demonstratethat the magnetic field increases the efficiency of the energy extraction from the black hole and that magnetized black holes can be used as "particle accelerators". Finally, I shall discuss out-of-equatorial-plane motion and demonstrate that it is chaotic. Possible applications of these results to astrophysics are briefly discussed.
Quantum Adversary (Upper) Bound

Shelby Kimmel Massachusetts Institute of Technology (MIT)
November 20, 2013

PIRSA:13110090
Quantum Information
I discuss a technique - the quantum adversary upper bound - that uses the structure of quantum algorithms to gain insight into the quantum query complexity of Boolean functions. Using this bound, I show that there must exist an algorithm for a certain Boolean formula that uses a constant number of queries. Since the method is non-constructive, it does not give information about the form of the algorithm. After describing the technique and applying it to a class of functions, I will outline quantum algorithms that match the non-constructive bound.
Light and matter: towards macroscopic quantum systems

Jacob Taylor Office of Science and Technology Policy
November 20, 2013

PIRSA:13110060
Quantum Information
Advances in quantum engineering and material science are enabling new approaches for building systems that behave quantum mechanically on long time scales and large length scales. I will discuss how microwave and optical technologies in particular are leading to new domains of many-body physics, both classical and quantum, using photons and phonons as the constituent particles. Furthermore, I will highlight practical consequences of these advances, including improved force and acceleration sensing, efficient signal transduction, and topologically robust photonic circuits. Finally, I will consider how such large quantum systems may help us measure and constrain theories of quantum gravity and gravity-induced decoherence.
The Amplitude Mode in Condensed Matter : Higgs Hunting on a Budget

Daniel Arovas University of California, San Diego
November 19, 2013

PIRSA:13110054
Condensed Matter
The amplitude mode is a ubiquitous phenomenon in systems with broken continuous symmetry and effective relativistic dynamics, and has been observed in magnets, charge density waves, cold atom systems, and superconductors. It is a simple analog of the Higgs boson of particle physics. I will discuss the properties of the amplitude mode and its somewhat surprising visibility in two-dimensional systems, recently confirmed in cold atom experiments. The behavior in the vicinity of a quantum critical point will be stressed, comparing theoretical, numerical, and experimental results.
New Light Species and the CMB - Joint Cosmology/Particle Physics Seminar

Christopher Brust
November 19, 2013

PIRSA:13110051
Particle Physics
The effective number of neutrino species in our universe, Neff, is capable of probing the presence of new light or massless species in our universe. I will first review relevant facts about both CMB measurements of new light species and thermodynamics in the early universe. Then, I will present the effects of many models of BSM physics containing new light species on the CMB, including models containing eV-scale sterile neutrinos compatible with anomalies in neutrino experiments, and interpret the compatibility of the parameter space of these models in terms of the recent results from the Planck satellite. I will argue that the bounds on couplings obtained from the Planck measurement of the CMB are competitive with bounds coming from other areas of physics.
Topological States in Strongly-Correlated Materials

Kai Sun University of Michigan–Ann Arbor
November 15, 2013

PIRSA:13110082
Condensed Matter
In the study of strongly-correlated insulators, a long-standing puzzle remained open for over 40 years. Some Kondo insulators (or mixed-valent insulators) display strange electrical transport that cannot be understood if one assumes that it is governed by the three-dimensional bulk. In this talk, I show that some 3D Kondo insulators have the right ingredients to be topological insulators, which we called “topological Kondo insulators”. For a topological Kondo insulator, the low-temperature transport is dominated by the 2D surface rather than the 3D bulk, because the bulk of this material is an insulator while its surface is a topologically-protected 2D metal. This theoretical picture offers a natural explanation for the long-standing puzzle mentioned above. In addition, we also find that Kondo insulators can support another type of nontrivial topological structure protected by lattice symmetries, which we called “topological crystalline Kondo insulators”. In particular, we predict that SmB$_6$ is both a topological Kondo insulator and a topological crystalline Kondo insulator and I will also discuss recent experiments, which reveal the surface states in SmB$_6$.
N-body lensed CMB maps: lensing extraction and characterization

Claudia Antolini SISSA International School for Advanced Studies
November 15, 2013

PIRSA:13110088
Cosmology
After multiple high precision detections (ACT, SPT, Planck) gravitational lensing has become a new source of relevant cosmological information: combining it with other probes (e.g. the large scale structure) can give significant insight on the evolution of the Dark Energy component. Developing new algorithms of estimate of this signal will allow the community to exploit this observable as a new and independent probe in cosmology. In my talk I will present the reconstruction of the lensing shear pattern and its angular power spectrum from total intensity and polarised CMB maps obtained using Born approximated ray-tracing through N-body simulated structures.The recovered spectra are in agreement with predictions of the underlying ΛCDM with no visible bias, on a scale interval which extends from the arcminute to several degrees over the sky. This demonstrates the feasibility of CMB lensing studies based on large scale simulations of cosmological structure formation in the context of the upcoming large observational campaigns.
Finite regions, spherical entanglement, and quantum gravity

Hal Haggard Bard College
November 14, 2013

PIRSA:13110049
Quantum Gravity
An exciting frontier in physics is to understand the quantum nature of gravitation in finite regions of spacetime. Study of these regions from ``below'', that is, by studying the quantum geometry of finite regions emerging from loop gravity and spin networks has recently resulted in a new road to the quantization of volume and to evidence that there is a robust gap in the volume spectrum. In this talk I will complement these results with recent work on conformal field theories in a particular finite region, a spherical ball of space. This new view afforded from ``above" gives insights into entanglement and the Reeh-Schlieder theorem, allows calculation of the entanglement spectrum, and suggests a new route to constructing the Minkowski vacuum out of independent finite regions in quantum gravity.
Self-force and Green function in Schwarzschild spacetime via quasinormal modes and branch cut

Marc Casals Universität Leipzig
November 14, 2013

PIRSA:13110067
Strong Gravity
The modelling of gravitational wave sources is of timely interest given the exciting prospect of a first detection of gravitational waves by the new generation of detectors. The motion of a small compact object around a massive black hole deviates from a geodesic due to the action of its own field, giving rise to a self-force and the emission of gravitational waves. The self-force program has recently achieved important results using well-established methods. In this talk, we will present a different, novel method, where the self-force is calculated via the Green function of the wave equation that the field perturbation satisfies. We will present a calculation of the global Green function on Schwarzschild black hole spacetime. The calculation is carried out via a spectroscopy analysis of the Green function, which includes quasinormal modes and a branch cut in the complex-frequency plane. We will apply this analysis to calculate the self-force on a scalar charge and to reveal geometrical properties of wave propagation on a Schwarzschild background.
Bulk-boundary correspondence in PEPS

Ignacio Cirac Max Planck Institute for Gravitational Physics - Albert Einstein Institute (AEI)
November 13, 2013

PIRSA:13110058
Quantum Information
TBA
Spin and Long-Range Forces: The Unfinished Tale of the Last Massless Particle

Natalia Toro Stanford University
November 13, 2013

PIRSA:13110047
Particle Physics
The success of gauge theory descriptions of Nature follows simply, in hindsight, from Lorentz symmetry, quantum mechanics, and the existence of interacting massless particles with spin. Yet, remarkably, the most generic type of massless particle spin has never been seriously examined: Wigner's so-called "continuous spin" particles (CSPs), which have a tower of polarization states carrying all integer or half-integer helicities that mix under boosts. I will explain recent progress in understanding these particles on two fronts: simple scattering amplitudes and a free quantum field theory. The scattering amplitudes give two remarkable insights into CSP physics. First, Lorentz symmetry protects CSP interactions from the dysfunction one might expect in a theory with infinitely many polarization states: divergent cross-sections and problematic thermodynamics. Second, and most intriguingly, CSP interactions approach those of ordinary scalars or helicity-1 or 2 gauge bosons in a high-energy "correspondence" regime. While a full interacting theory of CSPs remains elusive, these results suggest that any such theory would extend Maxwell electrodynamics and/or general relativity in a viable and testable way.

Title	Speaker(s)	Date	Talk Type	Info link
Dimensional reduction in the sky		2013-11-21	Scientific Series	View details
Charged particle motion in magnetized black holes	Valeri Frolov	2013-11-21	Scientific Series	View details
Quantum Adversary (Upper) Bound	Shelby Kimmel	2013-11-20	Scientific Series	View details
Light and matter: towards macroscopic quantum systems	Jacob Taylor	2013-11-20	Scientific Series	View details
The Amplitude Mode in Condensed Matter : Higgs Hunting on a Budget	Daniel Arovas	2013-11-19	Scientific Series	View details
New Light Species and the CMB - Joint Cosmology/Particle Physics Seminar	Christopher Brust	2013-11-19	Scientific Series	View details
Topological States in Strongly-Correlated Materials	Kai Sun	2013-11-15	Scientific Series	View details
N-body lensed CMB maps: lensing extraction and characterization	Claudia Antolini	2013-11-15	Scientific Series	View details
Finite regions, spherical entanglement, and quantum gravity	Hal Haggard	2013-11-14	Scientific Series	View details
Self-force and Green function in Schwarzschild spacetime via quasinormal modes and branch cut	Marc Casals	2013-11-14	Scientific Series	View details
Bulk-boundary correspondence in PEPS	Ignacio Cirac	2013-11-13	Scientific Series	View details
Spin and Long-Range Forces: The Unfinished Tale of the Last Massless Particle	Natalia Toro	2013-11-13	Scientific Series	View details

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