Scientific Series

Displaying 3409 - 3420 of 5164

Simulating Hamiltonian evolution with quantum computers

Richard Cleve Institute for Quantum Computing (IQC)
October 16, 2013

PIRSA:13100097
Quantum Information
Can ‘sub-quantum’ theories based on a background field escape Bell’s no-go theorem ?

Louis Vervoort Université de Montréal
October 15, 2013

PIRSA:13100085
Quantum Foundations
Geometry of quantum phases and emergent Newtonian dynamics

Anatoli Polkovnikov Boston University
October 15, 2013

PIRSA:13100083
Condensed Matter
Bootstrapping the O(N) Vector Models

David Simmons-Duffin Institute for Advanced Study (IAS)
October 15, 2013

PIRSA:13100074
Quantum Fields and Strings
Including astroparticle observables in global fits to new physics scenarios

Patrick Scott McGill University
October 15, 2013

PIRSA:13100103
Particle Physics
Hybrid quantization of the Gowdy model within loop quantum cosmology

Mercedes Martin-Benito Complutense University of Madrid
October 15, 2013

PIRSA:13100102
Cosmology
Fractional solitons on the edge of the Fractional Quantum Hall states

Paul Wiegmann University of Chicago - James Franck Institute
October 10, 2013

PIRSA:13100073
Condensed Matter
Superselection Sectors in AdS/CFT - Joint Quantum Gravity and String Theory Seminar

Aron Wall University of Cambridge
October 10, 2013

PIRSA:13100066
Quantum Gravity
Plasma without Plasma: Exploring Force-Free Magnetospheres

Sam Gralla University of Arizona
October 10, 2013

PIRSA:13100078
Strong Gravity
Einstein and the Fugu

Andrew Waldron University of California, Davis
October 10, 2013

PIRSA:13100101
Cosmology
From Supersolidity to Giant Plasticity: Defects in Quantum Crystals

John Beamish University of Alberta
October 09, 2013

PIRSA:13100065
Condensed Matter
A Nearly Gaussian Hubble-patch in a non-Gaussian Universe

Marilena LoVerde University of Washington
October 08, 2013

PIRSA:13100076
Cosmology

Simulating Hamiltonian evolution with quantum computers

Richard Cleve Institute for Quantum Computing (IQC)
October 16, 2013

PIRSA:13100097
Quantum Information
In 1982, Richard Feynman proposed the concept of a quantum computer as a means of simulating physical systems that evolve according to the Schrödinger equation. I will explain various quantum algorithms that have been proposed for this simulation problem, including my recent work (jointly with Dominic Berry and Rolando Somma) that significantly improves the running time as a function of the precision of the output data.
Can ‘sub-quantum’ theories based on a background field escape Bell’s no-go theorem ?

Louis Vervoort Université de Montréal
October 15, 2013

PIRSA:13100085
Quantum Foundations
In systems described by Ising-like Hamiltonians, such as spin-lattices, the Bell Inequality can be strongly violated. Surprisingly, these systems are both local and non-superdeterministic. They are local, because 1) they include only local, near-neighbor interaction, 2) they satisfy, accordingly, the Clauser-Horne factorability condition, and 3) they can violate the Bell Inequality also in dynamic Bell experiments. Starting from this result we construct an elementary hidden-variable model, based on a generalized Ising Hamiltonian, describing the interaction of the Bell-particles with a stochastic ‘background’ medium. We suggest that such a model is a simple version of a variety of recently developed ‘sub-quantum’ theories, by authors as Nelson, Adler, De la Pena, Cetto, Groessing, Khrennikov, all based on a background field. We investigate how the model might be turned into a realistic theory. Finally, it appears that background-based models can be tested and discriminated from quantum mechanics by a straightforward extension of existing experiments.
Geometry of quantum phases and emergent Newtonian dynamics

Anatoli Polkovnikov Boston University
October 15, 2013

PIRSA:13100083
Condensed Matter
In the first part of this talk I will discuss how one can characterize geometry of quantum phases and phase transitions based on the Fubini-Study metric, which characterizes the distance between ground state wave-functions in the external parameter space. This metric is closely related to the Berry curvature. I will show that there are new geometric invariants based on the Euler characteristic. I will also show how one can directly measure this metric tensor in simple dynamical experiments. In the second part of the talk I will discuss emergent nature of macroscopic equations of motion (like Newton's equations) showing that they appear in the leading order of non-adiabatic expansion. I will show that the Berry curvature gives the Coriolis force and the Fubini-Study metric tensor is closely related to the inertia mass. Thus I will argue that any motion (not necessarily motion in space) is geometrical in nature.
Bootstrapping the O(N) Vector Models

David Simmons-Duffin Institute for Advanced Study (IAS)
October 15, 2013

PIRSA:13100074
Quantum Fields and Strings
We study the conformal bootstrap for 3D CFTs with O(N) global symmetry. We obtain rigorous upper bounds on the scaling dimensions of the first O(N) singlet and symmetric tensor operators appearing in the \phi_i x \phi_j OPE, where \phi_i is a fundamental of O(N). Comparing these bounds to previous determinations of critical exponents in the O(N) vector models, we find strong numerical evidence that the O(N) vector models saturate the bootstrap constraints at all values of N. We also compute general lower bounds on the central charge, giving numerical predictions for the values realized in the O(N) vector models. We compare our predictions to previous computations in the 1/N expansion, finding precise agreement at large values of N.
Including astroparticle observables in global fits to new physics scenarios

Patrick Scott McGill University
October 15, 2013

PIRSA:13100103
Particle Physics
Searches for physics beyond the standard model come in many forms, from terrestrial probes to astroparticle experiments and cosmological observations. Efforts to combine multiple search channels in 'global fits' to new physics scenarios typically consider only a subset of the available channels. Astroparticle searches in particular are usually only included in a very approximate way, if at all. In this talk I will review recent progress in including detailed gamma-ray, neutrino and CMB searches for dark matter in global fits. I will also preview some of the future developments and challenges in this field, where the applicability of global fits will move well beyond the small range of constrained supersymmetric models they have so far mostly been applied to.
Hybrid quantization of the Gowdy model within loop quantum cosmology

Mercedes Martin-Benito Complutense University of Madrid
October 15, 2013

PIRSA:13100102
Cosmology
Loop quantum cosmology (LQC) proposes a quantization for homogeneous cosmologies which success in solving the classical singularity problem. Realistic scenarios call for the consideration of inhomogeneities. Focusing on the simplest inhomogenous cosmological model, the Gowdy model with three-torus spatial topology and linearly polarized gravitational waves, I'll describe an approach to treat inhomogeneities in the framework of loop quantum cosmology. This is a hybrid approach that combines LQC methods with Fock quantization. Furthermore, I'll discuss justified approximations that allow us to find approximate solutions to the (very complicated) Hamiltonian constraint of the model.
Fractional solitons on the edge of the Fractional Quantum Hall states

Paul Wiegmann University of Chicago - James Franck Institute
October 10, 2013

PIRSA:13100073
Condensed Matter
We argue that dynamics of gapless Fractional Quantum Hall Edge states is essentially non-linear and that it features fractionally quantized solitons propagating along the edge. Observation of solitons would be a direct evidence of fractional charges. We show that the non-linear dynamics of the Laughlin's FQH state is governed by the quantum Benjamin-Ono equation.
Superselection Sectors in AdS/CFT - Joint Quantum Gravity and String Theory Seminar

Aron Wall University of Cambridge
October 10, 2013

PIRSA:13100066
Quantum Gravity
AdS/CFT is a duality relating the degrees of freedom in a D dimensional bulk gravity theory to a (D-1) dimensional theory living on the boundary. I will argue that in fact the boundary theory contains only a subset of the bulk observables. For each state of the boundary theory, there are multiple bulk states dual to it, which can be operationally distinguished by observers who fall across event horizons. Based on arXiv:1210.3590.
Plasma without Plasma: Exploring Force-Free Magnetospheres

Sam Gralla University of Arizona
October 10, 2013

PIRSA:13100078
Strong Gravity
Pulsars have enormous magnetic fields whose energy density dwarfs the rest mass density of their plasma magnetosphere. In this regime of a plasma, the particles drop out of the description, leaving a set of equations for the electromagnetic field alone. This non-linear, deterministic system is known as force-free electrodynamics, and turns out to have some beautiful and bizarre features. I will give a pedagogical introduction to these equations and their role in astrophysics and then discuss our recent contributions. We have taken a geometric viewpoint, using the null structure of spacetime to unify previous exact solutions and discover new ones. We have found non-stationary, non-axisymmetric solutions that describe the outer magnetosphere of pulsars, including those that are accelerated or torqued. We have derived the standard cartoon of the aligned pulsar magnetosphere from an explicit, minimal set of assumptions. Time permitting, I will also discuss some properties of black hole magnetospheres: Blandford-Znajek energy extraction, non-scattering force-free waves, and the no-ingrown-hair theorem.
Einstein and the Fugu

Andrew Waldron University of California, Davis
October 10, 2013

PIRSA:13100101
Cosmology
From Supersolidity to Giant Plasticity: Defects in Quantum Crystals

John Beamish University of Alberta
October 09, 2013

PIRSA:13100065
Condensed Matter
In 2004, Kim and Chan reported torsional oscillator experiments on 4He crystals which showed evidence of “non-classical rotational inertia”, the mass decoupling expected for a long-sought “supersolid” state. It soon became clear that this behavior is not a property of perfect crystals – defects are involved. In 2007, we made elastic measurements which showed, to our surprise, that the shear modulus of solid 4He increases dramatically below 0.2 K, with the same dependence on temperature, amplitude and 3He impurity concentration as the torsional oscillator anomaly. These shear modulus changes are due to dislocations and their interactions with impurities and vacancies. Our experiments raised an obvious question – could the torsional oscillator behavior be an artifact of the elastic changes, rather than evidence of supersolidity? During the past two years it has become clear that the answer is “yes” and interest has focused on the properties of dislocations in a quantum solid like 4He. By growing high quality single crystals in optical cells, we have now been able to explore the behavior of dislocations in 4He in unprecedented detail. In some crystals the dislocations reduce the shear modulus by more than 80%, an extraordinary effect we describe as “giant plasticity”. Solid helium has proved to be an ideal system in which to do materials science, as well as to address fundamental questions about quantum solids.
A Nearly Gaussian Hubble-patch in a non-Gaussian Universe

Marilena LoVerde University of Washington
October 08, 2013

PIRSA:13100076
Cosmology
Local-type primordial non-Gaussianity couples statistics of the curvature perturbation \zeta on vastly different physical scales. Because of this coupling, statistics (i.e. the polyspectra) of \zeta in our Hubble volume may not be representative of those in the larger universe -- that is, they may be biased. The bias depends on the local background value of \zeta, which includes contributions from all modes with wavelength k ~< H_0 and is therefore enhanced if the entire post-inflationary patch is large compared with our Hubble volume. I will discuss the bias to locally-measured statistics for general local-type non-Gaussianity. I will discuss three examples in detail: (i) the usual fNL, gNL model, (ii) a strongly non-Gaussian model with \zeta ~ \zeta_G^p, and (iii) two-field non-Gaussian initial conditions. In each scenario one may generate statistics in a Hubble-size patch that are weakly Gaussian and consistent with observations despite the fact that the statistics in the larger, post-inflationary patch look very different. Finally, I will present a worked example of how the variation in local statistics arises in the curvaton scenario.

Title	Speaker(s)	Date	Talk Type	Info link
Simulating Hamiltonian evolution with quantum computers	Richard Cleve	2013-10-16	Scientific Series	View details
Can ‘sub-quantum’ theories based on a background field escape Bell’s no-go theorem ?	Louis Vervoort	2013-10-15	Scientific Series	View details
Geometry of quantum phases and emergent Newtonian dynamics	Anatoli Polkovnikov	2013-10-15	Scientific Series	View details
Bootstrapping the O(N) Vector Models	David Simmons-Duffin	2013-10-15	Scientific Series	View details
Including astroparticle observables in global fits to new physics scenarios	Patrick Scott	2013-10-15	Scientific Series	View details
Hybrid quantization of the Gowdy model within loop quantum cosmology	Mercedes Martin-Benito	2013-10-15	Scientific Series	View details
Fractional solitons on the edge of the Fractional Quantum Hall states	Paul Wiegmann	2013-10-10	Scientific Series	View details
Superselection Sectors in AdS/CFT - Joint Quantum Gravity and String Theory Seminar	Aron Wall	2013-10-10	Scientific Series	View details
Plasma without Plasma: Exploring Force-Free Magnetospheres	Sam Gralla	2013-10-10	Scientific Series	View details
Einstein and the Fugu	Andrew Waldron	2013-10-10	Scientific Series	View details
From Supersolidity to Giant Plasticity: Defects in Quantum Crystals	John Beamish	2013-10-09	Scientific Series	View details
A Nearly Gaussian Hubble-patch in a non-Gaussian Universe	Marilena LoVerde	2013-10-08	Scientific Series	View details

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