Scientific Series

Displaying 3265 - 3276 of 5090

Quantum Many-body Dynamics with Matrix Product States

Martin Ganahl Sandbox AQ
February 24, 2014

PIRSA:14020156
Astrophysics

Condensed Matter
Sequestering the Standard Model Vacuum Energy

Nemanja Kaloper University of California, Davis
February 21, 2014

PIRSA:14020109
High Energy Physics
Quantum Raychaudhuri equation

Saurya Das University of Lethbridge
February 20, 2014

PIRSA:14020130
General Relativity & Quantum Cosmology
The Sherrington-Kirkpatrick model and its diluted version

Dmitry Panchenko Texas A&M University
February 20, 2014

PIRSA:14020151
Mathematical Physics
Causality, holography, and entanglement entropy
February 20, 2014

PIRSA:14020146
General Relativity & Quantum Cosmology

High Energy Physics

Condensed Matter

General Relativity & Quantum Cosmology
The emergent of the chiral spin liquid in kagome Heisenberg model

Dong-Ning Sheng California State University, Northridge
February 20, 2014

PIRSA:14020149
Condensed Matter
Non equilibrium thermodynamic of gravitational screens

Laurent Freidel Perimeter Institute for Theoretical Physics
February 19, 2014

PIRSA:14020144
General Relativity & Quantum Cosmology

Mathematical Physics
Psi-epistemic models are exponentially bad at explaining the distinguishability of quantum states

Matthew Leifer Chapman University
February 18, 2014

PIRSA:14020145
Quantum Physics
Cluster Polylogarithms for Scattering Amplitudes
February 18, 2014

PIRSA:14020147
High Energy Physics
Evolution of cosmological black holes: exact solutions, accretion and scalar fields

Daniel Guariento Conestoga College
February 18, 2014

PIRSA:14020150
Astrophysics
Probabilistic protocols in quantum information

Joshua Combes University of Colorado Boulder
February 13, 2014

PIRSA:14020138
Quantum Physics
Firewall evasion by quantum gravity

Ted Jacobson University of Maryland, College Park
February 13, 2014

PIRSA:14020136
General Relativity & Quantum Cosmology

Quantum Many-body Dynamics with Matrix Product States

Martin Ganahl Sandbox AQ
February 24, 2014

PIRSA:14020156
Astrophysics

Condensed Matter
The talk is divided into two parts: in the first, I will talk about dynamics of far-from equilibrium initial states in different lattice models. I will present results of quench dynamics of the XXZ-Heisenberg magnet, where interesting physics emerges after quenching the system. Then I will present results for scattering of solitonic objects in different integrable and non-integrable lattice models. In the second part, I will talk about dynamics of impurity systems. There I will talk about how impurity spectral functions can be calculated using the Chebyshev technique, and how MPS can serve as a high resolution impurity solver for Dynamical Mean-Field Theory. Finally, I will show some results for steady-state currents through a quantum dot device.
Sequestering the Standard Model Vacuum Energy

Nemanja Kaloper University of California, Davis
February 21, 2014

PIRSA:14020109
High Energy Physics
We propose a very simple reformulation of General Relativity, which completely sequesters from gravity {\it all} of the vacuum energy from a matter sector, including all loop corrections and renders all contributions from phase transitions automatically small. The idea is to make the dimensional parameters in the matter sector functionals of the 4-volume element of the universe. For them to be nonzero, the universe should be finite in spacetime. If this matter is the Standard Model of particle physics, our mechanism prevents any of its vacuum energy, classical or quantum, from sourcing the curvature of the universe. The mechanism is consistent with the large hierarchy between the Planck scale, electroweak scale and curvature scale, and early universe cosmology, including inflation. Consequences of our proposal are that the vacuum curvature of an old and large universe is not zero, but very small, that wDE≃−1 is a transient, and that the universe will collapse in the future.
Quantum Raychaudhuri equation

Saurya Das University of Lethbridge
February 20, 2014

PIRSA:14020130
General Relativity & Quantum Cosmology
We compute quantum corrections to the Raychaudhuri equation, by replacing classical geodesics with quantal (Bohmian) trajectories, and show that they prevent focusing of geodesics, and the formation of conjugate points. We discuss implications for the Hawking-Penrose singularity theorems, and for curvature singularities. Reference: arXiv: 1311.6539
The Sherrington-Kirkpatrick model and its diluted version

Dmitry Panchenko Texas A&M University
February 20, 2014

PIRSA:14020151
Mathematical Physics
I will talk about two types of random processes -- the classical Sherrington-Kirkpatrick (SK) model of spin glasses and its diluted version. One of the main motivations in these models is to find a formula for the maximum of the process, or the free energy, in the limit when the size of the system is getting large. The answer depends on understanding the structure of the Gibbs measure in a certain sense, and this structure is expected to be described by the so called Parisi solution in the SK model and Mézard-Parisi solution in the diluted SK model. I will explain what these are and mention some results in this direction.
Causality, holography, and entanglement entropy
February 20, 2014

PIRSA:14020146
General Relativity & Quantum Cosmology

High Energy Physics

Condensed Matter

General Relativity & Quantum Cosmology
After giving a brief overview of holographic entanglement entropy formulas, I will explore a curious feature they imply: when the bulk spacetime includes a black hole, the entanglement entropies often appear to depend on the spacetime geometry inside the horizon. I will ask whether this implies any loss of causality in the field theory. To answer this question, I will present a new general-relativity theorem concerning the causal structure of asymptotically AdS spacetimes, which implies an interesting relationship between bulk and boundary causal domains.
The emergent of the chiral spin liquid in kagome Heisenberg model

Dong-Ning Sheng California State University, Northridge
February 20, 2014

PIRSA:14020149
Condensed Matter
The quantum spin liquid is an emergent new state of matter, which has attracted a lot of recent attention. In particular, the time reversal symmetry broken spin liquid (Kalmeyer et. al. and Wen et. al.), characterized by the chiral ordering and fractionalized quasi-particle as a realization of the fractional quantum Hall state had been proposed for more than 20 years, but never identified as the true ground state in any more generic (e.g. Heisenberg spin exchange) models with time reversal symmetry. Here I will report two concrete examples where chiral spin liquid (CSL) emerge for a range of parameter space for kagome J1-J2-J3 (three nearest neighbors) model based on accurate density matrix renormalization group (DMRG) simulations. We identify long-range chiral ordering, ground state degeneracy, characteristic entanglement spectra, and the fractionalized topological Chern number to establish the topological state in such a system as the long-sought CSL. We further explicitly extract the modular matrix, which captures all the information of the fractional statistics of the quasi-particles in the system. I will also discuss the close relation of our model to some frustrated kagome antiferromagnets, and make a conjecture that J1 kagome model is near an unconventional critical point. I will conclude the talk with some discussions of the open directions.
Non equilibrium thermodynamic of gravitational screens

Laurent Freidel Perimeter Institute for Theoretical Physics
February 19, 2014

PIRSA:14020144
General Relativity & Quantum Cosmology

Mathematical Physics
In this talk I will review the evidence for a mysterious and deep relationship between gravitational dynamics and thermodynamics. I will show how we can extend this connection to non equilibrium thermodynamics. Using the fact that the gravitational equations are fundamentally holographic, we express them in a way that shows a deep connection between gravity and the dynamics of viscous bubbles. We will explore some aspects of this surprising correspondence.
Psi-epistemic models are exponentially bad at explaining the distinguishability of quantum states

Matthew Leifer Chapman University
February 18, 2014

PIRSA:14020145
Quantum Physics
The status of the quantum state is perhaps the most controversial issue in the foundations of quantum theory. Is it an epistemic state (representing knowledge, information, or belief) or an ontic state (a direct reflection of reality)? In the ontological models framework, quantum states correspond to probability measures over more fundamental states of reality. The quantum state is then ontic if every pair of pure states corresponds to a pair of measures that do not overlap, and is otherwise epistemic. Recently, several authors have derived theorems that aim to show that the quantum state must be ontic in this framework. Each of these theorems involve auxiliary assumptions of varying degrees of plausibility. Without such assumptions, it has been shown that models exist in which the quantum state is epistemic. However, the definition of an epistemic quantum state used in these works is extremely permissive. Only two quantum states need correspond to overlapping measures and furthermore the amount of overlap may be arbitrarily small. In order to provide an explanation of quantum phenomena such as no-cloning and the indistinguishability of pure states, the amount of overlap should be comparable to the inner product of the quantum states. In this talk, I show, without making auxiliary assumptions, that the ratio of overlap to inner product must go to zero exponentially in Hilbert space dimension for some families of states. This is done by connecting the overlap to Kochen-Specker noncontextuality, from which we infer that any contextuality inequality gives a bound on the ratio of overlap to inner product.
Cluster Polylogarithms for Scattering Amplitudes
February 18, 2014

PIRSA:14020147
High Energy Physics
Motivated by the cluster structure of two-loop scattering amplitudes in N = 4 Yang-Mills theory we define cluster polylogarithm functions. We find that all such functions of weight 4 are made up of a single simple building block associated to the A2 cluster algebra. Adding the requirement of locality on generalized Stasheff polytopes, we find that these A2 building blocks arrange themselves to form a unique function associated to the A3 cluster algebra. ThisA3 function manifests all of the cluster algebraic structure of the two-loop n-particle MHV amplitudes for all n, and we use it to provide an explicit representation for the most complicated part of the n = 7 amplitude as an example.
Evolution of cosmological black holes: exact solutions, accretion and scalar fields

Daniel Guariento Conestoga College
February 18, 2014

PIRSA:14020150
Astrophysics
Systems which contemplate the gravitational interaction between compact objects and the matter content in a cosmological environment constitute an important problem which has been studied since the early days of General Relativity. The generalized McVittie black hole is a simple exact solution to this problem, which provides us with insight on some of its known physical aspects, as well as hints to new mechanisms which arise from a formal treatment. We review some properties of this solution and its matter source, which can be interpreted as a classical fluid but is also an exact solution to a nontrivial scalar field theory.
Probabilistic protocols in quantum information

Joshua Combes University of Colorado Boulder
February 13, 2014

PIRSA:14020138
Quantum Physics
Probabilistic protocols in quantum information are an attempt to improve performance by occasionally reporting a better result than could be expected from a deterministic protocol. Here we show that probabilistic protocols can never improve performance beyond the quantum limits on the corresponding deterministic protocol. To illustrate this result we examine three common probabilistic protocols: probabilistic amplification, weak value amplification, and probabilistic metrology. In each of these protocols we show explicitly that the optimal deterministic protocol is better than the corresponding probabilistic protocol when the probabilistic nature of the protocol is correctly accounted for.
Firewall evasion by quantum gravity

Ted Jacobson University of Maryland, College Park
February 13, 2014

PIRSA:14020136
General Relativity & Quantum Cosmology
It has been argued that if black hole evaporation is a unitary quantum process, then a black hole horizon must be cloaked by a "firewall", i.e. a highly excited state of local quantum fields. This reasoning is based on factorizing the Hilbert space into interior and exterior degrees of freedom. Such factorization ignores the Wheeler-deWitt constraint equation, which arises from the diffeomorphism invariance of quantum gravity. I will argue that this constraint evades the firewall.

Title	Speaker(s)	Date	Talk Type	Info link
Quantum Many-body Dynamics with Matrix Product States	Martin Ganahl	2014-02-24	Scientific Series	View details
Sequestering the Standard Model Vacuum Energy	Nemanja Kaloper	2014-02-21	Scientific Series	View details
Quantum Raychaudhuri equation	Saurya Das	2014-02-20	Scientific Series	View details
The Sherrington-Kirkpatrick model and its diluted version	Dmitry Panchenko	2014-02-20	Scientific Series	View details
Causality, holography, and entanglement entropy		2014-02-20	Scientific Series	View details
The emergent of the chiral spin liquid in kagome Heisenberg model	Dong-Ning Sheng	2014-02-20	Scientific Series	View details
Non equilibrium thermodynamic of gravitational screens	Laurent Freidel	2014-02-19	Scientific Series	View details
Psi-epistemic models are exponentially bad at explaining the distinguishability of quantum states	Matthew Leifer	2014-02-18	Scientific Series	View details
Cluster Polylogarithms for Scattering Amplitudes		2014-02-18	Scientific Series	View details
Evolution of cosmological black holes: exact solutions, accretion and scalar fields	Daniel Guariento	2014-02-18	Scientific Series	View details
Probabilistic protocols in quantum information	Joshua Combes	2014-02-13	Scientific Series	View details
Firewall evasion by quantum gravity	Ted Jacobson	2014-02-13	Scientific Series	View details

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Format results

Quantum Many-body Dynamics with Matrix Product States

Sequestering the Standard Model Vacuum Energy

Quantum Raychaudhuri equation

The Sherrington-Kirkpatrick model and its diluted version

Causality, holography, and entanglement entropy

The emergent of the chiral spin liquid in kagome Heisenberg model

Non equilibrium thermodynamic of gravitational screens

Psi-epistemic models are exponentially bad at explaining the distinguishability of quantum states

Cluster Polylogarithms for Scattering Amplitudes

Evolution of cosmological black holes: exact solutions, accretion and scalar fields

Probabilistic protocols in quantum information

Firewall evasion by quantum gravity

Quantum Many-body Dynamics with Matrix Product States

Sequestering the Standard Model Vacuum Energy

Quantum Raychaudhuri equation

The Sherrington-Kirkpatrick model and its diluted version

Causality, holography, and entanglement entropy

The emergent of the chiral spin liquid in kagome Heisenberg model

Non equilibrium thermodynamic of gravitational screens

Psi-epistemic models are exponentially bad at explaining the distinguishability of quantum states

Cluster Polylogarithms for Scattering Amplitudes

Evolution of cosmological black holes: exact solutions, accretion and scalar fields

Probabilistic protocols in quantum information

Firewall evasion by quantum gravity