Conference

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New Vacuum and Representation For Loop Quantum Gravity

Bianca Dittrich Perimeter Institute for Theoretical Physics

May 21, 2014

PIRSA:14050119
(Lea Santos) General Features of the Relaxation Dynamics of Isolated Interacting Quantum Systems

May 16, 2014

PIRSA:14050088
Quench dynamics in interacting and disordered field theories in one-dimension

Aditi Mitra New York University (NYU)

May 16, 2014

PIRSA:14050087
(Robert Konik) Glimmers of a Quantum KAM Theorem: Insights from Quantum Quenches in One Dimensional Bose Gases

May 16, 2014

PIRSA:14050086
TBA

Antonello Scardicchio The Abdus Salam International Centre for Theoretical Physics (ICTP)

May 15, 2014

PIRSA:14050084
Can Eigenstate Thermalization Breakdown without Disorder?

Matthew Fisher University of California, Santa Barbara

May 15, 2014

PIRSA:14050083
Universal dynamics and topological order in many-body localized states

Ronen Vosk Weizmann Institute of Science

May 15, 2014

PIRSA:14050082
(Jean-Sebastien Caux) Exact solutions for quenches in 1d Bose gases and quantum spin chains

May 15, 2014

PIRSA:14050081
A Rigorous Result on Many-Body Localization

John Imbrie University of Virginia

May 14, 2014

PIRSA:14050079
Many-body mobility edge in a mean-field quantum spin-glass

Arijeet Pal Harvard University

May 14, 2014

PIRSA:14050078
Localization and topology protected quantum coherence at the edge of 'hot' matter

Ehud Altman University of California, Berkeley

May 14, 2014

PIRSA:14050077
Long-time behavior of periodically driven isolated interacting quantum systems

Luca D'Alessio Boston University

May 13, 2014

PIRSA:14050073

New Vacuum and Representation For Loop Quantum Gravity

Bianca Dittrich Perimeter Institute for Theoretical Physics

May 21, 2014

PIRSA:14050119
(Lea Santos) General Features of the Relaxation Dynamics of Isolated Interacting Quantum Systems

May 16, 2014

PIRSA:14050088

We consider isolated interacting quantum systems that are taken out of equilibrium instantaneously (quenched). We study numerically and analytically the probability of finding the initial state later on in time (the so-called fidelity or Loschmidt echo), the relaxation time of the system, and the evolution of few-body observables. The fidelity decays fastest for systems described by full random matrices, where simultaneous many-body interactions are implied. In the realm of realistic systems with two-body interactions, the dynamics is slower and dependent on the energy of the initial state. The fastest fidelity decay in this case is Gaussian and can persist until saturation. The fidelity also plays a central role in the short-time dynamics of few-body observables that commute with the system Hamiltonian before the quench. Our analyses are mainly developed for initial states that can be prepared in experiments with cold atoms in optical lattices.
Quench dynamics in interacting and disordered field theories in one-dimension

Aditi Mitra New York University (NYU)

May 16, 2014

PIRSA:14050087

I will present results for the quench dynamics of one-dimensional interacting bosons under two circumstances. One is when the bosons are in the vicinity of the superfluid-Mott quantum critical point, while the second is when the bosons are in a disordered potential which can drive the system into a Bose glass phase. I will show that the dynamics following a quench can be quite complex by being characterized by three regimes. One is a short time perturbatively accessible regime which depends on microscopic parameters, the second is an intermediate time prethermalized regime where inelastic effects are weak and correlation functions can show universal scaling behavior which is quantified by a nonequilibrium generalization of the Callan-Symanzik equations. The third is a long time regime where inelastic effects become important. For the dynamics in the inelastic regime I will construct a novel quantum kinetic equation that accounts for multi-particle scattering between bosons, and discuss how the combined effect of interactions and (weak) disorder can thermalize the system.
(Robert Konik) Glimmers of a Quantum KAM Theorem: Insights from Quantum Quenches in One Dimensional Bose Gases

May 16, 2014

PIRSA:14050086

We consider quantum quenches in one dimensional Bose gases where we prepare the gas in the ground state of a parabolic trap and then release it into a small cosine potential. This cosine potential breaks the integrability of the 1D gas which absent the potential is described by the Lieb-Liniger model. We explore the consequences of this cosine potential on the thermalization of the gas. We argue that the integrability breaking of the cosine does not immediately lead to ergodicity inasmuch as we demonstrate that there are residual quasi-conserved quantities post-quench. We demonstrate that the quality of this quasi-conservation can be made arbitrarily good.
TBA

Antonello Scardicchio The Abdus Salam International Centre for Theoretical Physics (ICTP)

May 15, 2014

PIRSA:14050084
Can Eigenstate Thermalization Breakdown without Disorder?

Matthew Fisher University of California, Santa Barbara

May 15, 2014

PIRSA:14050083

We describe a new diagnostic for many-body wavefunctions which generalizes the spatial bipartite entanglement entropy. By was of illustration, for a two-component wavefunction of heavy and light particles, a partial (projective) measurement of the coordinates of the heavy (but not light) particles is first performed, and then the entanglement entropy of the projected wavefunction for the light particles is computed. If the two-component wavefunction has a volume law entanglement entropy, yet the post measurement wavefunction of the light particles is disentangled with an area law entanglement, we refer to the original wavefunction as a “Quantum Disentangled State”. This diagnostic can be generalized to include other partial measurements, such as measuring the charge, but not spin, for finite-energy density eigenstates of Fermion Hubbard-type model. Quantum disentanglement results if the post measurement spin-wavefunction has an area law entanglement entropy. Recent numerics searching for such Quantum Disentangled States in 1d Hubbard-type models will be discussed in detail.
Universal dynamics and topological order in many-body localized states

Ronen Vosk Weizmann Institute of Science

May 15, 2014

PIRSA:14050082

It has been argued recently that, through a phenomenon of many-body localization, closed quantum systems subject to sufficiently strong disorder would fail to thermalize. In this talk I will describe a real time renormalization group approach, which offers a controlled description of universal dynamics in the localized phase. In particular it explains the ultra-slow entanglement propagation in this state and identifies the emergent conserved quantities which prevent thermalization. The RG analysis also shows, that far from being a trivial dead state, the MBL state admits phase transitions between distinct dynamical phases. For example, I will discuss the universal aspects of a transition between a paramagnetic localized state to one which exhibits spin-glass order. Finally, I will present a development of the RG scheme, defined on an effective coarse grained model, which allows to capture the transition from a many-body localized to a thermalizing state.
(Jean-Sebastien Caux) Exact solutions for quenches in 1d Bose gases and quantum spin chains

May 15, 2014

PIRSA:14050081
A Rigorous Result on Many-Body Localization

John Imbrie University of Virginia

May 14, 2014

PIRSA:14050079

I will discuss a proof of many-body localization for a one-dimensional spin chain with random local interactions. The proof depends on a physically reasonable assumption that limits the amount of level attraction in the system. I construct a sequence of local rotations that completely diagonalizes the Hamiltonian and exhibits the local degrees of freedom.
Many-body mobility edge in a mean-field quantum spin-glass

Arijeet Pal Harvard University

May 14, 2014

PIRSA:14050078

Isolated, interacting quantum systems in the presence of strong disorder can exist in a many-body localized phase where the assumptions of equilibrium statistical physics are violated. On tuning either the parameters of the Hamiltonian or the energy density, the system is expected to transition into the ergodic phase. While the transition at "infinite temperature" as a function of system parameters has been found numerically but, the transition tuned by energy density has eluded such methods.
In my talk I will discuss the nature of the many-body localization-delocalization (MBLD) transition as a function of energy denisty in the quantum random energy model (QREM). QREM provides a mean-field description of the equilibrium spin glass transition. We show that it further exhibits a many-body mobility edge when viewed as a closed quantum system. The mean-field structure of the model allows an analytically tractable description of the MBLD transition. I will also comment on the nature of the critical states in this mean-field model.
This opens the possibility of developing a mean-field theory of this interesting dynamical phase transition.
Localization and topology protected quantum coherence at the edge of 'hot' matter

Ehud Altman University of California, Berkeley

May 14, 2014

PIRSA:14050077

Topological phases are often characterized by special edge states confined near the boundaries by an energy gap in the bulk. On raising temperature, these edge states are lost in a clean system due to mobile thermal excitations. Recently however, it has been established that disorder can localize an isolated many body system, potentially allowing for a sharply defined topological phase even in a highly excited state.I will show this to be the case for the topological phase of a one dimensional magnet with quenched disorder, which features spin one-half excitations at the edges. The time evolution of a simple, highly excited, initial state is used to reveal quantum coherent edge spins. In particular, I will demonstrate, using theoretical arguments and numerical simulation, the coherent revival of an edge spin over a time scale that grows exponentially bigger with system size. This is in sharp contrast to the general expectation that quantum bits strongly coupled to a 'hot' many body system will rapidly lose coherence.
Long-time behavior of periodically driven isolated interacting quantum systems

Luca D'Alessio Boston University

May 13, 2014

PIRSA:14050073

We show that generic interacting quantum systems, which are isolated and finite, periodically driven by sudden quenches exhibit three physical regimes. For short driving periods the Floquet Hamiltonian is well approximated by the time-averaged Hamiltonian, while for long periods the evolution operator exhibits properties of random matrices of a Circular Ensemble (CE). In-between, there is a crossover
regime. We argue that, in the thermodynamic limit and for nonvanishing driving periods, the evolution operator always exhibits properties of CE random matrices. Consequently, driving leads to infinite temperature at infinite time and to an unphysical Floquet Hamiltonian.

Title	Speaker(s)	Date	Talk Type	Info link
New Vacuum and Representation For Loop Quantum Gravity	Bianca Dittrich	2014-05-21	Conference	View details
(Lea Santos) General Features of the Relaxation Dynamics of Isolated Interacting Quantum Systems		2014-05-16	Conference	View details
Quench dynamics in interacting and disordered field theories in one-dimension	Aditi Mitra	2014-05-16	Conference	View details
(Robert Konik) Glimmers of a Quantum KAM Theorem: Insights from Quantum Quenches in One Dimensional Bose Gases		2014-05-16	Conference	View details
TBA	Antonello Scardicchio	2014-05-15	Conference	View details
Can Eigenstate Thermalization Breakdown without Disorder?	Matthew Fisher	2014-05-15	Conference	View details
Universal dynamics and topological order in many-body localized states	Ronen Vosk	2014-05-15	Conference	View details
(Jean-Sebastien Caux) Exact solutions for quenches in 1d Bose gases and quantum spin chains		2014-05-15	Conference	View details
A Rigorous Result on Many-Body Localization	John Imbrie	2014-05-14	Conference	View details
Many-body mobility edge in a mean-field quantum spin-glass	Arijeet Pal	2014-05-14	Conference	View details
Localization and topology protected quantum coherence at the edge of 'hot' matter	Ehud Altman	2014-05-14	Conference	View details
Long-time behavior of periodically driven isolated interacting quantum systems	Luca D'Alessio	2014-05-13	Conference	View details

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