Learning the non-equilibrium dynamics of Brownian movies

Abstract Time-lapse microscopy imaging provides direct access to the dynamics of soft and living systems. At mesoscopic scales, such microscopy experiments reveal intrinsic thermal and non-equilibrium fluctuations. These fluctuations, together with measurement noise, pose a challenge for the dynamical analysis of these Brownian movies. Traditionally, methods to analyze such experimental data rely on tracking embedded or endogenous probes. However, it is in general unclear, especially in complex many-body systems, which degrees of freedom are the most informative about their non-equilibrium nature. Here, we introduce an alternative, tracking-free approach that overcomes these difficulties via an unsupervised analysis of the Brownian movie. We develop a dimensional reduction scheme selecting a basis of modes based on dissipation. Subsequently, we learn the non-equilibrium dynamics, thereby estimating the entropy production rate and time-resolved force maps. After benchmarking our method against a minimal model, we illustrate its broader applicability with an example inspired by active biopolymer gels.

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Epidemic growth and Griffiths effects on an emergent network of excited atoms

Nature Communications ◽

10.1038/s41467-020-20333-7 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

T. M. Wintermantel ◽

M. Buchhold ◽

S. Shevate ◽

M. Morgado ◽

Y. Wang ◽

...

Keyword(s):

Complex Systems ◽

Power Laws ◽

Excitation Density ◽

Griffiths Phase ◽

Many Body ◽

Excited Atoms ◽

Equilibrium Dynamics ◽

Many Body Systems ◽

Excitation Number ◽

Non Equilibrium

AbstractWhether it be physical, biological or social processes, complex systems exhibit dynamics that are exceedingly difficult to understand or predict from underlying principles. Here we report a striking correspondence between the excitation dynamics of a laser driven gas of Rydberg atoms and the spreading of diseases, which in turn opens up a controllable platform for studying non-equilibrium dynamics on complex networks. The competition between facilitated excitation and spontaneous decay results in sub-exponential growth of the excitation number, which is empirically observed in real epidemics. Based on this we develop a quantitative microscopic susceptible-infected-susceptible model which links the growth and final excitation density to the dynamics of an emergent heterogeneous network and rare active region effects associated to an extended Griffiths phase. This provides physical insights into the nature of non-equilibrium criticality in driven many-body systems and the mechanisms leading to non-universal power-laws in the dynamics of complex systems.

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Non-equilibrium dynamics of an ultracold Bose gas under multi-pulsed interaction quenches

Modern Physics Letters B ◽

10.1142/s021798491650367x ◽

2016 ◽

Vol 30 (30) ◽

pp. 1650367 ◽

Cited By ~ 1

Author(s):

Lei Chen ◽

Zhidong Zhang ◽

Zhaoxin Liang

Keyword(s):

Bose Gas ◽

Quantum Gases ◽

Zero Temperature ◽

Many Body ◽

Equilibrium Dynamics ◽

Many Body Systems ◽

Multiple Interaction ◽

The One ◽

Body Correlation ◽

Non Equilibrium

We investigate the non-equilibrium properties of a weakly interacting Bose gas subjected to a multi-pulsed quench at zero temperature, where the interaction parameter in the Hamiltonian system switches between values [Formula: see text] and [Formula: see text] for multiple times. The one-body and two-body correlation functions as well as Tan’s contact are calculated. The quench induced excitations are shown to increase with the number of quenches for both [Formula: see text] and [Formula: see text]. This implies the possibility to use multi-pulsed quantum quench as a more powerful way as compared to the “one-off” quench in controllable explorations of non-equilibrium quantum many-body systems. In addition, we study the ultra-short-range property of the two-body correlation function after multiple interaction quenches, which can serve as a probe of the “Tan’s contact” in the experiments. Our findings allow for an experimental probe using state of the art techniques with ultracold quantum gases.

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Towards a Theory of Quantum Gravity from Neural Networks

Entropy ◽

10.3390/e24010007 ◽

2021 ◽

Vol 24 (1) ◽

pp. 7

Author(s):

Vitaly Vanchurin

Keyword(s):

Neural Network ◽

Degrees Of Freedom ◽

Space Time ◽

Learning System ◽

Einstein Equations ◽

Localized States ◽

Batch Size ◽

Step Size ◽

Equilibrium Dynamics ◽

Non Equilibrium

Neural network is a dynamical system described by two different types of degrees of freedom: fast-changing non-trainable variables (e.g., state of neurons) and slow-changing trainable variables (e.g., weights and biases). We show that the non-equilibrium dynamics of trainable variables can be described by the Madelung equations, if the number of neurons is fixed, and by the Schrodinger equation, if the learning system is capable of adjusting its own parameters such as the number of neurons, step size and mini-batch size. We argue that the Lorentz symmetries and curved space-time can emerge from the interplay between stochastic entropy production and entropy destruction due to learning. We show that the non-equilibrium dynamics of non-trainable variables can be described by the geodesic equation (in the emergent space-time) for localized states of neurons, and by the Einstein equations (with cosmological constant) for the entire network. We conclude that the quantum description of trainable variables and the gravitational description of non-trainable variables are dual in the sense that they provide alternative macroscopic descriptions of the same learning system, defined microscopically as a neural network.

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Scaling approach to quantum non-equilibrium dynamics of many-body systems

New Journal of Physics ◽

10.1088/1367-2630/12/11/113005 ◽

2010 ◽

Vol 12 (11) ◽

pp. 113005 ◽

Cited By ~ 51

Author(s):

Vladimir Gritsev ◽

Peter Barmettler ◽

Eugene Demler

Keyword(s):

Many Body ◽

Equilibrium Dynamics ◽

Many Body Systems ◽

Non Equilibrium

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Temperature chaos is present in off-equilibrium spin-glass dynamics

Communications Physics ◽

10.1038/s42005-021-00565-9 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Marco Baity-Jesi ◽

Enrico Calore ◽

Andrés Cruz ◽

Luis Antonio Fernandez ◽

José Miguel Gil-Narvion ◽

...

Keyword(s):

Spin Glass ◽

Dynamic Effect ◽

Large Degree ◽

Equilibrium Temperature ◽

Experimental Conditions ◽

Temperature Changes ◽

Equilibrium Dynamics ◽

Glass Dynamics ◽

Extreme Sensitivity ◽

Non Equilibrium

AbstractExperiments featuring non-equilibrium glassy dynamics under temperature changes still await interpretation. There is a widespread feeling that temperature chaos (an extreme sensitivity of the glass to temperature changes) should play a major role but, up to now, this phenomenon has been investigated solely under equilibrium conditions. In fact, the very existence of a chaotic effect in the non-equilibrium dynamics is yet to be established. In this article, we tackle this problem through a large simulation of the 3D Edwards-Anderson model, carried out on the Janus II supercomputer. We find a dynamic effect that closely parallels equilibrium temperature chaos. This dynamic temperature-chaos effect is spatially heterogeneous to a large degree and turns out to be controlled by the spin-glass coherence length ξ. Indeed, an emerging length-scale ξ* rules the crossover from weak (at ξ ≪ ξ*) to strong chaos (ξ ≫ ξ*). Extrapolations of ξ* to relevant experimental conditions are provided.

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Probing the interplay between lattice dynamics and short-range magnetic correlations in CuGeO3 with femtosecond RIXS

npj Quantum Materials ◽

10.1038/s41535-021-00350-5 ◽

2021 ◽

Vol 6 (1) ◽

Author(s):

E. Paris ◽

C. W. Nicholson ◽

S. Johnston ◽

Y. Tseng ◽

M. Rumo ◽

...

Keyword(s):

Short Range ◽

Degrees Of Freedom ◽

Time Resolved ◽

Model Calculations ◽

Spin Correlations ◽

Singlet Exciton ◽

Magnetic Correlations ◽

Local Lattice ◽

Frustrated Systems ◽

A Charge

AbstractInvestigations of magnetically ordered phases on the femtosecond timescale have provided significant insights into the influence of charge and lattice degrees of freedom on the magnetic sub-system. However, short-range magnetic correlations occurring in the absence of long-range order, for example in spin-frustrated systems, are inaccessible to many ultrafast techniques. Here, we show how time-resolved resonant inelastic X-ray scattering (trRIXS) is capable of probing such short-ranged magnetic dynamics in a charge-transfer insulator through the detection of a Zhang–Rice singlet exciton. Utilizing trRIXS measurements at the O K-edge, and in combination with model calculations, we probe the short-range spin correlations in the frustrated spin chain material CuGeO3 following photo-excitation, revealing a strong coupling between the local lattice and spin sub-systems.

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A time-domain phase diagram of metastable states in a charge ordered quantum material

Nature Communications ◽

10.1038/s41467-021-22646-7 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Jan Ravnik ◽

Michele Diego ◽

Yaroslav Gerasimenko ◽

Yevhenii Vaskivskyi ◽

Igor Vaskivskyi ◽

...

Keyword(s):

Phase Diagram ◽

Time Domain ◽

Metastable States ◽

Scanning Tunneling ◽

Photon Density ◽

Tunneling Microscopy ◽

Equilibrium Conditions ◽

Time Resolved ◽

A Charge ◽

Non Equilibrium

AbstractMetastable self-organized electronic states in quantum materials are of fundamental importance, displaying emergent dynamical properties that may be used in new generations of sensors and memory devices. Such states are typically formed through phase transitions under non-equilibrium conditions and the final state is reached through processes that span a large range of timescales. Conventionally, phase diagrams of materials are thought of as static, without temporal evolution. However, many functional properties of materials arise as a result of complex temporal changes in the material occurring on different timescales. Hitherto, such properties were not considered within the context of a temporally-evolving phase diagram, even though, under non-equilibrium conditions, different phases typically evolve on different timescales. Here, by using time-resolved optical techniques and femtosecond-pulse-excited scanning tunneling microscopy (STM), we track the evolution of the metastable states in a material that has been of wide recent interest, the quasi-two-dimensional dichalcogenide 1T-TaS2. We map out its temporal phase diagram using the photon density and temperature as control parameters on timescales ranging from 10−12 to 103 s. The introduction of a time-domain axis in the phase diagram enables us to follow the evolution of metastable emergent states created by different phase transition mechanisms on different timescales, thus enabling comparison with theoretical predictions of the phase diagram, and opening the way to understanding of the complex ordering processes in metastable materials.

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Ultrafast dynamical Lifshitz transition

Science Advances ◽

10.1126/sciadv.abd9275 ◽

2021 ◽

Vol 7 (17) ◽

pp. eabd9275

Author(s):

Samuel Beaulieu ◽

Shuo Dong ◽

Nicolas Tancogne-Dejean ◽

Maciej Dendzik ◽

Tommaso Pincelli ◽

...

Keyword(s):

Fermi Surface ◽

Colossal Magnetoresistance ◽

Surface Topology ◽

Strongly Correlated ◽

Many Body ◽

Time Resolved ◽

Weyl Semimetal ◽

Lifshitz Transition ◽

Fermi Surface Topology ◽

Many Body Systems

Fermi surface is at the heart of our understanding of metals and strongly correlated many-body systems. An abrupt change in the Fermi surface topology, also called Lifshitz transition, can lead to the emergence of fascinating phenomena like colossal magnetoresistance and superconductivity. While Lifshitz transitions have been demonstrated for a broad range of materials by equilibrium tuning of macroscopic parameters such as strain, doping, pressure, and temperature, a nonequilibrium dynamical route toward ultrafast modification of the Fermi surface topology has not been experimentally demonstrated. Combining time-resolved multidimensional photoemission spectroscopy with state-of-the-art TDDFT+U simulations, we introduce a scheme for driving an ultrafast Lifshitz transition in the correlated type-II Weyl semimetal Td-MoTe2. We demonstrate that this nonequilibrium topological electronic transition finds its microscopic origin in the dynamical modification of the effective electronic correlations. These results shed light on a previously unexplored ultrafast scheme for controlling the Fermi surface topology in correlated quantum materials.

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