Max Planck Institute for Dynamics and Self-Organization

www.ds.mpg.de
Gottingen, Germany

The Max Planck Institute for Dynamics and Self-Organization in Göttingen, Germany, is a research institute for investigations of complex non-equilibrium systems, particularly in physics and biology.Its founding history goes back to Ludwig Prandtl who in 1911 requested a Kaiser Wilhelm Institute to be founded for the investigation of aerodynamics and hydrodynamics. As a first step the Aeronautische Versuchsanstalt was established in 1915 and then finally the Kaiser Wilhelm Institute for Flow Research was established in 1924. In 1948 it became part of the Max Planck Society. The Max Planck Society was founded in this institute. In 2003 it was renamed to Max Planck Institute for Dynamics and Self-Organization. It is one of 80 institutes in the Max Planck Society . Wikipedia.


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In 1665, the Dutch researcher Christiaan Huygens (1629-1695) was working on a novel clock for ships. At the time, pendulum clocks were the state of the art, and a specially shaped pendulum was intended to respond less sensitively to the rocking of the ships. Ship's clocks working as precisely as possible were the key to exact determining longitude. For protection, Huygens had built two of his pendulum clocks into a heavy housing, which was suspended such that it should largely compensate the rocking of the ship. He then discovered a surprising phenomenon: Although the clocks ran independently of each other and were not subject to any external influence, their pendulums swung in precise synchrony within at most half an hour after each restart. Huygens surmised even back then that the two pendulums synchronized via tiny "imperceptible motions" in the joint suspension of the two clocks. His guess was correct, as physicists were later able to demonstrate for such oscillating systems. "One can observe such clocks as well as manyother oscillating objects to synchronize with each other even in the absence of any external influence," explains Marc Timme, theoretical physicist at the Max Planck Institute for Dynamics and Self-Organization in Göttingen. The professor heads a Research Group that studies the dynamics of networks and analyses, for example, the behaviour of electricity grids. A joint suspension causes the pendulums to synchronize The self-organized synchronization of seemingly independent oscillators to one frequency can be observed in many systems in nature and engineering. The prerequisite is often a "hidden" coupling, as via the joint suspension for the pendulum clocks. Scientists like Timme also call this a locking behaviour, with all oscillators involved synchronizing to precisely one frequency and then remaining trapped in it. This actually works with children's swings suspended from a joint beam as well. If they are pushed off from different starting positions, they may synchronize to a single frequency at some stage. The examples are not limited only to mechanical oscillations. "Synchronization alsohappens for many different biological networks," explains Timme "The phenomenon for instance occurs in the brain when nerve impulses synchronize." This synchronization of brain waves in certain areas seems to be important for the working of our thinking organ. But it can also achieve too much. "Large-scale, extensive synchronization of brain waves in the brain is characteristic for epilepsy," says Timme. All these self-organized ordering phenomena are based on the fundamentals of the classical – non-quantum world. However, a German-Italian research collaboration has now discovered synchronization emerging even for pure quantum systems. This collaboration was initiated by Marc Timme together with his former postdoc Dirk Witthaut, who in the meantime heads an independent research group at the Forschungszentrum Jülich. The conceptually new work has now been published in the renowned Nature Communications journal. In the publication, the scientists demonstrate for the first time that isolated systems comprising large numbers of quantum objects, such as the atoms of a Bose-Einstein condensate which is trapped in an optical lattice, for example, can synchronize in a very similar way to classical systems of physics. In a Bose-Einstein condensates, whose experimental realization was honoured with the Nobel Prize in physics in 2001, several atoms behave like a single quantum object, individual atoms can nevertheless be trapped in an optical lattice. Such grids are constructed from the electromagnetic potential of crossed laser beams and resemble an egg box made of light, in which the atoms are spread out. The quantum particles can synchronize in the box without any external influence whatsoever, meaning they are likewise self-organized. "This is the main news of our article," says Timme. These oscillating quantum systems can be imagined as manyHuygens' pendulum clocks. These clocks were coupled with each other via a beam, from which they are all suspended. In consequence, their pendulums oscillate synchronously after some time. The quantum systems synchronize in just the same way by interacting with each other. This self-organized transition to a synchronized collective is in complete correspondence with classical physics. But something more happens in the quantum world – a collective quantum state forms. This quantum state represents the uncertainty of quantum mechanics as such: entanglement. Quantum systems which are entangled with each other can no longer be described independently of each other. In our example of the clocks this would be roughly as if it were no longer possible to recognize the pendulums individually – each pendulum would contain information on all the others. All pendulums would therefore behave together like one object, a quantum object. "Classical synchronization is the 'smoking gun' for the formation of quantum mechanical entanglement," says Dirk Witthaut, lead author of the study, "and this is extremely surprising." This finding throws new light onto the fascinating phenomenon of entanglement. Entangled systems have been routinely produced in many physics laboratories for decades. The new results are not just important for basic research. For some time now the quantum information research field has been working on using entanglement as a technical resource, be it in quantum computers of the future or in the error-proof transmission of information. The article now published by the German-Italian collaboration also makes concrete proposals as to how the self-organized synchronization of a quantum collective can be detected in the laboratory. It will therefore be fascinating to see in which form the phenomenon really shows up and how it inspires new lines of research. For Marc Timme, this paper is also evidence of how important the collaboration between different disciplines is in making such unusual discoveries. He himself is an expert on the dynamics of classical self-organizing systems and synchronization in particular. His research fields are known as "nonlinear dynamics" and "network dynamics", the former of which has also become widely known as "chaos theory". Dirk Witthaut in contrast comes from the area of quantum physics. Only the intense collaboration of the two schools of thought in physics led to the discovery that classical synchronization in the quantum world has something to do with quantum mechanical entanglement. "It is often very difficult to fund and carry out such interdisciplinary projects in particular, because they cannot be assigned to any of the traditional disciplines," says Timme. The success in Göttingen was only possible because the Max Planck Society supported this interdisciplinary research in the long term and as pure research without a predefined goal. More information: Dirk Witthaut et al. Classical synchronization indicates persistent entanglement in isolated quantum systems, Nature Communications (2017). DOI: 10.1038/ncomms14829


Seiden G.,Max Planck Institute for Dynamics and Self-Organization | Seiden G.,Weizmann Institute of Science | Thomas P.J.,University of Warwick
Reviews of Modern Physics | Year: 2011

Rotating-drum flows span a variety of research areas, ranging from physics of granular matter through hydrodynamics of suspensions to pure liquid coating flows. Recent years have seen an intensified scientific activity associated with this unique geometrical configuration, which has contributed to our understanding of related subjects such as avalanches in granules and segregation in suspensions. The existing literature related to rotating-drum flows is reviewed, highlighting similarities and differences between the various flow realizations. Scaling laws expressing the importance of different mechanisms underlying the observed phenomena have been focused on. An emphasis is placed on pattern formation phenomena. Rotating-drum flows exhibit stationary patterns as well as traveling and oscillating patterns; they exhibit reversible transitions as well as hysteresis. Apart from the predominant cylindrical configuration, this review covers recent work done with tumblers having other geometries, such as the sphere and the Hele-Shaw cell. © 2011 American Physical Society.


Holzner M.,Max Planck Institute for Dynamics and Self-Organization | Luthi B.,ETH Zurich
Physical Review Letters | Year: 2011

In this Letter we present results from particle tracking velocimetry and direct numerical simulation that are congruent with the existence of a laminar superlayer, as proposed in the pioneering work of Corrsin and Kistler (NACA, Technical Report No.AA1244, 1955). We find that the local superlayer velocity is dominated by a viscous component and its magnitude is comparable to the characteristic velocity of the smallest scales of motion. This slow viscous process involves a large surface area so that the global rate of turbulence spreading is set by the largest scales of motion. These findings are important for a better understanding of mixing of mass and momentum in a variety of flows where thin layers of shear exist. Examples are boundary layers, clouds, planetary atmospheres, and oceans. © 2011 American Physical Society.


Lohse D.,University of Twente | Lohse D.,Max Planck Institute for Dynamics and Self-Organization | Zhang X.,University of Twente | Zhang X.,RMIT University
Reviews of Modern Physics | Year: 2015

Surface nanobubbles are nanoscopic gaseous domains on immersed substrates which can survive for days. They were first speculated to exist about 20 years ago, based on stepwise features in force curves between two hydrophobic surfaces, eventually leading to the first atomic force microscopy (AFM) image in 2000. While in the early years it was suspected that they may be an artifact caused by AFM, meanwhile their existence has been confirmed with various other methods, including through direct optical observation. Their existence seems to be paradoxical, as a simple classical estimate suggests that they should dissolve in microseconds, due to the large Laplace pressure inside these nanoscopic spherical-cap-shaped objects. Moreover, their contact angle (on the gas side) is much smaller than one would expect from macroscopic counterparts. This review will not only give an overview on surface nanobubbles, but also on surface nanodroplets, which are nanoscopic droplets (e.g., of oil) on (hydrophobic) substrates immersed in water, as they show similar properties and can easily be confused with surface nanobubbles and as they are produced in a similar way, namely, by a solvent exchange process, leading to local oversaturation of the water with gas or oil, respectively, and thus to nucleation. The review starts with how surface nanobubbles and nanodroplets can be made, how they can be observed (both individually and collectively), and what their properties are. Molecular dynamic simulations and theories to account for the long lifetime of the surface nanobubbles are then reported on. The crucial element contributing to the long lifetime of surface nanobubbles and nanodroplets is pinning of the three-phase contact line at chemical or geometric surface heterogeneities. The dynamical evolution of the surface nanobubbles then follows from the diffusion equation, Laplace's equation, and Henry's law. In particular, one obtains stable surface nanobubbles when the gas influx from the gas-oversaturated water and the outflux due to Laplace pressure balance. This is only possible for small enough surface bubbles. It is therefore the gas or oil oversaturation ζ that determines the contact angle of the surface nanobubble or nanodroplet and not the Young equation. The review also covers the potential technological relevance of surface nanobubbles and nanodroplets, namely, in flotation, in (photo)catalysis and electrolysis, in nanomaterial engineering, for transport in and out of nanofluidic devices, and for plasmonic bubbles, vapor nanobubbles, and energy conversion. Also given is a discussion on surface nanobubbles and nanodroplets in a nutshell, including theoretical predictions resulting from it and future directions. Studying the nucleation, growth, and dissolution dynamics of surface nanobubbles and nanodroplets will shed new light on the problems of contact line pinning and contact angle hysteresis on the submicron scale. © 2015 American Physical Society. © 2015 American Physical Society.


Hohenberg P.C.,New York University | Krekhov A.P.,Max Planck Institute for Dynamics and Self-Organization
Physics Reports | Year: 2015

This paper presents an introduction to phase transitions and critical phenomena on the one hand, and nonequilibrium patterns on the other, using the Ginzburg-Landau theory as a unified language. In the first part, mean-field theory is presented, for both statics and dynamics, and its validity tested self-consistently. As is well known, the mean-field approximation breaks down below four spatial dimensions, where it can be replaced by a scaling phenomenology. The Ginzburg-Landau formalism can then be used to justify the phenomenological theory using the renormalization group, which elucidates the physical and mathematical mechanism for universality. In the second part of the paper it is shown how near pattern forming linear instabilities of dynamical systems, a formally similar Ginzburg-Landau theory can be derived for nonequilibrium macroscopic phenomena. The real and complex Ginzburg-Landau equations thus obtained yield nontrivial solutions of the original dynamical system, valid near the linear instability. Examples of such solutions are plane waves, defects such as dislocations or spirals, and states of temporal or spatiotemporal (extensive) chaos. © 2015 Elsevier B.V.


Martens E.A.,Max Planck Institute for Dynamics and Self-Organization
Chaos | Year: 2010

We study a network of three populations of coupled phase oscillators with identical frequencies. The populations interact nonlocally, in the sense that all oscillators are coupled to one another, but more weakly to those in neighboring populations than to those in their own population. Using this system as a model system, we discuss for the first time the influence of network topology on the existence of so-called chimera states. In this context, the network with three populations represents an interesting case because the populations may either be connected as a triangle, or as a chain, thereby representing the simplest discrete network of either a ring or a line segment of oscillator populations. We introduce a special parameter that allows us to study the effect of breaking the triangular network structure, and to vary the network symmetry continuously such that it becomes more and more chain-like. By showing that chimera states only exist for a bounded set of parameter values, we demonstrate that their existence depends strongly on the underlying network structures, and conclude that chimeras exist on networks with a chain-like character. © 2010 American Institute of Physics.


Hallatschek O.,Max Planck Institute for Dynamics and Self-Organization
PLoS Computational Biology | Year: 2011

Adaptation in spatially extended populations entails the propagation of evolutionary novelties across habitat ranges. Driven by natural selection, beneficial mutations sweep through the population in a "wave of advance". The standard model for these traveling waves, due to R. Fisher and A. Kolmogorov, plays an important role in many scientific areas besides evolution, such as ecology, epidemiology, chemical kinetics, and recently even in particle physics. Here, we extend the Fisher-Kolmogorov model to account for mutations that confer an increase in the density of the population, for instance as a result of an improved metabolic efficiency. We show that these mutations invade by the action of random genetic drift, even if the mutations are slightly deleterious. The ensuing class of noise-driven waves are characterized by a wave speed that decreases with increasing population sizes, contrary to conventional Fisher-Kolmogorov waves. When a trade-off exists between density and growth rate, an evolutionary optimal population density can be predicted. Our simulations and analytical results show that genetic drift in conjunction with spatial structure promotes the economical use of limited resources. The simplicity of our model, which lacks any complex interactions between individuals, suggests that noise-induced pattern formation may arise in many complex biological systems including evolution. © 2011 Oskar Hallatschek.


Monteforte M.,Max Planck Institute for Dynamics and Self-Organization
Physical Review Letters | Year: 2010

We demonstrate deterministic extensive chaos in the dynamics of large sparse networks of theta neurons in the balanced state. The analysis is based on numerically exact calculations of the full spectrum of Lyapunov exponents, the entropy production rate, and the attractor dimension. Extensive chaos is found in inhibitory networks and becomes more intense when an excitatory population is included. We find a strikingly high rate of entropy production that would limit information representation in cortical spike patterns to the immediate stimulus response. © 2010 The American Physical Society.


Herminghaus S.,Max Planck Institute for Dynamics and Self-Organization
Physical Review Letters | Year: 2012

The wetting properties of solid substrates with mesoscale (between van der Waals tails and the capillary length) random roughness are considered as a function of the microscopic contact angle of the wetting liquid and its partial pressure in the surrounding gas phase. It is shown that the well-known transition occurring at Wenzel's angle is accompanied by a transition line at which a jump in the adsorbed liquid volume occurs. This should be present generally on surfaces bearing homogeneous, isotropic random roughness. While a similar abrupt filling transition has been reported before for certain idealized groove or trough geometries, it is identified here as a universal phenomenon. Its location can be analytically calculated under certain mild conditions. © 2012 American Physical Society.


Avila M.,Max Planck Institute for Dynamics and Self-Organization | Avila M.,Friedrich - Alexander - University, Erlangen - Nuremberg
Physical Review Letters | Year: 2012

Turbulent transport of angular momentum is a necessary process to explain accretion in astrophysical disks. Although the hydrodynamic stability of disklike flows has been tested in experiments, results are contradictory and suggest either laminar or turbulent flow. Direct numerical simulations reported here show that currently investigated laboratory flows are hydrodynamically unstable and become turbulent at low Reynolds numbers. The underlying instabilities stem from the axial boundary conditions, affect the flow globally, and enhance angular-momentum transport. © 2012 American Physical Society.

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