E. Roldán, I. Neri, M. Dörpinghaus, H. Meyr and F. Jülicher
Phys. Rev. Lett. 115, 250602 (2015)
We show that the steady-state entropy production rate of a stochastic process is inversely proportional to the minimal time needed to decide on the direction of the arrow of time. Here we apply Wald’s sequential probability ratio test to optimally decide on the direction of time’s arrow in stationary Markov processes. Furthermore, the steady-state entropy production rate can be estimated using mean first-passage times of suitable physical variables. We derive a first-passage time fluctuation theorem which implies that the decision time distributions for correct and wrong decisions are equal. Our results are illustrated by numerical simulations of two simple examples of nonequilibrium processes.
Polarized Endosome Dynamics by Spindle Asymmetry During Asymmetric Cell Division
E. Derivery, C. Seum, A. Daeden, S. Loubéry, L. Holtzer, F. Jülicher and M. Gonzalez-Gaitan
Nature 528, 280 (2015)
During asymmetric division, fate determinants at the cell cortex segregate unequally into the two daughter cells. It has recently been shown that Sara (Smad anchor for receptor activation) signalling endosomes in the cytoplasm also segregate asymmetrically during asymmetric division. Biased dispatch of Sara endosomes mediates asymmetric Notch/Delta signalling during the asymmetric division of sensory organ precursors in Drosophila1. In flies, this has been generalized to stem cells in the gut and the central nervous system, and, in zebrafish, to neural precursors of the spinal cord. However, the mechanism of asymmetric endosome segregation is not understood. Here we show that the plus-end kinesin motor Klp98A targets Sara endosomes to the central spindle, where they move bidirectionally on an antiparallel array of microtubules. The microtubule depolymerizing kinesin Klp10A and its antagonist Patronin generate central spindle asymmetry. This asymmetric spindle, in turn, polarizes endosome motility, ultimately causing asymmetric endosome dispatch into one daughter cell. We demonstrate this mechanism by inverting the polarity of the central spindle by polar targeting of Patronin using nanobodies (single-domain antibodies). This spindle inversion targets the endosomes to the wrong cell. Our data uncover the molecular and physical mechanism by which organelles localized away from the cellular cortex can be dispatched asymmetrically during asymmetric division.
New research group 'Nonequilibrium Quantum Matter'
We welcome Prof. Takashi Oka who joined the institute from University of Tokyo to head the research group 'Nonequilibrium Quantum Matter'. The joint group between the our institute and the neighbouring MPI for Chemical Physics of Solids (MPI- CPfS) was established in order to provide an organisational framework combining the respective expertise of the institutes, in particular enabling a young scientist to benefit from both access to experimental work at MPI-CPfS and the theory environment at MPIPKS.
Max Planck Fellow Prof. Roland Ketzmerick extended until 2020
The Max Planck Fellow Programme promotes cooperation between outstanding university professors and Max Planck Society
researchers. The appointment of university professors as Max Planck Fellows is limited to a five-year period with the possibility of a five-year extension and entails the supervision of a small working group at a Max Planck institute.
We are very happy to announce that the Max Planck Fellow Group of Prof. Roland Ketzmerick (TU Dresden) has been extended by the Max Planck Society until 2020.
Max Planck Research Magazin features Jens Bardarson
What do soccer and quantum mechanics have in common? Both have surprising twists in store that are difficult to predict. Soccer, however, at least follows some rules that are more or less reliable. As a striker, Jens Hjörleifur Bárdarson controls the ball; as a physicist, he masters the rules of the quantum universe. The 35-year-old researcher at the Max Planck Institute for the Physics of Complex Systems in Dresden studies atomic particles, which display many a tricky move.
Many-Body Localization Characterized from a One-Particle Perspective
We show that the one-particle density matrix $\rho$ can be used to characterize the interaction-driven many-body localization transition in closed fermionic systems. The natural orbitals (the eigenstates of $\rho$ ) are localized in the many-body localized phase and spread out when one enters the delocalized phase, while the occupation spectrum (the set of eigenvalues of $\rho$ ) reveals the distinctive Fock-space structure of the many-body eigenstates, exhibiting a step-like discontinuity in the localized phase. The associated one-particle occupation entropy is small in the localized phase and large in the delocalized phase, with diverging fluctuations at the transition. We analyze the inverse participation ratio of the natural orbitals and find that it is independent of system size in the localized phase.
S. Bera, H. Schomerus, F. Heidrich-Meisner, and J. H. Bardarson
Phys. Rev. Lett. 115, 046603 (2015)
Avalanche outbreaks emerging in cooperative contagions
During human history the world has witnessed an immense loss of lives caused by infectious diseases. The number of casualties becomes even more concerning the cases of syndemic diseases (cooperative contagion), when two or more diseases co-infect individuals in a host population. For example the 1918 Spanish pandemic killed 20-40 million people mainly because of secondary bacterial infections. Contemporary syndemics that pose a major threat to public health include coinfection of HIV, Hepatitis B, C and TB. Here we modeled pathogens that spread and interact on networks, i.e. contact networks between individuals. These interactions can be cooperative and effectively change the way syndemic diseases spread and proliferate in populations. We showed that cooperation of the spreading infections can cause abrupt unexpected outbreaks at smaller epidemic thresholds, while underlying network can amplify or suppress this effect.
W. Cai, L. Chen, F. Ghanbarnejad, and P. Grassberger
Nature Physics (2015)
Johannes Knolle erhält den Dissertationspreis der Sektion kondensierte Materie der DPG
Ziel des Preises ist die Anerkennung herausragender wissenschaftlicher Arbeit und deren exzellenter Darstellung in einem Vortrag. Zur Verleihung an Johannes Knolle, der am MPIPKS in der Abteilung Kondensierte Materie promovierte, schreibt die Jury: Die numerisch exakte Evaluierung des dynamischen Strukturfaktors einer fraktionierten Quantenspinflüssigkeit stellt einen Durchbruch für unser Verständnis topologischer Magnete in zwei Dimensionen dar. Sie ist von Bedeutung für die Suche nach topologischen Materialien, für die Methodik der Vielteilchentheorie, sowie als Beispiel eines lokalen Quantenquenches.
Dr. Frank Pollmann erhält den Walter-Schottky-Preis 2014 für seine Arbeit zum Konzept symmetriegeschützter topologischer Zustände. Das Preiskomittee schreibt: In den letzten Jahren hat das Feld topologischer Quantenzustände weltweit eine rasante Entwicklung genommen. Durch wegweisende Arbeiten haben Frank Pollmann und Andreas Schnyder mit ihren Ko-Autoren maßgeblich dazu beigetragen, die Vielfalt topologischer Systeme und Phänomene zu erkennen und an Hand von Symmetrieüberlegungen zu systematisieren. Andreas Schnyder gelang die Klassifizierung topologischer Isolatoren, Supraleiter und Halbmetalle. Frank Pollmann hat das Konzept symmetriegeschützter topologischer Ordnung entwickelt.
New research group 'Ultrafast laser-matter interaction'
The new group is headed by Dr. Alexandra Landsman and studies the creation of ultrafast flashes of light and the interaction of this ultrafast light with matter using a variety of numerical and analytic methods, ranging from the solution of the Schrodinger equation to semi-classical approaches to techniques from nonlinear dynamical systems.