Physics of Complex Systems


Gregory Falkovich, Head

Elisha Moses is an experimentalist studying Neuro-Physics:
We are interested in experimental investigation of physical aspects in the brain. At present we are pursing three main directions.
Information flow. We construct living linear neural networks under our microscope that allow us to follow precisely the propagation of information along a biological Shannon-like information channel. Both one-dimensional and two-dimensional hippocampal cultures are studied using both optical and electric detection. Using a novel application of percolation theory, we obtain quantitative biological information about the connectivity of the living neural network.
Interaction of neurons with electromagnetism. We stimulate neurons using a non-invasive method, both in human brains and in cultured dishes, by applying a strong and short magnetic pulse. Applications to synchrony in the brain and the study of aspects of Schizophrenia offer a fascinating perspective.

Joel Stavans' group is currently engaged in studies of the interaction of proteins and DNA using single-molecule techniques, and the behavior of genetic networks in bacterial cells. Research on protein-DNA interactions is currently focused on the properties of homologous recombination. These studies are conducted using a variety of fluorescence techniques including fluorescence resonance energy transfer (FRET), and fluorescence correlation spectroscopy (FCS) at the ensemble and single-pair level. The group is also characterizing and modelling the properties of the dynamical response of small genetic networks in bacterial cells, in both large populations and single cells. Experiments are currently being carried out on (a) the SOS response, elicited as a result of genome damage and (b) small RNA-controlled networks.

Victor Steinberg's group is studying dynamics of various single flexible micro-objects and hydrodynamics of their solutions and suspensions. This year the following projects were under investigation: (i) Properties of elastic turbulence and mixing in polymer solutions for polymer concentrations from dilute till concentrated regimes; (ii) Single polymer dynamics and conformations in elastic turbulence and molecular stress sensor; (iii) Convective turbulence in SF6 near its gas-liquid critical point; (iv) Turbulent drag reduction in swirling flow due to addition of polymers; (v) Dynamics of a vesicle in shear, mixed and elongation flows (vi)Hydrodynamics and rheology of vesicle suspension; (vii) Development of technology of uniform size vesicles production.

Eytan Domany's research turned in the last years towards problems in Biology and Bioinformatics, with emphasis on development and application of methods for the visualization and analysis of data from high thoughput experiments. Computers play a central role in nearly all aspects of the group's work. Clustering, sorting and a variety of other statistical methods are used to study biological data - in particular, expression profiles obtained from DNA microarrays. We collaborate with several Weizmann research groups from the Life Sciences, as well as with laboratories at other Israeli institutions and hospitals, and also with groups from the US, Switzerland, France, Italy and Singapore on analysis of their gene expression data. Our main focus is on cancer, but we are open to other problem areas as well. Our activities range from rigorous mathematical work, through searching for binding sites of transcription factors, development of novel tools and their algorithmic implementation, to their application to analyze data obtained by our collaborating labs. A certain level of activity in Statistical Mechanics is maintained; for example, the structure of the low temperature phase of short-range spin glasses and properties of Hidden Markov processes are among the topics studied.

Gregory Falkovich studies systems far from equilibrium, in particular, turbulence. His main interest on a fundamental side is in symmetries. He studies anomalies i.e. breakdown of symmetries that do not disappear when symmetry-breaking factor goes to zero. With collaborators in France and Italy, he discovered new emerging symmetries like conformal invariance in inverse turbulent cascades and now tries to incorporate this in turbulence theory. He also studies spectral condensates that appear in inverse cascades and condensate-turbulence interaction. On a practical side he is working on the quantitative theory of rain initiation in turbulent warm clouds and on the way large-scale coherent flows (condensates) affect turbulence.

David Mukamel's group is active in the general area of statistical physics. In particular extensive studies of collective phenomena far from thermal equilibrium have been carried out. Models corresponding to phase separation, wetting and roughening transitions, and coarsening processes have been introduced and studied. Equilibrium collective phenomena are also investigated in various contexts. The denaturation and unzipping phase transitions of DNA molecules have been analyzed. Peculiar phenomena which are characteristic of systems with long range interactions (such as gravitational systems) have also been investigated.

In Uzy Smilansky's group, research on Quantum Chaos evolves around the following topics: Quantum graphs - spectral statistics, scattering and trace formulae. The morphology of nodal lines of billiards wave functions and the number of nodal domains are investigated, with two aims: To establish a criterion of quantum chaos, and to determine the extent by which knowledge of the nodal set determines the billiard shape. We have still some interest in the following subjects: Conditions for hyperbolicity for billiards on surfaces with constant curvatures. Quantization of billiards in homogeneous magnetic fields, and the density of exterior and interior edge states. The classical and quantum spectral duality.

Nir Davidson's group develops new techniques for laser cooling and trapping of neutral atoms. They are studying new optical traps that are based on repulsive light forces, in which spontaneous emission of photons is suppressed. Such traps provide long atomic coherence times and hence enable extremely accurate spectroscopic and dynamical measurements, including observation of chaotic motion of ultra-cold atoms in optical "billiards". They are also conducting experiments in a Bose-Einstein condensate including measurements of its zero-temperature excitation spectra its ground state properties and its coherence.

Asher A. Friesem and his group are conducting basic investigations on non-conventional elements based on diffractive and planar optics, on the resonance behavior of grating-waveguide structures, on the performance of special phase elements inside laser cavities, and on new optical architectures for a variety of applications. These investigations are leading to new laser configurations, highly advanced optical arrangements for displays, high-speed electro-optic devices and special biological and chemical sensors.

Yaron Silberberg and his group are studying ultrafast and nonlinear optics. Using femtosecond optical pulses, they study how the shape of these pulses affects the interaction between the light and atoms or molecules. In particular, the group investigates how shaped pulses can be used in nonlinear laser spectroscopy. Shaping also affect nonclassical sources of light, and shaping of single photon sources has been demonstrated. In another effort, the group investigates nonlinear microscopy - using femtosecond pulses in biological microscopy. The group has developed a new type of microscope based on third-harmonic generation and it tests it on various types of biological specimens. Finally, the group also works on soliton physics, and continues its studies of discrete solitons in waveguide arrays.

Adam Schwimmer continued to study various aspects of Quantum Field Theory and String theory and their interrelation. In particular the group studied the relation between Conformal Field Theories appearing on the boundary of AdS type space-times and the String Theory description in the bulk. The role played by the stringy Solitons ("D-branes") in holographic theories was elucidated.

Tsvi Tlusty and his group deal with modeling living information systems, their molecular components and the way they evolve. A central question in this field is the impact of the inherent molecular recognition noise on the design of information channels. We examine this question in the contexts of the genetic code and the transcription regulatory network (with Uri Alon). A specific example that is currently considered is the circuitry that controls the p53 tumor-suppressor (with Tzachi Pilpel). On a more microscopic scale, we examine the actual physical forces that act during molecular recognition and suggest that the structure of certain bio-recognizers has evolved to optimize the quality of detection. The suggested design principles are considered as possible engines that could drive the evolution of biological information systems. Other research activities include modeling 2D neural networks in terms of percolating random graphs (with Elisha Moses) and the theory of particle-laden microfluidic flow (with Roy Bar-Ziv).

Dan Oron and his group are studying nonlinear dynamics in nanocrystals using ultrafast time-resolved techniques as well as quasi-continuous-wave energy- and frequency- resolved methods. Much of the research effort is aimed towards utilizing the unique resonant properties of semiconducting and metallic nanoparticles towards applications as nonbleaching contrast agents in bioimaging. The group also studies the fundamental aspects of exciton-exciton interactions in multicomponent semiconductor quantum dots and in doped quantum dots. In this context, possible applications in optical gain devices and in photovoltaics are explored.

Roee Ozeri's group uses laser cooled and trapped ions for quantum information, quantum optics and quantum metrology experimental studies. In particular we focus on the quantum information aspects of ion-photon interactions. The coupling of an ion-qubit to the elecro-magnetic vacuum through spontaneous photon scattering is studied as a generic model for quantum noise. The decoherence induced as well as active methods to correct for it through quantum feedback are explored.

Nirit Dudovich's group studies basic phenomena in strong field light-matter interactions. In particular, the group focuses on the generation and measurement of attoseconds pulses (1 attosecond is 10-18 seconds). The advent of time resolved measurements with attosecond resolution opens new fields in which the observation of fast electronic dynamics can be attained. The group develops new approaches to observe highly nonlinear interactions and to manipulate their evolution in time and space.

http://www.weizmann.ac.il/complex/

Research Staff, Visitors and Students

Professors

Nir Davidson, Ph.D., Weizmann Institute of Science, Rehovot, Israel
       The Peter and Carola Kleeman Professor of Optical Sciences
Eytan Domany, Ph.D., Cornell University, Ithaca, United States
       The Henry J. Leir Professorial Professor
Gregory Falkovich, Ph.D., Novosibirsk State University
Elisha Moses, Ph.D., Weizmann Institute of Science, Rehovot, Israel
David Mukamel, Ph.D., Weizmann Institute of Science, Rehovot, Israel
       The Harold J. and Marion F. Green Professor
Yaron Silberberg, Ph.D., Weizmann Institute of Science, Rehovot, Israel
       The Harry Weinrebe Professor of Laser Physics
Uzy Smilansky, Ph.D., Weizmann Institute of Science, Rehovot, Israel (on extension of service)
       The Wolfgang Gentner Professor of Nuclear Physics
Joel Stavans, Ph.D., University of Chicago, United States
Victor Steinberg, Ph.D., Laboratory of Critical Phenomena, Moscow, Russian Federation (on extension of service)
       The Harry de Jur Professor of Applied Physics

Professors Emeriti

Asher Friesem, Ph.D., University of Michigan, Ann Arbor, United States
Adam Schwimmer, Ph.D., Weizmann Institute of Science, Rehovot, Israel

Senior Scientists

Nirit Dudovich, Ph.D., Weizmann Institute of Science, Rehovot, Israel
       Yigal Allon Fellow
Dan Oron, Ph.D., Weizmann Institute of Science, Rehovot, Israel
       Yigal Allon Fellow
Roee Ozeri, Ph.D., Weizmann Institute of Science, Rehovot, Israel
Tsvi Tlusty, Ph.D., Weizmann Institute of Science, Rehovot, Israel
      Center for Complexity Science Fellowship

Engineers

Rostyslav Baron, Ph.D., Institute of Low Temperatures, Kharkov's, Russian Federation
Yuri Burnishev, Ph.D., Ural Branch of the USSR Academy of Science, Russian Federation

Consultants

Rakos Attila (left April 2008)
Ittai Fattal, Belinson Hospital, Petach-Tikva, Israel
Itzhak Fouxon, Tel Aviv University, Tel-Aviv, Israel
Asher Friesem
Michael Golub, ExPlay Ltd., Herzliya, Israel (left April 2008)
Nissan Itzhaki, Tel Aviv University, Tel-Aviv, Israel
Yariv Kafri, Technion - Israel Institute of Technology, Haifa, Israel
Ido Kanter, Bar-Ilan University, Ramat-Gan, Israel
Nava Levit Binnun, Interdisciplinary Center (IDC), Herzliya
Eliezer Rabinovici, The Hebrew University of Jerusalem, Jerusalem, Israel
Shahar Seifer, Independent
Noam Shental, The Open University, Raanana, Israel
Shmuel Starobinets
Shimon Yankielowicz, Tel Aviv University, Tel-Aviv, Israel
Norman Zabusky, Rutgers University, NJ., USA
Or Zuk, MIT, Harvard, USA

Visiting Scientists

Michael Aizenman, Princeton University , NJ, U.S.A.
Abraham Beltzer, Holon Inst. of Technology, Israel
David Biron, University of Chicago, Il, U.S.A.
Raphael Chetrite, Ecole Normale Superiuer de Lyon, France
Julien Deschamps, University of Marseille Provence, France
Jean-Pierre Eckmann, University of Geneva, Switzerland
Vasiliy Kadtsler, University of California at San Diego, CA, U.S.A.
Vasiliy Kantsler, University of California at San Diego, CA, U.S.A.
David Kutasov, University of Chicago, Il, U.S.A.
P.K. Mohanty, Tata Inst. of Fund. Rese. Mumbai, India
Roberto Morandotti, University of Quebec, Varennes, Canada
Gunter Schutz, HLRZ, Julich, Germany
Ilan Sharon, Hebrew University , Mount Scopus, Jerusalem, Israel
Jordi Soriano-Fradera, University of Postdam, Germany
Norman Zabusky, Rutgers University , NJ, U.S.A.

Postdoctoral Fellows

David Ben-Shlomo, Ph.D., Hebrew University of Jerusalem, Israel
Dipankar Bhattacharyya, University of Calcutta
Barry Dov Bruner, Ph.D., University of Toronto
Choeng Ryul Choi, Kyunghee University
Julien Samuel Kevin Deschamps, Ph.D., IRPHE
Adi Diner, Ph.D., Weizmann Institute of Science, Israel
David Jacques Gachet, Ph.D., Fresnel Institute, Aix-Marseille III university
Nicolas Alexandre Be Galle, University of LILLE 1
Leore Grosman, Ph.D., Hebrew University of Jerusalem, Israel
Shamik Gupta, Tata Institute of Fundamental Research
Yair Horesh, Ph.D., Bar-Ilan University, Israel
Shimshon Jacobi, Weizmann Institute of Science, Israel
Yonggun Jun, University of Pittsburgh
Vasiliy Kantsler, Ph.D., Weizmann Institute of Science, Israel
Nava Levit-Binnun, Weizmann Institute of Science, Israel
Yonggang Liu, Ph.D., Chinese Academy of Sciences
Madhavan Unni Perincherry Kulappar, Ph.D., Indian Institute of Science
Vaibhav Shridhar Prabhudesai, Ph.D., Tata Institute of Fundamental Research
Maria Rodriguez Martinez, Ph.D., Institut d'Astrophysique de Paris
Assaf Rotem, Ph.D., Weizmann Institute of Science, Israel
Tal Shay, Weizmann Institute of Science, Israel
Yair Shokef, Technion, Israel
Sanjiv Kumar Tiwari, Ph.D., Indian Institute of Technology Kanpur India

Research Students

Itai Afek Nitzan Akerman
Amnon Amir Amit Aronovitch
Assaf Avidan Ram Band
Nir Bar-Gill Yaron Bromberg
Zvicka Deutsch Yotam Drier
Vardit Eckhouse Yehonatan Elon
Moti Fridman Hilah Gal
Yinnon Glickman Tzahi Itzhak Grunzweig
Shimshon Jacobi Vasiliy Kantsler
Tsvi Katchalski Ori Katz
Shlomi Kotler Yoav Lahini
Adam Lampert Adina Lederhendler
Adam Mani Adi Natan
Shiri Nitzan- Meshner Idan Oren
Rami Pugatch Oren Raz
Assaf Rotem Eitan E. Rowen
Yoav Sagi Yonatan Savir
Dror Shafir Tal Shay
Michal Sheffer Haim Suchowski
Marija Vucelja Amit Zeisel

Administrator

Israel Gonen