Graduate Students

Name	Discipline/Position	Phone	Office
Romach Yoav	Condensed Matter Physics	02 6584 811	Bergman Bldg.
Pollak Ori	Atomic, Molecular and Optical Physics	02 6585 129	Marks Bldg.
Pilnyak Yehuda	Atomic, Molecular and Optical Physics	02 6584 473	Marks Bldg.
Padnos Dan	Astrophysics and Relativity
Orbach Nir	Nonlinear	02 6586 718	Levin 14
Ohayon Ben	Nuclear Hadronic and Few-Body Physics	02 6585 868	Kaplun Bldg.
Nussbaum Tomer	Astrophysics and Relativity
Mintz Gad	Biophysics and Interdisciplinary Research	02 6586 753	Silberman 3-306
Metzker Lior	Biophysics and Interdisciplinary Research	02 6585 783	Popick Bldg.
Meirzada Idan

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Upcoming Events

Yesterday

astrolunch: Rahul Kumar (Princeton)
- Start time: 12:30pm
- End date: Tuesday, April 24th
- End time: 01:30pm
- TITLE: Microphysics of Astrophysical ShocksABSTRACT: Astrophysical explosions, such as supernovae and GRBs, produce a strong shock wave in the interstellar medium. These shocks are formed primarily due to scattering of the charged particles in a self-generated magnetic turbulence, which is produced via various plasma instabilities. The characteristics of these instabilities at the microphysical scales determine bulk properties of the plasma, such as total energy in electrons and the strength of the amplified magnetic field. The self-consistent plasma simulations and analytical models can greatly advance our quantitative understanding of these microphysical plasma processes. In this talk, I will first discuss a strong heating of the electrons at the relativistic shocks where the foreshock turbulence is primarily due to the Weibel instability. Then, I'll discuss the growth and evolution of the plasma instabilities operating at high-Mach number supernovae shocks.
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Nonlinear Physics Seminar: "Condensate, uctuations and symmetries|a tale of 2D turbulence"
- Start time: 02:00pm
- End date: Tuesday, April 24th
- End time: 03:30pm
- Lecturer: Anna Frishman
  Princeton Center for Theoretical Science, Princeton University
  
  Abstract:
  Earths jet streams, Jupiters Great Red Spot and its zonal winds are all examples of persistent large scale flows, whose dynamics is to a good approximation two-dimensional. These
  flows are also highly turbulent, and the interaction between the turbulence and these coherent structures remains poorly understood. Apart from its geophysical relevance, 2D turbulence is a rich and beautiful fundamental system|where turbulence takes a counter-intuitive role. Indeed, in 2D, energy is transferred to progressively larger scales, which can terminate in the self organization of the turbulence into a large scale coherent structure, a so called condensate, on top of small scale fluctuations.
  I will describe a recent theoretical framework in which the profile of this coherent mean flow can be obtained, along with the mean momentum flux of the fluctuations. I will explain how
  and when the relation between the two can be deduced from dimensional analysis and symmetry
  considerations, and how it can be derived. Finally, I will show that, to leading order, the velocity
  two-point correlation function solves a scale invariant advection equation. The solution determines the average energy of the fluctuations, but does not contribute at this order to the momentum flux, due to parity + time reversal symmetry. Using analytic expressions for the solutions, matched to data from extensive numerical simulations, it is then possible to determine the main characteristics of the average energy. This is the first-ever self-consistent theory of turbulence-flow interaction.
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Today

Nonlinear Physics Seminar: "Membrane curvature and tension control the formation and collapse of caveolar superstructures"
- Start time: 12:00pm
- End date: Wednesday, April 25th
- End time: 01:30pm
- Lecturer: Michael Kozlov, Joseph Klafter Chair in Biophysics, Dept. of Physiology and Pharmacology Sackler Faculty of Medicine, Tel Aviv UniversityAbstract: Caveolae,the flask-shaped pits covered by caveolin-cavin coats, are abundant features ofthe plasma membrane of many cells. Besides appearing as single membraneindentations, caveolae are organized as superstructures in the form ofrosette-like clusters, whose mechanism of assembly and biological functionshave been elusive. Here we propose that clustering of caveolae is driven byforces originating from the elastic energy of membrane bending deformations andmembrane tension. We substantiate this mechanism by computational modeling,which recovers the unique shapes observed for the most ubiquitous caveolarclusters. We support the agreement between the calculated and observedconfigurations by electron tomography of caveolar clusters. The model predicts,quantitatively, the experimentally assessable dependences of caveolarclustering on membrane tension and on the degree of polymerization of thecaveolin-cavin coats. We propose that the role played by large caveolarclusters in cells is to substantially reinforce the mechano-protective functionof caveolae.
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Tomorrow

Condensed-Matter Physics Seminar: "Sticking, power laws and scaling statistics in the landscape of Hamiltonian phase space."
- Start time: 12:00pm
- End date: Thursday, April 26th
- End time: 01:30pm
- Lecturer: Or Alus
  Abstract:
  
  In typical Hamiltonian systems which model physical systems phase space dynamics is mixed, in some part of phase space the it is chaotic while in other parts it is regular. For systems with two degrees of freedom, and for periodically kicked systems with one degree of freedom, transport in the chaotic regions of phase space is dominated by sticking to complicated structures. The probability to stay in the vicinity of the initial point is a power law in time with a universal exponent for a wide class of systems. Statistical description of the transport is discussed. The description is based on scaling of different measures in phase space related to periodic and quasi periodic orbits' frequencies. This description is used in order to calculate the sticking time exponent in the framework of the Markov Tree model proposed by Meiss and Ott in 1986. Even though many approximations are used, it predicts important results quantitatively and with agreement to direct simulations. Quantum manifestation of this phenomenon and its relevance to time correlations is discussed as well, showing different behavior for increasing Planck's constant.
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Monday, April 30th

Physics Colloquium: "Access-to-Error"
- Start time: 12:00pm
- End date: Monday, April 30th
- End time: 01:30pm
- Lecturer: Dr. Michal Shur-Ofry, The Faculty of Law, The Hebrew University of Jerusalem
  Abstract:
  Access to knowledge is a crucial part of the innovation paradigm, and its significance for development and progress is well recognized. Conversely, the role of errors, failures, and additional types of negative information in the dynamics of innovation is insufficiently explored in law and policy scholarship. This Article focuses on errors as drivers of innovation, and explores new ways for facilitating access to error.
  
  Drawing on multidisciplinary research—ranging from philosophical accounts of progress, through studies of complex systems to accumulating reflections from diverse scientific communities—this Article demonstrates that, counterintuitively, errors and innovation are inextricably linked. Yet, the principal legal, institutional and social structures that regularly incentivize the diffusion of knowledge discourage, rather than encourage, the diffusion of errors. Intellectual property law, the primary mechanism for stimulating the dissemination of knowledge goods, is inherently limited in its ability to promote the dissemination of negative knowledge. The scientific establishment—whose reputational rewards and institutional funding schemes complement and sometimes substitute intellectual property incentives—offers no equal rewards when it comes to negative findings or falsifications. The result is insufficient access to negative knowledge, with acute and proven harms for innovation and progress.
  
  Against this analysis, this Article frames “access-to-error" as a pressing goal for innovation law and policy. It proposes a preliminary typology of negative information, and explores concrete policy measures to support an access-to-error paradigm, which correspond to the different types of errors. The proposals concentrate on three possible mechanisms: adjustments to the intellectual property regime, top-down regulation, and a state-supported commons-based approach.
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Tuesday, May 1st

Astrolunch: John Kirk (Max Planck Institute for nuclear physics)
- Start time: 12:30pm
- End date: Tuesday, May 1st
- End time: 01:30pm
- Gamma-ray flares from pulsar wind nebulae
  
  The flares of ∼ 400 MeV gamma-rays observed from the Crab Nebula by the AGILE and Fermi satellites pose a major challenge to theories of particle acceleration, since they (i) substantially exceed the astrophysical “upper limit” of ∼ mec2/αf on synchrotron radiation, (ii) vary on the time scale of hours, although they are likely to occur in the > .1pc-sized Nebula, and (iii) can reach up to 10% of the power of the entire Nebula. Many acceleration scenarios have been proposed to accommodate these properties, generally involving magnetic reconnection, Doppler boosting and/or “magneto-luminescence”. I will describe a new theory that does not straightforwardly fit into any of these categories: inductive acceleration in the pulsar wind. In it, gamma-ray flares result from a sudden drop in the mass-loading of the wind, which causes charge starvation; the current required to maintain wave activity is then carried by very few particles, which are inductively accelerated in the radial direction and reach very high Lorentz factors before encountering the termination shock. On impacting the Nebula, these particles produce a tightly beamed, high luminosity burst of hard gamma-rays, with properties strikingly similar to those observed. I will discuss the predictions of this theory and the prospects for checking them, including the possibility of detecting similar flares from other objects.
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