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| ETH PHYSICS DEPARTMENT | ||
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COLLOQUIA WINTER SEMESTER 2002-2003 Wednesdays, 4:45pm, ROOM HPH-G4 Tea starts at 4:15pm ([AV]=Antrittsvorlesung) | ||
| Date | Title | Speaker |
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October 23 Host: R. Monnier | Complexity: hierarchical structure and scaling in Physics | R. Badii (Nortel-ZH) |
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November 6 Host: H-R. Ott | Order in Chaos: Magnetic Fields in the Life of a Star | M. Guedel (PSI Zurich) [AV] |
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November 13 Host: G. Dissertori | A precise measurement of the Muon Magnetic Anomaly as test of Standard Theory | K. Jungmann (Groningen) |
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November 15 - EXTRA!!! 11am, Room HPF-G6 Host: K. Ensslin | Molecules Cascades: Nanometer-Scale Structures that Compute | D. Eigler (IBM) |
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November 20 Host: H-R. Ott | Astrophysical Polarimetry: New perspectives for Planets, Stars and Active Galaxies | H-M. Schmid (ETH-Z) [AV] |
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November 27 Host: H-R. Ott | The Century of Space Science | M. Huber (ESA) |
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December 4 Host: G. Blatter | From high temperature superconductors to electrons in two dimension | T. Giamarchi (Geneva) |
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December 11 Host: T. Esslinger | Quantum computing and quantum communication with quantum optical systems | P. Zoller (Innsbruck) |
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December 18 Host: H-R. Ott | Dynamische Holographie und die Baendigung von Licht durch Licht | G. Montemezzani (ETH-Z) [AV] |
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January 8 Host: J. Osterwalder | Many-Body Physics in Cuprate Superconductors - Reports from Einstein's Electrons | Z.X. Shen (Stanford) |
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January 15 Host: M. Carollo | Heating Cooling Flows | J. Binney (Oxford) |
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January 22 Host: M. Carollo | From Molecules to Planets | E. van Dishoeck (Leiden) |
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January 29 Host: G. Dissertori | Physics Perspectives in the new Window for Gamma-Ray Astronomy between 20 and 350 GeV | E. Lorenz (Max Planck Munich) |
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February 5 Host: K. Ensslin | Zero Dimensional Fermi Liquid | B. Altshuler (Princeton) |
| Abstracts | ||
| November 6 | Order in Chaos: Magnetic Fields in the Life of a Star | M. Guedel |
| Magnetic fields play an important role in the formation and evolution of most stars in the Universe. They may emerge in unlikely places and at unexpected moments in a star's life to guide further evolution, or they may accompany stars throughout their lifetimes. This presentation will look back in time through the history of a star like the Sun, on which magnetic fields manifest themselves by heating a tenuous outer atmosphere and the solar wind to Millions of degrees. In younger stars, magnetic fields take control of braking the rapid stellar rotation due to a strong wind streaming along the field lines. The slower rotation, in turn, diminishes the high-energy radiation in X-rays and accelerated particles. In even earlier phases of stellar evolution, magnetic fields are thought to be in charge of accretion processes via an accretion disk, organizing not only the accumulation of mass onto the forming star, but probably also the removal of excess mass through the formation of jets. In the earliest phases, before a star is born, magnetic fields are probably once more of fundamental importance, this time guiding the contracting molecular cloud towards an orderly evolving protostar, against rapid gravitational collapse. The presentation will conclude by illustrating examples of other sources in the Universe where similar physics may be at work. | ||
| November 13 | A precise measurement of the Muon Magnetic Anomaly as Test of Standard Theory | K. Jungmann |
| At the Brookhaven National Laboratory a new measurement of the magnetic anomaly of the positive muon has been performed in a highly homogeneous magnetic^M storage ring by an international collaboration. This quantity is known now to 0.7 ppm. At such a level of precision this provides a sensitive test of calculations in the framework of Standard Theory. While an unambiguous discrepancy between experiment and theory could reveal the existence of potential contributions arising from physics beyond the Standard Model, eventual agreement would be highly important to limit parameters in a variety of speculative models. The experiment and its implications will be discussed. | ||
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November 15 EXTRA! 11am! | Molecules Cascades: Nanometer-Scale architectures that compute | D. Eigler |
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The scanning tunneling microscope (STM) can be used to build atomically-precise structures and investigate their physical and functional properties. I w
ill present a new class of nanometer-scale structures, "molecule cascades," that are both instructive -- they enable detailed studies of adsorbate motion
, and functional -- they do computation.
Carbon monoxide molecules were arranged in atomically-precise configurations in which the motion of one molecule causes the subsequent motion of another,
and so on in a cascade of motion similar to a row of toppling dominoes. Isotopically pure cascades were assembled on a Cu(111) surface using a low temp
erature STM. The hopping rate of CO molecules in cascades was found to be independent of temperature below 6K and exhibit a pronounced isotope effect, h
allmarks of a quantum tunneling process. At higher temperatures we observed a thermally-activated hopping rate with an anomalously low Arrhenius prefact
or that we interpret as tunneling from excited vibrational states. We present a cascade-based computation scheme which has all of the devices and interc
onnects required for the one-time computation of an arbitrary logic function. Logic gates and other devices were implemented by engineered arrangements
of molecules at the intersections of cascades. We demonstrate a 3-input sorter that uses several AND gates and OR gates, and the crossover and fan-out u
nits needed to connect them.
I will compare our circuits with CMOS technology and motivate why we are interested in implementing spin-based cascade computation in nanometer-scale str
uctures. Work done in collaboration with Christopher Lutz, Andreas Heinrich and Jay Gupta of the IBM Almaden Research Center |
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| November 20 | Astrophysical Polarimetry: New Perspectives for Planets, Stars and Active Galaxies | H-M. Schmid |
| In an introductory part important processes producing light polarization, like scattering and Zeeman effect, are recalled, and their potential for astrophysical research is discussed. As an example a description of a spectropolarimetric observing program of active galactic nuclei (quasars) with the ESO Very Large Telescope is given. Active galactic nuclei often show a strong linear polarization due to scattering and obscuration of the light from the bright core. Polarimetric measurements are essential for the investigation of these still badly understood objects. Further, a project of the Institute of Astronomy is presented for building a novel instrument for high precision polarimetry of bright targets. The new polarimeter has also been proposed as second generation instrument for the ESO Very Large Telescope for searching the reflected light from extra-solar planets. | ||
| November 27 | The Century of Space Science | M. Huber |
| In the course of its brilliant evolution through the 20th century, space science brought spectacular results and led to fundamental scientific findings. In the early quest for high altitude, in a balloon flight, Viktor Hess discovered cosmic rays in 1912. Following the Second World War, in 1946, sounding rockets were used to study the structure of the terrestrial atmosphere - the threshold of space. Sputnik 1, the first satellite, launched in 1957, sensed the near-Earth environment at orbital altitude and, in 1969, humans landed for the first time on an extraterrestrial body, the Moon. Today, sophisticated space probes explore distant worlds, and space telescopes look back in time towards the early Universe. We will tell the story of science in space and speak about its impact on today's science and the world we live in. | ||
| December 4 | From high temperature superconductors to electrons in two dimension | T. Giamarchi |
| With the discovery of high temperature superconductors, the practical challenge of obtaining compounds able to better transport current have led to re-open the pandora box of the very fundamental problem of the effect of disorder on crystals. Indeed crystals, though usually highly stable, are inordinately sensitive to external disorder. Even an infinitesimal amount of impurities leads to the destruction of the crystalline order. What is the resulting state of matter is a longstanding and highly debated issue. Disorder gives rise to properties analogous to those of glasses but with subtle differences, which certainly complicates the task of the theorist but lead to very exciting novel properties. The consequences of such a study reach way beyond the field of superconductors since the physics of such disordered elastic systems underlies many other different experimental situations such as magnets, ferroelectrics and even the electron gas inside a field effect transistor. | ||
| December 11 | Quantum computing and quantum communication with quantum optical systems | P. Zoller |
| We discuss theoretical aspects of implementation of quantum computers with quantum optics, and draw a connection with solid state physics. Quantum optics proposals typically assume that qubits are stored in longlived atomic states of single atoms. We discuss the underlying techniques of trapping and cooling of atoms. As a digression, we emphasize the role of the recently observed superfluid-Mott insulator transition of atoms as a loading technique for a large number of qubits in optical lattices, and the engineering of Hubbard type models with controllable parameters in atomic physics. Furthermore, we discuss in detail the realization of single and two-qubit gates with ions, atoms and in Cavity QED, and comment on the scalability of quantum optical proposals. We conclude our atomic physics part with a brief discussion of the role of atomic ensembles in quantum information processing. Finally, we outline the relation of quantum optics proposals to schemes for optical manipulation of quantum dots. The specific idea discussed is a spin based quantum computer with a charged (self assembled) quantum dots as qubits, and the implementation of fast one and two-qubit gates with short laser pulses. | ||
| December 18 | Dynamische Holographie und die Baendigung von Licht durch Licht | G. Montemezzani |
| Im freien Raum wechselwirken Lichtwellen nicht miteinander. In geeigneten Materialien hingegen verliert die Wellengleichung ihre Linearitaet, was zu verschiedenartigen, nichtlinearen-optischen Effekten fuehrt. Besonders interessant sind dabei solche Effekte, die bereits bei kleiner oder moderater Intensitaet der Lichtstrahlung (mW/cm2) auftreten, wie z.B. im Fall von konventionellen oder auch interband photorefraktiven Effekten. Diese sind indirekte, nichtlinear-optische Effekte, hervorgerufen durch Ladungsumverteilung, die das Aufnehmen dynamisch adaptierender Hologramme ermoeglichen. Der Vortrag wird zuerst die physikalischen Grundlagen solcher Effekte erlaeutern. Danach wird auf deren Verwendung in verschiedenen Bereichen eingegangen. Die resultierende Licht-Licht Wechselwirkung kann z. B. dazu benuetzt werden, um kohaerente Verstaerkung und holographische Interferometrie mit beliebigen Wellenfronten zu erzielen, um phasenkonjugierte Wellen durch einen selbstorganisierten Prozess zu erzeugen, oder um Information auf Lichtwellen parallel zu verarbeiten, wie z. B. in einem optischen Korrelator. Es wird auch gezeigt, wie ein Lichtstrahl den eigenen Wellenleiterkanal "graebt", was schliesslich zur Bildung eines optischen raeumlichen Solitons fuehren kann. Analog dazu koennen die Kanaele durch eine externe Beleuchtung dynamisch geschrieben werden, was die Steuerung und Schaltung von Licht durch Licht ermoeglicht. | ||
| January 8 | Many-Body Physics in Cuprate Superconductors - Reports from Einstein's Electrons | Z.X. Shen |
| Complex many-body process in solids is a major theme of modern physics. Truly deep insights of the process often have to come from sophisticated measurement techniques. Among such techniques, only angle-resolved photoemission spectroscopy reveals the direction, the speed, and the scattering mechanism of valence electrons. In the past decade, enormously improved resolution and experimental collaborations have elevated this technique from a band mapping tool to an important many-body spectroscopy. This talk reviews the important many-body processes in cuprate superconductors revealed by this technique: 1) well defined Fermi surface in overdoped metal; 2)d-wave structure of the superconducting gap; 3) pseudogap in the normal state of underdoped metal; 4) the emergence of coherent quasiparticle peak upon the superconducting transition; 5) the dynamics of a single hole in an antiferromanget; 6) the novel evolution of the electronic structure with doping, and 7) manifestations of the electron-lattice interaction. These findings have strongly influenced our thinking about these novel oxides. | ||
| January 15 | Heating Cooling Flows | J. Binney |
| The potential wells of massive galaxy clusters and elliptical galaxies are filled with X-ray emitting gas. In the majority of cases the cooling time at the centre is significantly less than the Hubble time. This phenomenon is clearly key for understanding galaxy formation. In the last two years data from XMM-Newton and Chandra have at last undermined confidence in the steady-state cooling-flow model that for two decades was the standard paradigm. The observational and theoretical case against the steady-state model will be presented and our current understanding of cooling flows as dynamical phenomena driven by AGN will be outlined. | ||
| January 22 | From Molecules to Planets | E. van Dishoeck |
| Stars and planetary systems are born deep inside molecular clouds of gas and dust. The detection of nearly 100 exo-solar planets around nearby stars shows that the formation of gas-rich giant planets is common. But how do these planets form? Although it is commonly accepted that they originate in the circumstellar disks around young stars, little is known about the physical and chemical processes in such regions. Only long wavelength observations are able to probe deep inside these stellar and planetary nurseries. In this talk, an overview will be given of recent developments in the area of star- and planet formation, with emphasis on the wealth of spectroscopic results. The evolution of the gas and dust from molecular clouds to protostars and forming planetary systems will be traced using recent examples from submillimeter and mid-infrared telescopes. The need for future high sensitivity, high angular resolution observations such as will be provided by the Atacama Large Millimeter Array and the James Webb Space telescope will be emphasized. | ||
| January 29 | Physics Perspectives in the new Window for Gamma-Ray Astronomy between 20 and 350 GeV | E. Lorenz |
| In 2003 a number of large diameter Air Cherenkov telescopes (CANGAROO, H.E.S.S., MAGIC, VERITAS) for very high energy gamma-ray astronomy will start to take data. These high sensitivity telescopes were designed for observations in the up to now inaccesseable energy range between 20-350 GeV where fundamental changes in gamma-ray emission from distant cosmic objects must occur. Prospects for observations and some of the astrophysics implications will be discussed. | ||
| February 5 | Zero Dimensional Fermi Liquid | B. Altshuler |
| The paradigm of Fermi liquid is in the focus of any theoretical description of normal metals. Although formally the interaction between the current curriers is not week -potential energy of the interaction usually exceeds the kinetic energy - many questions can be answered in terms of weakly interacting quasiparticles. At the same time there exist materials and physical situations for which the Fermi liquid approach is not applicable. Nevertheless we will not discuss possible "non-Fermi liquid" states and instead will revisit the foundations of the Fermi liquid theory. Traditional formulation of this theory is based on the translation invariance of the problem, which makes momenta of the quasiparticles good quantum numbers. Is it possible to discuss in a similar way situations, when the translation invariance is violated by a static potential (e.g., static disorder)? We will concentrate on the most dramatically different case - when electrons are confined in a rather small volume, and the relevant energy scales, such as temperature, are small. It turns out that such systems (quantum dots) can be described in a way that indeed resembles the Fermi liquid in all of its basic conclusions. We will illustrate the validity of this "Fermi droplet" theory by a number of examples. | ||
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Organized by: Marcella Carollo (marcella.carollo@phys.ethz.ch), Guenther Dissertori (guenther.dissertori@cern.ch) | ||
Back to the WS 2004-2005 ETH PHYSICS COLLOQUIA
| Last Update: 14 January 2003 | marcella.carollo@phys.ethz.ch |
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