|Jan. 25, 2005
||R.J. Dwayne Miller,
University of Toronto
Electron Diffraction: Atomic Level Movies
|Feb. 1, 2005
||Jack Hehn, American
Institute of Physics
||SPIN Up: A
Report from the National Task Force on Undergraduate Physics
The National Task Force on Undergraduate Physics (NTFUP) has recently published a report entitled “Strategic Programs for Innovation in Undergraduate Physics (SpinUP)” offering findings about and examples of Physics Departments that have shown success in increasing physics majors and student participation. The full report can be found at http://www.aapt.org/Projects/ntfup.cfm. This talk will review some of the most important findings from SpinUP and open questions about how your department might use these findings in its best interest. The work of NTFUP was supported by the ExxonMobil Foundation, the American Association of Physics Teachers (AAPT), the American Physical Society (APS), and the American Institute of Physics (AIP).
|Feb. 8, 2005
of optical singularities: a long and unfinished symphony
Simons lecturer. Metcalf and Abanov host.
|Feb. 15, 2005
||Eun-Suk Seo, University of Maryland||Space
Based Cosmic Ray Astrophysics Experiments
Cosmic rays, energetic particles coming from outer space, bring us information about the physical processes that accelerate particles to relativistic energies, about the effects of those particles in driving dynamical processes in our Galaxy, and about the distribution of matter and fields in interstellar space. The energy of these cosmic beams far exceeds energies produced by particle accelerators on Earth. Balloon-borne and space experiments are currently being used for understanding cosmic ray origin, acceleration and propagation, exploring the supernova acceleration limit, and searching for exotic sources such as dark matter and antimatter. Our on-going effort at Maryland with Balloon-borne Experiment with a Superconducting solenoid Spectrometer (BESS), Advanced Thin Ionization Calorimeter (ATIC), Cosmic Ray Energetics And Mass (CREAM), and Alpha Magnet Spectrometer (AMS) will be presented and challenges of extending precision measurements to highest energy practical will be discussed.
|Feb. 22, 2005
||Abhay Deshpande, Stony Brook||1/2 + 1/2 + 1/2 = 1/10???...
Learning the nucleon spin algebra using RHIC
|March 1, 2005
||Markus Buttiker, Geneva
Noise: From Schottky to Bell
Noise properties of small coherent electrical conductors have been at the forefront of research in mesoscopic physics for the past two decades. Most of the effort has been devoted to compare shot noise (suppression or enhancement) relative to Schottky's result for Poissonian shot noise. I discuss proposals to use shot noise correlations to extract entanglement information tested with the help of a Bell inequality. Of particular interest is orbital (instead of spin) entanglement generated by two-particle sources (emission of Cooper pairs, spontaneous or dynamically generated electron-hole pairs).
|March 8, 2005
||Scientific Challenges in Sustainable Energy Technology|
|March 15, 2005
George Sterman, Stony Brook YITP
Freedom: Then and Now
Asymptotic freedom is an essential property of quantum chromodynamics (QCD), the theory of the strong interactions. The discovery of asymptotic freedom was a landmark of modern particle physics and quantum field theory, recognized by the most recent Nobel Prize in physics. I will review some of the puzzles solved by QCD and asymptotic freedom, and continue with selected highlights from their continuing theoretical development and experimental explorations at high energy.
|March 29, 2005
||Carl Bender, Washington
Making Sense of Non-Hermitian Hamiltonians
The Hamiltonian H specifies the energy levels and the time evolution of a quantum theory. It is an axiom of quantum mechanics that H be Hermitian because Hermiticity guarantees that the energy spectrum is real and that the time evolution is unitary (probability preserving). In this talk we investigate an alternative formulation of quantum mechanics in which the conventional requirement of Hermiticity (transpose+complex conjugate) is replaced by the more physically transparent condition of space-time reflection (PT ) symmetry. We show that if the PT symmetry of a Hamiltonian H is not broken, then the spectrum of H is real. Examples of PT-symmetric non-Hermitian quantum-mechanical Hamiltonians are H=p2+ix3 and H = p2-x4. Amazingly, the energy levels of these Hamiltonians are all real and positive! The crucial question is whether PT -symmetric Hamiltonians specify physically acceptable quantum theories in which the norms of states are positive and the time evolution is unitary. The answer is that a Hamiltonian that has an unbroken PT symmetry also possesses a physical symmetry that we call C. Using C, we show how to construct an inner product whose associated norm is positive definite. The result is a new class of fully consistent complex quantum theories. Observables are defined, probabilities are positive, and the dynamics is governed by unitary time evolution. Many examples of PT -symmetric quantum mechanical and quantum field theoretic Hamiltonians will be discussed.
|April 5, 2005
||Ben Oppenheimer, American Museum of Natural History||The
Lyot Project: Toward Exoplanet Imaging and Spectroscopy
For the first time in history, scientists can image the environments of nearby stars on scales approaching that of our solar system. New classes of astrophysical objects have been discovered including circumstellar debris disks, and brown dwarfs. This heralds a new era of research into comparative exoplanetary science. The Lyot Project is a multifaceted research and development program based at the American Museum of Natural History. The project is designed to advance the techniques and science required for exoplanetary science, with a particular emphasis on the combination of adaptive optics and coronagraphy. The Lyot Project's initial goal has now been achieved: the construction, deployment and use of the world's first coronagraph optimized for, and operating at, the diffraction limit of a telescope. We are surveying the brighest, nearest stars with sensitivity to circumstellar debris disks and planets as small as a few jupiter masses.
|April 12, 2005
||Clare Grey, Stony Brook Chemistry||NMR
studies of structure and motion in fuel cell materials, batteries and
Our work in this field has focused on the development and application of the local probe of structure, NMR, to correlate structure with electrochemistry (for batteries), dynamics (fuel cells and oxygen separation membranes) and sorption properties (sequestration of environmentally-relevant ions on soil minerals). For example, 6Li MAS NMR has been used to study local electronic structures and Li local environments in layered cathode materials such as Li[M’xM1-x]O2 (M,M’ = Mn, Ni, Co etc.). We first developed a fundamental understanding of the causes of the large (hyperfine) NMR shifts typically observed in these paramagnetic samples. This knowledge was then applied to follow structural changes after charging and discharging of a battery, to help establish why some materials function well as electrode materials and others fail. These approaches may also be used to follow sorption processes on the iron oxyhydroxides that a present in large quantities in soils, systems that are generally considered very difficult to study by NMR. Finally, 17O MAS NMR spectroscopy has been employed to study dynamics in a series of ionic conductors. Since the individual oxygen-ion sites may be resolved with high-resolution NMR methods, we can now use a combination of one- and two-dimensional NMR methods to observe the mobile sites directly and to propose mechanisms for anion conduction.
|April 19, 2005
Goldhaber-Gordon, Stanford University
in Semiconductor Nanostructures
Electrons behave in remarkable ways when confined to fewer than three dimensions. Take for example a quantum point contact: a narrow constriction between two electron reservoirs, often thought of as a short 1-dimensional wire. The width of the constriction can be tuned so as to pass zero, one, two, or more channels of electrons, each with a quantized conductance of 2e2/h (around 80 µSiemens). As a point contact is just being opened up, its conductance pauses around 0.7 times 2e2/h, before rising to the first full-channel plateau. This "0.7 plateau" has been a prominent puzzle since 1994. I will discuss some recent experiments on quantum point contacts which shed light on the spin-related origin of this phenomenon. In the later part of my talk, I will explain some of the other interesting ways in which electron spin influences transport in semiconductor nanostructures.
|April 26, 2005
||Peter Goldreich, Institute for Advanced Study, Princeton; and Caltech||Final
Stages of Planet Formation
My talk will address three questions regarding solar system planets. What determined their number? Why are their orbits nearly circular and coplanar? How long did they take to form?
|May 3, 2005
Fall 2004 colloquia:
|Sep. 14, 2004
||Paul Grannis, Stony Brook Physics||Chairman's
colloquium: a survey
of the department
|Sep. 21, 2004
(Wang Center Theater, 4 pm)
University of Illinois
from Molecules to Man and Back
The first images using nuclear magnetic resonance were acquired by Dr. Paul Lauterbur at Stony Brook thirty years ago, and this achievement was recognized with the 2003 Nobel Prize in Medicine. His apparatus sits in the lobby of the Chemistry building. This Presidential lecture will recount his achievement (Wang Center Theater, 4 pm).
|Sep. 28, 2004 (the usual Tuesday 4:15 pm)
||Jin Wang, Stony Brook Chemstry||Biomolecular
Folding and Recognition-Energy Landscape Perspectives
I will give a review on the study of biomolecular folding and recognition. I will first discuss the energy landscape, establish the thermodynamics and identify the corresponding phase diagrams. I will then derive an optimization criterion for folding and recognition. I will also study the kinetics of folding and recognition. I will also connect the theory with the experiments.
|Sep. 30, 2004 (Thursday, 3:45 pm, Harriman 137)
||Carolyn Porco, Space Science
Institute, Boulder, CO
Rings of Saturn as Seen by Cassini
A special colloquium by the head of the Cassini imaging team, who is a former Stony Brook undergraduate. Dr. Porco will also give a talk aimed more at the general public in connection with homecoming, on Friday, Oct. 1 at 5 pm in the Wang Center.
|Oct. 5, 2004
|| Christopher Homes,
Scaling in High Temperature Superconductors
Superconductors, materials that have no resistance to the flow of electricity, have proven to be one of the great challenges in condensed matter physics. First discovered in 1911 at low temperature, it was not until almost 50 years had passed that a convincing theory was proposed to explain the phenomena. The area was considered be a mature field with few surprises left until the sudden and unexpected discovery in 1986 of superconductivity in copper-oxide materials at high temperatures (ultimately, well above liquid nitrogen); the mechanism of superconductivity in these materials is different than in conventional metals and alloys. Despite 18 years of intensive study, the nature of the super-conductivity in these systems is still not understood. Scaling laws express a systematic and universal simplicity among complex systems in nature. We have recently observed a linear scaling relation in the high-temperature superconductors between the strength of the superconducting condensate (a measure of the number of carriers in the superconducting state), the critical temperature, and the dc conductivity just above the critical temperature – this scaling relation does not depend on the crystal structure or direction. The concepts of superconductivity in metals will be reviewed, and the significance of this scaling law in the high-temperature superconductors will be explored.As discussed in a commentary and a recent paper in Nature (July 29, 2004)
|Oct. 12, 2004
||Rajiv Kamilla, Goldman Sachs||A
Physicist in Phynance: Structured Products
Adventures in finance by a recent Stony Brook Physics PhD.
|Oct. 19, 2004
||James Misewich, BNL Materials
of nanoscale systems
Carbon nanotubes have been shown to possess an astonishing array of interesting electrical and mechanical properties that could have significant technological impact (1,2). Recent progress includes a demonstration that carbon nanotubes can also be used to make a nanoscale current driven optical source (3). The interesting physics of this new optical source will be discussed.
(1) M.S. Dresselhaus, G. Dresselhaus, and Ph. Avouris (eds.), "Carbon Nanotubes", Topics Appl. Phys. 80, (2001).
(2) Ph. Avouris, Acct. Chem. Res. 35, 1026 (2002).
(3) J.A. Misewich, R. Martel, Ph. Avouris, J. Tsang, S. Heinze, and J. Tersoff, Science 300, 783 (2003).
|Oct. 26, 2004
The conventional view is that the universe begins with a bang and expands and cools forever, marked by epochs of inflation, radiation- and matter-domination, and, finally, accelerated expansion. This talk will introduce a radical alternative, the "cyclic model;" which challenges nearly every aspect of the standard picture. In the cyclic model, the universe undergoes periodic evolution, from big bang to big crunch, every trillion years or so, and the key events that shape our current universe take place before the (most recent) bang. Despite the extraordinary differences, the cyclic model reproduces all of the successes of the standard picture with the same degree of precision. We will discuss how future measurements may distinguish the two.
Simons lecturer. Bill Weisberger is host.
|Oct. 29, 2004
(FRIDAY! Coffee & tea 3:45; talk at 4 pm)
|Hans Frauenfelder, Los Alamos
energy landscape and dynamics of proteins
Energy levels have been seminal concepts in chemistry and physics for a long time, starting with the Balmer series in hydrogen and continuing with the energy levels in more complex atoms, molecules, solids, nuclei, and particles. In complex systems, energy levels change to energy landscapes. Understanding the energy landscape is important because transitions in the landscape correspond to motions and reactions. For any complex system, the exploration of the energy landscape is a formidable problem. Glasses and proteins are probably the systems where the energy landscapes are beginning to emerge from experimental, theoretical, and computational studies. Recent results show that the energy landscape of even a simple protein is extremely complex and that the dynamics is controlled not only by the protein proper, but is strongly influenced by motions in the hydration shell and in the bulk solvent.
Joint Chemistry/Physics colloquium. Jin Wang is host.
|Nov. 2, 2004
Grannis, Stony Brook
||The next step for particle physics: the
e+e- linear collider
I will discuss the progress made recently towards realization of TeV scale e+e- linear collider: what are the important physics questions it would address, how does it complement other high energy physics programs, how does one design the collider, recent decisions taken on the choice of technology and steps toward worldwide organization. Will the linear collider be worth the investment?
|Nov. 9, 2004
|Nov. 16, 2004
||Sasha Abanov, Stony Brook||Geometry
and topology of strongly correlated systems
Interactions in many body systems often lead to unusual collective behaviors at a macroscopic scale. Sometimes, macroscopic correlations in such systems can be summarized in the form of an "effective" field theory. I will illustrate an effective field theory approach by several examples from condensed matter physics. Then I will focus on geometrical and topological aspects of an effective description of strongly correlated systems.
|Nov. 30, 2004
||Azi Genak, Queens
Localization in the Time Domain
The challenges and possibilities presented in the study of optical and microwave propagation and localization raise new issues whose resolution clarifies the picture of transport in disordered systems. Measurements of the electromagnetic field make it possible to relate greatly enhanced
fluctuations of local and spatially integrated flux in multiply-scattering samples to the statistics of the underlying wave. Fourier transforming the measured field spectra yields the time evolution of electromagnetic pulses and reveals the growing impact of weak localization in time. The diffusion
coefficient is increasingly suppressed in time, while the degree of intensity correlation grows rapidly in diffusive and localized samples. Since the distribution of wave trajectories within a medium at a given time delay is not affected by absorption or amplification, the role of loss or
gain in wave propagation can be unscrambled.
|Dec. 7, 2004
Poliovirus, Life, and Fear.
Jeronimo Cello, Aniko Paul, and Eckard Wimmer
Poliovirus has been a curse on humans throughout the first half of last century because it caused epidemics of a debilitating if not deadly disease called poliomyelitis (destruction of motor neurons leading to paralysis). Discovered in 1909, enormous research efforts have been expended to nderstand the virus and to prevent the disease. Two excellent vaccines, developed in the nineteen fifties, broke the frightening grip of poliovirus on societies and, indeed, the World Health Organization is currently conducting a campaign to globally eradicate the agent. Nevertheless, poliovirus, one of the best known viruses of all times, is still being studied extensively as model for a large number of RNA viruses. The chemical structure of the virus was elucidated by us in 1981, its three dimensional structure by J. Hogle in 1985. Textbook wisdom states that viruses are obligatory intracellular parasites unable to replicate outside intact cells. In 1991, however, we provided evidence that poliovirus can replicate de novo in a cell free extract. Moreover, in 2002, we showed that the only information necessary to generate poliovirus outside living cells is its "formula", that is, the sequence of its genome available in the public domain. The chemical/biochemical synthesis of poliovirus based exclusively on information from the internet resulted in a deluge of responses, ranging from ethical questions to those of the value of the experiment, bioterrorism, publication of scientific information, and national security. These issues as well as the synthesis of replicating (living?) entities in general will be discussed.
For Spring 2005, go here.