Colloquia in Academic Year 2009-2010

Dept. of Physics & Astronomy, Stony Brook University


Colloquium committee: Michael Zingale (chair), Meigan Aronson, Axel Drees, Hal Metcalf
Coffee & Tea served at 3:45 pm.  Talk begins at 4:15 pm.  Location: Harriman 137 (bottom of square C4 on the campus map)

 

Spring 2010 colloquia


(colloquia already given are listed here):

DateSpeakerTitleLocal Host

 

Colloquia already given in academic year 2009/2010:


DateSpeakerTitleLocal Host
Sept. 1 Karin Rabe
Rutgers University
Designer oxides that work
(Special NYCCS Colloquium)
Functional oxides, characterized by high sensitivity to applied fields and stresses, are of great current interest both for their fundamental physics and for technological applications including transducers, energy conversion, and information storage. In perovskite oxides, layered perovskites and other complex-structured oxide families, a wide variety of distorted equilibrium phases can be produced by the freezing-in of one or more lattice instabilities of an appropriate high-symmetry reference structure. In this talk, I discuss how the information from computational first-principles studies of these systems provides guidance for altering the balance of the competition of instabilities of different character under conditions characteristic of epitaxial thin films, superlattices, and nanoparticles, leading to the realization of novel phases with structure and properties different from those of the bulk equilibrium phase, as well as desirable functional behavior near the phase boundaries. Examples presented will include the observation of epitaxial-strain-induced ferroelectricity in perovskite titanates and manganates, with discussion of the additional possibility of multiferroism and magnetoelectric coupling in magnetic oxide systems.

[recorded movie]

Michael Zingale
Sept. 8 Laszlo Mihaly
Stony Brook University
Chair's Colloquium N/A
Sept. 15 Jerry Bernholc
NCSU
Computational Nano and Bio Physics: The Era of Applied Quantum Mechanics
(Special NYCCS Colloquium)
It is already possible to predict the properties of new and artificially structured materials entirely by computations, using atomic numbers as the only input. The rapid progress in computational science is expected to continue, which should eventually enable the “design” of nano- and bio- materials with tailor-made properties largely on a computer, with only relatively few final candidates being evaluated experimentally. Although this goal is still some time in the future, current advances in multiscale methods and petascale computing promise breakthroughs that will affect many areas of science, technology and medicine. This talk will review the status and prospects of such calculations, using three examples from the speaker’s work: (i) in molecular electronics, predictions of negative differential resistance in a wide range of organic-molecule-based structures; (ii) development of methodology for large-scale quantum-mechanical simulations of solvated biomolecules and its first applications to unraveling the role of copper in prion and Parkinson’s disease proteins; and (iii) mechanisms and predictions of ultrahigh electric power storage in ferroelectric polymers.

[recorded movie]

Michael Zingale
Sept. 22 Steve Smith
Stony Brook University
The Photophysics of Vision
Rhodopsin is a highly specialized G protein-coupled receptor (GPCR) that is activated by the rapid photochemical isomerization of its covalently bound 11-cis retinal chromophore, aka vitamin A. Absorption of light results in the cis-to-trans conversion of the retinal along a torsional coordinate in the electronic excited state of molecule in less than ~200 femtoseconds. The rapid structural change in the retinal leads to steric strain in the receptor, which is released on the timescale of milliseconds and causes a conformational change in the receptor. I will describe structural studies using Nuclear Magnetic Resonance (NMR) spectroscopy to describe how this visual receptor transduces light into a chemical and biological signal.

[recorded movie]

Hal Metcalf
Sept. 29 no colloquium—classes on Monday schedule
Oct. 6 Kiko Galvez
Colgate University
Quantum Interference of Light: From Fundamentals to Qubits
Recent technological advances have allowed numerous fundamental tests of quantum mechanics via violations of Bell's inequalities of various forms and situations. The use of quantal systems to encode and manipulate information in a non-classical way has led to the rise of a new interdisciplinary field of quantum information. At the heart of both is quantum interference. This rise to prominence has also led us to reconsider how we introduce quantum mechanics in instruction, moving away from "shut up and calculate" to measuring violations of Bell's inequalities as an undergraduate lab. At the colloquium I will present several experiments on quantum interference of light with the thread of reinventing how to introduce quantum mechanics even to first year students, but also understanding the more sophisticated role that photons play in discovering new ways in which quantum mechanics can be implemented for quantum information.

[recorded movie]

Hal Metcalf
Oct. 13 Pierre Thibault High-resolution imaging with coherent X-ray scattering
In the last decade, the development of techniques commonly grouped under the name "coherent diffractive imaging" (CDI) has greatly expanded the means whereby spatial information can be collected using radiation. After giving a general overview of CDI, I will describe recent results obtained at the Paul Scherrer Institut with an improved imaging method. Called "scanning X-ray diffraction microscopy" (SXDM), the technique shares the elegance and the high-resolution potential of many CDI approaches while offering increased reliability and robustness. I will put special emphasis on the underlying algorithmic developments, illustrating the beneficial interplay between experiment and theory.

[recorded movie]

Chris Jacobsen/Michael Zingale
Oct. 20 David Mandrus
ORNL
Breaking the Tyranny of Copper: The Emergence of a New Generation of High-Tc Superconductors Based on Iron
In this talk a brief history and materials overview of the new layered Fe-based superconductors will be presented, followed by a discussion of recent experimental work on the new materials from Oak Ridge National Laboratory including some of the first neutron scattering results from the Spallation Neutron Source.

[recorded movie]

Meigan Aronson/Laszlo Mihaly
Oct. 27 Grover Swartzlander
RIT
Focusing light using only polarization
I will show how light can be focused by using only polarization elements. Surprisingly, both the amplitude and phase of a beam may be arbitrarily controlled with computer-generated elements called vectographs, combined with a quarter wave retarder. Vectographs are non-uniformly dyed polarizers that have been used for years to produced gorgeous colorful stereoscopic images (and even a few movies). This talk will discuss our recent fabrications of the first vectographic lens and vectographic vortex. This novel approach to beam shaping and wavefront control may one day rival holography.

[recorded movie]

Hal Metcalf
Nov. 3 Steve Peggs
BNL
Thorium Energy Amplifiers and Proton Therapy: New concepts—fast accelerator physics challenges
Global interest in accelerator driven sub-critical Thorium Energy Amplifiers (ThorEA) is exploding. Key to the eventual construction of full scale nuclear reactors for sustainable electricity generation is the demonstratation of ultra-reliable MW-class proton drivers at 1 GeV or higher. The fundamental accelerator R&D required for such a demonstration is quite similar for both Fixed Focusing Alternating Gradient accelerators (FFAGs) and for Very Rapid Cycling Synchrotrons (VRCSs). This same R&D would enable a low power 250 MeV FFAG or VRCS to be used for proton therapy with pulse repetition rates of about 1 kHz.

[recorded movie]

Axel Drees
Nov. 10 Jim Lattimer
Stony Brook
Neutron Star Structure and the Equation of State
Neutron stars provide a unique laboratory with which to study cold, dense matter. The quantities of primary interest are the maximum mass and the typical radius of a neutron star. It is demonstrated how these quantities are related to the relative stiffness of neutron-rich matter and the density dependence of the nuclear symmetry energy. The possible measurements of these quantities through heavy-ion collisions and parity-violating electron scattering from neutron-rich nuclei are discussed. In addition, there are several recent observations, including thermal emissions from cooling neutron stars, pulsars and binary pulsars, and thermonuclear explosions from accreting stars, that are competing in the quest for the pressure-density relation of dense matter.

[recorded movie]

Michael Zingale
Nov. 17 Dmitri Kharzeev
BNL
Chiral symmetry and parity-odd effects in hot QCD matter
I will address the role of chiral symmetry and parity invariance in the properties of hot and dense quark-gluon matter. The possibility of parity-odd effects in this matter will be discussed. Local parity violation can manifest itself in heavy ion collisions at RHIC through the spatial separation of positive and negative particles with respect to the reaction plane. The charge separation induces the electric dipole moment of the produced hot quark-gluon matter; it stems from the interplay of strong magnetic field in the early stage of the heavy ion collision and the presence of topological configurations in hot matter ("the chiral magnetic effect"). This effect is enhanced in the deconfined and chirally symmetric quark-gluon plasma phase of strongly interacting matter because it requires the separation of quarks over a large distance. Recently parity violation has been studied at RHIC, with an exciting result. The effect has interesting applications for the cosmology of the Early Universe, and has analogs in condensed matter physics (quantum wires and graphene), and in astrophysics (particle acceleration in cosmic strings).

[recorded movie]

Axel Drees
Nov. 24 Michael Rosenthal
BNL
International Atomic Energy Agency Safeguards: How IAEA Inspectors became Detectives.
The NPT entered into force in 1970. It required that all non-nuclear weapon states parties accept the application of safeguards "with a view to preventing diversion of nuclear energy from peaceful uses to nuclear weapons or other nuclear explosive devices. Procedures for the safeguards required by this Article shall be followed with respect to [nuclear] material whether it is being produced, processed or used in any principal nuclear facility or is outside any such facility. The safeguards required by this Article shall be applied on all [nuclear] material in all peaceful nuclear activities" of the State."

The implementation of this obligation was assigned to the IAEA and is implemented in accordance with a model safeguards agreement that was adopted by the IAEA Board of Governors in 1971. Known as INFCIRC/153, this agreement established material accountancy as a measure of fundamental importance with containment and surveillance as important complementary measures and assigned to the IAEA both the right and the obligation to "ensure that safeguards will be applied ... on all [nuclear] material in all peaceful nuclear activities of the state.

Implementation of NPT safeguards, thus, began in the early 1970's with a focus on material accountancy. Not surprisingly, the primary focus of the IAEA's safeguards effort was detecting diversions on the basis of this measure. Although not surprising, far too little emphasis was placed on measures that would help the IAEA to fulfill its obligation to apply safeguards to all nuclear material. This situation resulted not only because the IAEA lacked clear tools to do so. There was also pressure from states to reduce the burdens of safeguards. The flaws in this approach were highlighted dramatically by the discovery in Iraq of a clandestine nuclear weapon program in 1991. This discovery triggered a program of work that resulted in the adoption in 1997 of a new safeguards agreement, the Model Additional Protocol. Under the new safeguards agreement, the IAEA inspector is explicitly empowered to be a "detective," i.e., to look for undeclared nuclear activities. This presentation traces the way in which this transformation took place and highlights the many strengths and some weaknesses of the new safeguards system.

[recorded movie]

Michael Zingale
Dec. 1 Barbara Jacak
Stony Brook University
Quark Gluon Plasma: From Particles to Fields?
Quantum chromodynamics predicts melting of hadrons into a plasma of quarks and gluons at high temperature and/or density. High energy collisions of heavy ions have been studied at RHIC to create this plasma and measure its properties, yielding some big surprises. The quark gluon plasma behaves as a perfect, exceedingly opaque hot liquid. It appears to be strongly coupled, with phases similar to some condensed matter systems and dense electromagnetic plasmas. Attempts to quantitatively reproduce the observed properties with perturbative QCD are not successful. New theoretical and experimental approaches are underway to understand the screening, correlations, and underlying degrees of freedom in strongly coupled QCD matter.

[recorded movie]

Axel Drees
Dec. 8 Shivaji Sondhi
Princeton University
Spin Ice and Magnetic Monopoles
The "spin ice" materials are elegant laboratories for the physics of geometrical frustration in magnets. I will describe their basic statistical mechanics, the connection to real ice, a central puzzle of their existence and its resolution leading to the uncovering of an emergent gauge field as well as the magnetic monopoles of the standard magnetic gauge field advertised in the title.

[recorded movie]

Meigan Aronson

Winter Break
 
Jan. 26 Bob Rosner
Chicago
Why do I compute?
The nondimensional numbers characterizing most astrophysical phenomena are sufficiently large that direct numerical simulations describing these phenomena are not just difficult, they are most likely even in principle impossible. Despite this inconvenient fact, modern astrophysics clearly revels in modeling astrophysical phenomena, and the skeptical observer might well ask, to what effect?? I will discuss my answer to this question.

[recorded movie]

Michael Zingale
Feb. 2 Jerry Gollub
Haverford and Penn
Swimming Dynamics of Algae Cells and the Fluid Motion they Produce
This talk concerns the swimming of single algae cells only 10 micrometers across. These and other algae cells produce a significant fraction of the earth's oxygen. Their swimming involves the synchronized beating of appendages known as flagella or cilia, which are also important for many other types of cells, such as those lining the interior of the lung.

In work published in Science, we showed [1] that the coordination of the two flagella of the algae cells is is possible because of forces transmitted between them through the intervening fluid. In a "Perspective" written about this work in Science, two experts in the field comment that the coordinated motion of flagella allows the cells to enhance their nutrition and may have contributed to the evolution of multi-cellular organisms.

Yet about 5% of the time the cells choose to make their flagella beat at different rates, which causes the cells to turn sharply. Why would they do this? One possibility is that the cells need to avoid contact with predators. The biochemical means by which the organism makes this choice, and the role of chance in the process, are not yet understood.

In related work that appeared in Physical Review Letters, we studied the stirring of the fluid by swimming cells, which also affects their access to nutrients. The natural Brownian motion of tracer particles immersed in the fluid is enhanced by the swimmers in a remarkable way.

This work was done in collaboration with the group of Raymond Goldstein at Cambridge UK

[1] Marco Polin, Idan Tuval, Knut Drescher, J.P. Gollub, and Raymond E. Goldstein, "Chlamydomonas swims with two "gears" in a eukaryotic version of run-and-tumble locomotion", Science 24 July 2009. Accompanied by a Perspective by Roman Stocker and William M. Durham: "Eukaryotic flaggelar synchronization: tumbling for stealth?"

[recorded movie]

Hal Metcalf
Feb. 9 John Kimball
Albany
Physics of Sailing
Applications of physics to sailing range from elementary mechanics to the theory of turbulence. A simple example is the relation between torques and capsizing sailboats. A less trivial example is Newton’s demonstration that the wind’s force is proportional to the square of the wind speed. Less ancient science is needed to explain other aspects of sailing physics. The invariance of Gaussian curvature is a key to understanding sail shapes. Fluid mechanics determines lift and drag forces. The constantly fluctuating wind is an example of turbulence. Waves and wakes add a great deal of complexity to models of sailboat motion. Fermat’s principle and Hamiltonian mechanics describe the ideal sailing strategy. Some aspects of sailing are more of an art than a science, and sometimes physicists should just sit back and enjoy the ride.

[recorded movie]

Phil Allen / Meigan Aronson
Feb. 16 Richard Ellis
Caltech
Observational Constraints on Dark Energy: Consumer's Guide
The discovery that our universe is accelerating poses a major challenge for physical cosmology; indeed the moniker `dark energy' encapsulates our ignorance of its origin. Much effort is being invested to improve the observational constraints, both with current facilities and in proposing future missions and instruments. But without a theory to target, the strategy is not always clear and much work needs to be done before any of the three principal methods (supernovae, gravitational lensing and large scale structure) can be exploited to the precision necessary. I will review these challenges in the context of current and projected datasets.

[recorded movie]

Michael Zingale
Feb. 23 Nergis Mavalvala
MIT
Interferometric gravitational wave detectors and the search for the elusive waves
As the Laser Interferometer Gravitational-wave Observatory (LIGO) and its international counterparts are carrying out the most sensitive astrophysical searches to date, we enter an exciting new era of gravitational wave astronomy. A report on the present status and recent results from the currently operational LIGO interferometers will be followed by a discussion of next-generation detectors and the path to higher sensitivity future detectors.

[recorded movie]

Hal Metcalf
Mar. 2 David Larbalestier
FSU
New high-Tc superconductors – can they transform superconducting magnet technology?
Kamerlingh Onnes went to the International Institute of Refrigeration in Chicago in 1913, two years after discovering superconductivity in Hg, with a conceptually well developed vision for making a 10 Tesla magnets with superconductors. But actually superconducting magnets took until the 1960s to appear. The vital breakthroughs were many – a proper understanding of the difference between type I and type II superconductors, the need to apply alloyed rather than pure superconductors, and the need to fabricate them in affordable forms that are stable against electromagnetic instabilities. Nb-47wt%Ti and Nb3Sn were rapidly developed in the 1960s and enable this technology, allowing magnets as diverse as the 9-20 T solenoids in many physics labs, the Large Hadron Collider, ITER, and the ubiquitous MRI and NMR magnets. But to use only Nb-base materials both limits the accessible fields to less than about 23 T and places a major divide between those interested in the more exotic coupling mechanisms of superconductivity found in cuprates and pnictides, which allow transition temperatures well over 100 K and critical fields that are at least 5 times those of Nb3Sn. Recent tests of small coils at the magnet lab have led to superconducting magnets operating at fields up to almost 34 T, about 50% more than is possible with any Nb-base magnet. As we approach the centenary of the discovery of superconductivity and searches for even higher Tc superconductors take root, I will discuss the constraints that magnet materials place on new superconducting materials.

[recorded movie]

Meigan Aronson
Mar. 9 Charles Kane
U. Penn
Topological Insulators and Topological Band Theory
A topological insulator is a material with a bulk excitation gap generated by the spin orbit interaction, which is topologically distinct from an ordinary insulator. This distinction -- characterized by a topological invariant -- necessitates the existence of conducting states on the sample boundary which have a massless Dirac dispersion relation. These materials have attracted considerable interest as a fundamentally new class of insulators with applications from quantum transport to quantum computing. In this talk we will outline our theoretical discovery of this electronic phase and describe recent experiments in which its signatures have been observed in both two and three dimensional systems. We will close by arguing that the proximity effect between an ordinary superconductor and a 3D topological insulator leads to a novel two dimensional interface state which may provide a new venue for realizing proposals for topological quantum computation. [recorded movie]
Sasha Abanov
Mar. 16 Dam Son
INT / University of Washington
Quark gluon plasma and gauge/gravity duality
The strongly coupled nature of the quark gluon plasma created at the Relativistic Heayv Ion Collider poses a big challenge for theory. I will discuss recent attempt to use gauge/gravity duality, a by-product of string theory, as a tool to understand properties of strongly coupled systems. This line of thinking has lead to the identification of the ratio of viscosity to volume density of entropy as a measure of interaction strength in the quark gluon plasma. I will also describe recent attempts to use gauge/gravity duality for condensed-matter systems, including the system of fermions with resonantly tuned interaction which has been realized with ultracold trapped atoms.

[recorded movie]

Jacobus Verbaarschot / Michael Zingale
Mar. 23 Nati Seiberg
IAS
Supersymmetry and its Breaking
Supersymmetry will be presented as an extension of our ideas about space and time. We will review the motivation for discovering supersymmetry at the LHC and will argue that this symmetry must be broken. The discussion of supersymmetry breaking will lead us to conclude that the world is likely to be in a metastable state.

[recorded movie]

Martin Rocek / Michael Zingale
Mar. 30 no colloqium—Spring Break
Apr. 6 Stephen Julian
Toronto
New Phases of Matter at Quantum Phase Transitions
Changes of state that occur at the absolute zero of temperature are called "quantum" phase transitions. Because absolute zero is unattainable, their study at first seems irrelevant, but as I will attempt to explain in this talk, quantum phase transitions offer a systematic way to produce new kinds of ordered states in condensed matter. Moreover, they have given rise to conceptual tools that have really changed the way we think about the quantum mechanics of solids. I will illustrate these points with a number of experimental studies carried out at high pressure, high magnetic fields and very low temperatures.

[recorded movie]

Meigan Aronson
Apr. 13 Ken Dill
University of California, San Francisco
Nonequilibrium statistical mechanics of few-particle systems, such as in biology and nanotechnology
We are interested in dynamical processes, such as Fick's law of particle diffusion, Fourier's law of heat diffusion, and master equations for chemical reaction dynamics, applied to very small scales and to very few particles, such as occur inside biological cells, or in single-molecule experiments. To explore the fluctuations, we use a variational approach to dynamics called Maximum Caliber, related to the Maximum Entropy approach used in equilibrium statistical mechanics. To test the theory, we have been exploring microfluidics experiments on few-particle colloidal systems and beads trapped in laser-trap energy wells.

[recorded movie]

Laszlo Mihaly
Apr. 20 Jeffrey Grossman
MIT
Understanding and Improving Energy Conversion and Storage Materials from Atomic-Scale Simulations
Classical and quantum mechanical calculations are employed to understand important microscopic mechanisms in energy conversion and storage materials. Our goal is to predict key properties that govern efficiencies in these materials, including structural and electronic effects, interfacial charge separation, electron and hole traps, excited state phenomena, band level alignment, synthesis, and binding energies. Examples of our work in the areas of photovoltaics, thermoelectrics, hydrogen storage, and solar fuels will be presented. We use these examples to illustrate how computational approaches can improve our understanding and lead to more efficient materials and ultimately devices. More broadly, the close coupling of predictive simulation with experiments will be discussed as a promising strategy for both obtaining fundamental scientific insights and developing new energy conversion and storage materials with high efficiencies and the potential for large-scale impact

[recorded movie]

Kostya Likharev
Apr. 27 Marla Geha
Yale 
The Darkest Galaxies
In the past several years, fourteen Milky Way satellite galaxies have been discovered, more than doubling the known population. These newly discovered ``ultra-faint'' galaxies have emerged as the least luminous and most dark matter-dominated galaxies in the known Universe. They are dramatically reshaping our understanding of galaxy formation and may hold the keys to deciphering the nature of dark matter. I will review our current understand of the ultra-faint galaxies, focusing on the constraints these objects provide on dark matter.

[recorded movie]

Michael Zingale
May 4 graduate director Award's colloquium

[recorded movie]

N/A