Fall 2011

August 26, 2011
"Coronal Holes" by Elizabeth Dahlburg, '12
3:10 pm
Franklin Miller, Jr. Lecture Hall (Hayes 109)
Please join us for Ms. Dahlburg's senior exercise talk. Abstract: Coronal holes are regions marked by a drop in intensity as seen in solar coronal images. These events can occur in association with coronal mass ejections (CMEs), and as a result of magnetic field reconfiguration. With tens of thousands of man-made objects currently in the Sun-Earth Environment, there is great need for understanding of solar activity and predictive capabilities. This summer I worked on an automated detection routine to track the evolution of coronal holes using the Atmospheric Imaging Assembly (AIA) data from the Solar Dynamics Observatory (SDO) mission, as well as the Solar TErrestrial RElations Observatory (STEREO) mission Extreme UltraViolet Imager (EUVI) data. These instruments provided full solar coverage and a unique opportunity to gain information regarding the global magnetic field topology. Comparing these observational results with those of a potential field source surface model (PFSS) allows us to test our knowledge and understanding of the Sun's magnetic fields. Reception to follow.

September 2, 2011
"Fukushima and the Future of Nuclear Energy in the U.S." by Dr. Richard S. Denning, Professor, Mechanical & Aerospace Engineering, The Ohio State University
3:10 pm
Franklin Miller, Jr. Lecture Hall (RBH 109)
Abstract: Dr. Denning will describe what actually happened in the Fukushima accident and provide an evaluation of the failure in safety practices that led to severe fuel damage. He will also discuss the expected health, environmental, and economic consequences of the event. Risk studies indicate that a similar "station blackout" accident could occur in the U.S. but at a very low probability. Dr. Denning will describe some differences in the capabilities of U.S. plants similar in design to the Japanese plants to mitigate the consequences of such an event. The NRC has issued their 90-day report with recommendations regarding upgrades that could be required in operating plants in the U.S. He will discuss the implications to plans for life extension of current plants, planned power uprates, and prospects for new power plant designs that don't require AC power to achieve safe shutdown.

September 9, 2011
"Minimal Length Scale and Its Effect on Hawking Radiation," Senior Exercise Talk by Patrick Meyers, '12
3:10 pm
Franklin Miller, Jr. Lecture Hall (Hayes 109)
Please join us for Mr. Meyers's senior exercise talk. Abstract: While the search for a formal theory encompassing both Quantum Mechanics and Gravitation is still being developed, certain heuristic results of what will come of that theory can be discussed. Almost all theories of Quantum Gravity postulate a minimal length scale that often relates to the Planck Length (~10-35m). The transition from the idea of a minimal length scale to a minimum uncertainty in position and momentum (Heisenberg's Uncertainty Principle makes no stipulation as to how to deal with infinitesimal values in uncertanties) is non-trivial, but is still a natural one to make. This summer I worked on calculating how the tunneling rate of particles in Rindler Space (the space of uniformly accelerating observers) is affected by a generalized uncertainty principle. In this simple case, the tunneling rate is changed. This is a step towards applying a minimal length scale to Hawking Radiation, which could have an effect on Hawking's original results. Reception to follow.

September 16, 2011
"Coffee and Cigars: Modeling a Hybrid Magnetic/Optical-Dipole Trap for Rubidium 87" - Senior Exercise Talk by Joseph Murphree, '12
3:10 pm
Franklin Miller, Jr. Lecture Hall (Hayes 109)
Abstract: The study of Bose-Einstein condensates (BEC's) from atomic gasses has provided great insight into the nature of quantum mechanics, and much of the experimental work has depended on optical or magnetic traps to capture and cool the atoms. However, each of these traps alone suffers from unique limitations that could be overcome when used in conjunction with each other. Traps consisting of a magnetic trap together with an optical-dipole trap have variously capitalized on this synergy, offering tantalizingly large initial load volumes of ultra-cold atoms that are transferred to solely optical potentials. In preparation for the installation of such a trap for Rubidium 87, we designed a computational model to determine ideal starting parameters for the experimental set-up. Furthermore, we used the program to design a novel adiabatic cooling and compression procedure that would result in a near-degenerate, optically-contained atomic cloud. Reception to follow.

September 23, 2011
"Exploring the Dark Side of Our Universe" by Mustafa Amin, Pappalardo Fellow in Physics: 2008-11, Massachusetts Institute of Technology
3:10 pm
Franklin Miller, Jr. Lecture Hall (RBH 109)
Abstract: Over the past 70 years, we have discovered that most of the matter in our universe hardly interacts with normal matter (eg. atoms or light) but nevertheless makes its presence felt via its gravitational pull. In addition, in the 1990's we discovered that the distant galaxies are moving away from each other at an ever increasing rate. The race is on to understand the nature of this weakly interacting matter (dark matter), whose clustering provides the network in which galaxies are embedded and the mysterious component (dark energy) which is responsible for the accelerated expansion of space. I will mainly concentrate on what we have learnt about dark matter so far from theoretical, observational and computational efforts and highlight current and future efforts directed towards revealing its nature. Reception to follow.

September 30, 2011
"My First Entanglement: A Senior Exercise Talk" by Robert Fine, '12
3:10 pm
Franklin Miller, Jr. Lecture Hall (Hayes 109)
ABSTRACT: Modern quantum entanglement research is limited to mostly large research institutions, but given access to specific equipment, it is possible for an undergraduate laboratory to construct a quantum entanglement apparatus. Near single-mode coherent light of wavelength ~ 405nm sent through a non-linear beta barium borate (BBO) crystal will undergo spontaneous parametric down-conversion into infrared light of comparable quality. This process produces pairs of photons that exit the crystal such that their net directionality is consistent with the momentum, etc. of their parent as well as with the conservation of energy. Some fraction of these pairs can only be described collectively by a single quantum state, i.e. these pairs are entangled. The useful output of this apparatus is a source of polarization-correlated entangled photons, which I am using to conduct basic entanglement experiments and more. Reception to follow.

October 14, 2011
"Wiggle, Jiggle, Dance, and Giggle: Brownian Motion of Particles in Confined Geometries" by Jan Kmetko, Assistant Professor, Department of Physics, Kenyon College
3:10 pm
Franklin Miller, Jr. Lecture Hall (RBH 109)
Abstract: Imaging and analyzing trajectories of single particles undergoing Brownian motion provides information on the diffusion coefficients of these particles. In many systems, individual particles diffuse within confined spaces, for example, biomolecules within organelles of a cell or small molecules within interstitial spaces of macromolecular crystals. To understand how the geometry and the size of the confining space affects diffusion, we have used a high-sensitivity EM-CCD camera to image trajectories of fluorescently tagged 100nm-size colloidal particles trapped within micron-sized defects of colloidal crystals. We also measure the diffusion of fluorescent dye (small molecule) confined within the pores of biological crystal by the technique of fluorescence recovery after photobleaching (FRAP). Knowing the diffusion of small molecules within biological crystals is useful for many applications: cross-linked protein crystals have recently been proposed for industrial and clinical applications as stable catalysts and as sensitive elements for (bio)chemosensors. We construct a curve relating the diffusion coefficient of dye to the channel size within the crystals, by fitting our imaged profiles to an analytic solution of the diffusion equation. Reception to follow.

October 21, 2011
"Finding Mass at the LHC: What Is The Higgs and How Do We Look For It?" by Matthew Buckley, '03, Schramm Fellow Theoretical Astrophysics Group Fermilab
3:10 pm
Franklin Miller, Jr. Lecture Hall (RBH 109)
Abstract: The Large Hadron Collider is the highest-energy particle accelerator in the world, and has now been running for over a year. The primary physics goal of the LHC is to find the Higgs boson, which allows the known particles to become massive. In this talk, I will give an overview of the LHC, the Higgs mechanism, and the current status of the experimental search. Reception to follow.

October 28, 2011
"100 Years of Superconductors - 50 Years of BCS Theory" by Leon Cooper, Nobel Laureate, Brown University
3:10 pm
Franklin Miller, Jr. Lecture Hall (RBH 109)
Dr. Leon Cooper, Nobel Laureate, Thomas J. Watson, Sr. Professor of Science, Brown University Abstract: Professor Cooper will join us for a virtual colloquium via video link from Providence, Rhode Island. Professor Cooper will talk about the history of our understanding of superconductivity and the story of how phenomenon became science. Reception to follow.

November 4, 2011
"Cold Atom Diffraction" by Janine Shertzer, Distinguished Professor of Science, Professor, Physics - College of the Holy Cross
3:10 pm
Franklin Miller, Jr. Lecture Hall (RBH 109)
The wave-particle duality is fundamental to atomic physics. Under special conditions, we can observe wave properties of matter. The wavelength is h/p, where h is Planck's constant. For very cold atoms, the wavelength is large enough that one can design diffraction gratings and observe an interference pattern. I will discuss how lasers can cool atoms to approximately 10 microkelvin, and why a Zip disk can be used as an atomic diffraction grating. Optical interference (like Young's double slit experiment) can be understood theoretically by solving the wave equation. To understand the interference of cold atoms, one must solve the Schroedinger equation. My research students and I carried out the first quantum calculation for atomic diffraction from a periodic magnetic surface. Our results predict the location and relative intensity of the interference peaks as a function of experimental parameters.

November 10, 2011
Annual Donald B. Hamister Distinguished Lecture in Physics - Dr. Charles H. Bennett, IBM Research
7:30 pm
The Beulah Kahler Theater - Kenyon College Athletic Center
Dr. Charles H. Bennett, IBM Research, will present a public lecture entitled: "Quantum Information, the Ambiguity of the Past, and the Complexity of the Present." Abstract: Quantum theory, in particular the theory of entanglement, provides a coherent picture of the physical origin of randomness and the growth and decay of correlations. This picture is strikingly different, but we will argue more satisfying, than the deterministic universe of classical mechanics. Quantum theory helps explain why the future is more uncertain than the past, and how correlations can become macroscopic and classical by being redundantly replicated throughout a system's environment. The most private kind information, exemplified by which path a particle takes in the famous two-slit experiment, exists only transiently: after the experiment is over no record remains anywhere in the universe of what "happened". At the other extreme is information that has has been replicated and propagated so widely as to be infeasible to conceal and unlikely to be forgotten. This is the kind of information politicians tend to lie about. Modern information technology has caused an explosion of such information, eroding privacy while making it harder for tyrants to rewrite the history of their misdeeds; and it is tempting to believe that all macroscopic information is permanent, making such cover-ups impossible in principle. But we argue, by comparing entropy flows into and out of the Earth with estimates of the planet's storage capacity, that most macroscopic classical information---for example the pattern of drops in last week's rainfall---is impermanent, eventually becoming nearly as ambiguous, from a terrestrial perspective, as the which-path information of an interferometer. Finally we discuss prerequisites for a system to accumulate and maintain in its present state, as our world does, a complex and redundant record of at least some features of its past. Reception to follow.

November 11, 2011
"Landauer's Principle, Reversible Computation, and Maxwell's Demon" by Dr. Charles H. Bennett, IBM Research
3:10 pm
Franklin Miller, Jr. Lecture Hall (RBH 109)
The second law of thermodynamics is famous having manifestations that seem to have nothing to do with heat or work. One of the newest of these avatars of the second law, suitable for our information age, is Landauer's principle, "No physical process has as its sole result the erasure of information." We discuss the theory of reversible computation by ideal Brownian computers modeled on the genetic apparatus, modern experiments making Maxwell's demon visible for the first time, and the thermodynamics of error-correction in Brownian automata that, like real enzymes, are less than ideal.

December 2, 2011
"Micro-DLS: Diffusion Measurements with Laser Spectrocsopy" by David Somers, '12
3:10 pm
Franklin Miller, Jr. Lecture Hall (Hayes 109)
Please join us for David Somer's senior exercise talk. Abstract: Measuring diffusion coefficients of aqueous particles is a common task in biophysics, and we have pursued several methods of doing so. The most successful of these has been an adaption of a Dynamic Light Scattering (DLS) apparatus to a femtoliter-scale using a LeicaDMI4000 Microscope. Our method produces results consistent with the existing apparatus, but has several key advantages; for example, we have used this device to measure the effective diameter of aqueous lysozyme proteins, which are too small for the older apparatus to measure. We have also explored other methods of measuring diffusion, including Fluorescence Correlation Spectrocsopy (FCS), Photon Arrival-time Interval Distribution (PAID) Analysis using Time-Amplitude Converters (TACs), and a novel analysis using a PCI-6602 80MHz counter and software designed in LabVIEW. We hope to finalize a low-cost method for precise, localized, and real-time measurement of diffusion. Reception to follow.