Fall 2009

September 11, 2009
"Unraveling Entanglement: Correlation and Sharability within Quantum Mechanics and Beyond", Senior Exercise Talk by Peter Johnson, '10
3:10 pm
Franklin Miller, Jr. Lecture Hall (RBH 109)
Abstract: The mysterious phenomenon of quantum entanglement has puzzled physicists for decades. Two entangled particles behave in highly correlated ways -- an almost "telepathic" connection that can extend over any distance. In quantum mechanics, no third particle is able to tap into this link and share in the entanglement relationship. This fact is called monogamy of quantum entanglement. In this talk, we will explore weaker degrees of entanglement that may be shared among up to three, four, or N particles. The ideas of sharability and monogamy are clearer if we approach them in a more general way, using a simple framework that describes any sort of correlated behavior, including that of entangled quantum particles. The monogamy of quantum entanglement does not depend on the detailed mathematics of quantum theory, but can be deduced directly from the observed correlations of pairs of particles. Reception to follow.

September 25, 2009
"Electron Nuclear Double Resonance on P1 Centers in Diamonds," Senior Exercise Talk by Nirajan Mandal, '10
3:10 pm
Franklin Miller, Jr. Lecture Hall (RBH 109)
Abstract: A diamond is an aesthetically pleasing gem, but it is being widely used in industrial applications, such as cutting and grinding tools, because it is the hardest material known. High demand for diamonds has advanced the technique of synthesizing diamonds at a rapid pace. Today, one can dope diamonds with different elements, not only to get colorful stones, but also to create materials with exciting properties, such as magnetism. It is also expected that one could build quantum devices using these doped materials. Electron paramagnetic resonance (EPR) is one of the techniques that can be used to study diamonds with magnetic properties. In this talk, I will briefly discuss how EPR works and how this technique is applied to studying diamond doped with Nitrogen. Nitrogen has a magnetic nucleus which is coupled to one of the neighboring carbon electrons. One can study these nuclei using nuclear magnetic resonance (NMR). Since the system is a coupled system, one can use an electron nuclear double resonance (ENDOR) experiment to study the magnetic properties of these diamonds. Reception to follow.

September 30, 2009
"The Origin of the Universe and the Arrow of Time " by Sean Carroll, Caltech
3:10 pm
Franklin Miller, Jr. Lecture Hall (RBH 109)
Abstract: Over a century ago, Boltzmann and others provided a microscopic understanding for the tendency of entropy to increase. But this understanding relies ultimately on an empirical fact about cosmology: the early universe had a very low entropy. Why was it like that? Cosmologists aspire to provide a dynamical explanation for the observed state of the universe, but have had very little to say about the dramatic asymmetry between early times and late times. I will argue that the observed breakdown of time-reversal symmetry in statistical mechanics provides good evidence that we live in a multiverse. Reception to follow.

October 9, 2009
Senior Exercise Talks by Evan Pease and William Koehler
3:10 pm
Franklin Miller, Jr. Lecture Hall (RBH 109)
Evan Pease, 10 "Time-Reversal Symmetry Breaking in Superconducting Filters" ABSTRACT: Evans talk will cover his foray into the world of high-temperature superconductors during his REU research at Hope College (Holland, MI). High-temperature superconductors (HTS) make compact and low-loss filters for microwave circuits. HTS filters are known to produce harmonic and intermodulation distortion (IMD), which set the limits for use in microwave technologies, and whose observation provides a better physical understanding of the electrodynamics of the HTS materials. Multi-tone measurements can be performed to detect the distortion, and a three-tone technique developed at Hope College that Evan implemented in his research this summer allows simultaneous measurement of even and odd order distortion currents. Despite earlier predictions of only odd order nonlinearity arising from HTS materials, Evan observed both even and odd order distortion. This is experimental evidence of time-reversal symmetry breaking in superconducting current. Evan also observed interesting characteristics near the samples' transition temperature, Tc. The catastrophic increase in only the odd order IMD levels near Tc is consistent with the expectations of the nonlinear Meissner effect in HTS. The absence of such a catastrophe in the even order distortion indicates a higher order of time-reversal symmetry in conduction near Tc. William Koehler, 10 "Plutonium Levels in Spent Fuel: A Look into Nuclear Safeguards" ABSTRACT: Most of the world's plutonium (Pu) is stored in commercial spent fuel assemblies and yet, as of today, no method to directly measure the Pu mass in these assemblies exists. In an effort to assist the International Atomic Energy Agency (IAEA) in safeguarding nuclear facilities and material, Los Alamos National Laboratory is leading a multi-laboratory effort to investigate different nondestructive techniques for quantifying Pu mass in spent nuclear fuel. Since no one nondestructive technique can quantify Pu on its own, several techniques need to be integrated into a final product. The starting point for this integration is understanding how each technique functions as a standalone instrument. One technique is delayed neutron counting in which a neutron source (deuterium-tritium, deuterium-deuterium, or 252Cf) creates a bursts of neutrons next to a fuel assembly causing fissions in the uranium and Pu isotopes present in the fuel. Fission fragments are produced by the fissions and these fragments emit delayed neutrons. The resulting signal can be analyzed to determine the fissile content (sum of Pu and U) of the spent nuclear fuel. Reception to follow.

October 16, 2009
Dust in the Vacuum of Space: Measuring the Reflective Properties of Astronomical Silicates by Nathan P. Lourie, '10
3:10 pm
Franklin Miller, Jr. Lecture Hall (RBH 109)
Senior Honors Talk by Nathan P. Lourie, '10 Astronomical dust clouds permeate the farthest reaches of space and the interstellar medium. These clouds are comprised primarily of microscopic silicate and carbonate condensates, formed by the cooling of hot gas outflows from stars and nebulae. Dense dust clouds serve as a breeding ground for new generations of stars and planets, yet shield these objects from direct observation. Light emitted from stars within the clouds is scattered by minute particles in the surrounding dust. As this visible light travels through the dust, it is reprocessed into infrared radiation that can be detected using satellite and ground-based observatories. Only by understanding the reflective, transmissive and emmissive properties of astronomical dusts can astronomers begin to be able to analyze the light from various sources within the clouds. Current understanding of these properties is based on dated theoretical models of dust particles. In support of a host of proposed infrared satellite missions, NASA has introduced a new project to characterize the optical properties of silicate dusts through a variety of laboratory measuring techniques. In this talk I will discuss my work for NASA designing and assembling an integrating sphere reflectometer to measure the reflectance of dust samples at a variety of infrared wavelengths and cryogenic temperatures. Reception to follow.

October 23, 2009
"The accelerating Universe and Dark Energy " by Claudia de Rham, Perimeter Institute for Theoretical Physics and McMaster University
3:10 pm
Franklin Miller, Jr. Lecture Hall (RBH 109)
Abstract: Over the past ten years, a wealth of observational data from independent probes has merged on a successful standard model of cosmology, describing the evolution of the Universe and its composition. Despite its success, this cosmological paradigm presents many mysteries, such as the origin and nature of "Dark Energy" that causes the current Universe to accelerate. Dark Energy is believed to be a smooth component, have a negative pressure and comprises about 70% of the total energy of the current Universe. Although such a fluid is typically expected from particle physics, the observed density of Dark Energy is 120 orders of magnitude smaller than anticipated. In this talk, I will review the essence of the problem and present different scenarios capable of tackling this mystery. Reception to follow.

October 30, 2009
"The Birthplace of Stars: Giant Molecular Clouds" by Nia Imara, Department of Astronomy, University of California, Berkeley
3:10 pm
Franklin Miller, Jr. Lecture Hall (RBH 109)
Abstract: Giant molecular clouds, such as those in the famous Great Nebula in Orion, are important to astronomers for a number of reasons. These extremely massive entities (ranging from 10⁴ to 10⁶ times the mass of the Sun) are where all stars are born. Therefore, in order to construct a comprehensive picture of stellar and, ultimately, galactic evolution, it is necessary to understand the properties of giant molecular clouds (GMCs) and how they are formed. In this presentation, I will discuss properties of GMCs, some of the proposed theories for their formation, and how well these theories match up with observations. In one study, I was able to trace distribution of molecular clouds in a galaxy neighboring the Milky Way, the Large Magellanic Cloud-interesting to astronomers because of its primordial environment. I will also present results from my research showing that it is important to consider the dynamics not only of GMCs, but also of the atomic gas out of which they form.

November 6, 2009
"The Complete History of the Universe, Abridged " by Eugene Lim, Postdoctoral Research Scientist, Columbia University, Astronomy & Astrophysics
3:10 pm
Franklin Miller, Jr. Lecture Hall (RBH 109)
Abstract: In the past decade, cosmology has advanced from being a theory-heavy-data-light subject to one that is now driven by data. While some of the consequences of this fact are rather embarrassing to theorists, we are beginning to harness the power of large observational datasets from space-borne and ground-borne experiments to test our theories. In this talk, I will give a brief overview of what we know about the Universe, and then focus on how we can go about observationally testing one of the pillars of cosmology today: cosmic inflation. Reception to follow.

November 13, 2009
"A Brief Introduction to Pseudosparks " Senior Talk by Kasey Kelly, '11
3:10 pm
Franklin Miller, Jr. Lecture Hall (RBH 109)
Abstract: Plasmas are conductive and respond to electric and magnetic fields which makes them appropriate for many industrial uses. In industrial plasma engineering, a commonly used switch is a low pressure, fast discharge called the pseudospark. The pseudospark's unique breakdown characteristics make it ideal for applications calling for switching large currents in short amounts of time. In this talk, I will review the basics of pseudospark theory and give an overview of the research I did on two different pseudospark applications for use in a particle accelerator. Reception to follow.

December 4, 2009
"Quantum Dynamics of Nonlinear Oscillators," Senior Exercise Talk by Betsy Segelken, '10
3:10 pm
Franklin Miller, Jr. Lecture Hall (RBH 109)
Abstract: Motivated by the analogy to Josephson junctions, we studied the dynamics of a damped, driven pendulum in the quantum limit. We model the effects of damping by means of the quantum state diffusion method, in which the Hamiltonian in Schrodinger's equation is augmented by terms constructed from combinations of Lindblad operators. The dynamics were observed by looking at the time dependence of the expectation values of the pendulum's angular momentum and mechanical energy. The next step is to couple two damped, driven quantum pendula and see if the pendula can synchronize and, if so, under what conditions. This would suggest that it is possible to synchronize coupled small area Josephson junctions, which must be treated in the quantum limit. Reception to follow.

December 11, 2009
"Teaching Physics in Sri Lanka" by Dr. Timothy Sullivan, Kenyon College, Physics Department
3:10 pm
Franklin Miller, Jr. Lecture Hall (RBH 109)
Abstract: Professor Sullivan spent eight months teaching physics in Sri Lanka as a Fulbright Scholar last year, and in the course of his travels, he and his wife completed a circumnavigation of the globe. Professor Sullivan will relate his observations of teaching and learning physics in Sri Lanka and Pakistan as well as some anecdotes of living in a different culture. The talk will also include a few photos of their journey to Sri Lanka through China, Vietnam, Cambodia, Singapore, and Malaysia and their journey home by way of India, Jordan, Israel, and the UK. Reception to follow.