## Colloquium

Junior and senior physics majors attend our biweekly colloquium series, held on Tuesday afternoons at 4:30 pm in Shanahan B460. The talks are open to all students and to the public, and are frequently attended by scientists from the other Claremont Colleges, Cal Poly Pomona, and others. The series features speakers from a broad range of institutions and fields of physics.
 Jan. 31, 2006 Theresa Lynn, Caltech Ultra-High Energy Cosmic Rays: The Mystery of Nature’s Most Powerful Particle Accelerators Stargazing is perhaps one of humanity’s oldest pastimes. As modern astronomers have learned to image the universe in wavelengths across the electromagnetic spectrum, each added picture has answered old questions and uncovered new wonders. In recent years a few observatories have concentrated on very different messengers from the cosmos: subatomic particles called cosmic rays which reach us from as nearby ... Jan. 24, 2006 Martin Madsen, University of Michigan Experimental Quantum Mechanics: Exploring the Quantum World One Atom at a Time "Atoms on a small scale behave like nothing on a large scale, for they satisfy the laws of quantum mechanics," observed Richard Feynman, one of the most brilliant physicists of the 20th century. We can now explore the unusual behavior of a single atom through the combination of an electrical trap and lasers that enable us to isolate and control ... Jan. 17, 2006 Erik Helgren, University of California at Berkeley Optical Properties of Disordered Systems: Terahertz Spectroscopy of Doped Silicon The terahertz (THz) spectral range has been under-utilized in the past both in fundamental research as well as in commercial applications. This spectral range is extremely important for studying condensed matter systems because the photon energy associated with THz frequencies is sub-meV, a typical energy for correlated electron physics; for instance this energy corresponds to the Cooper pair binding energy ... Nov. 28, 2005 Douglas Osheroff, Stanford University The Discovery of Superfluid :mil:\mathrm{He}^3 as Seen Through the Eyes of a Graduate Student It was at the beginning of his fifth year of graduate study that Douglas Osheroff discovered evidence for the existence of two unexpected phase transitions in a mixture of liquid and solid He3, both within three thousandths of a degree of absolute zero. The speaker will describe this event, and give his personal account of the excitement and confusion that ... Nov. 15, 2005 David Awschalom, University of California at Santa Barbara Spintronics, Semiconductors, Molecules, and Quantum Information Processing There is a growing interest in exploiting electronic and nuclear spins in semiconductor nanostructures for the manipulation and storage of information in emergent technologies based upon spintronics and quantum logic. Such schemes offer qualitatively new scientific and technological opportunities by combining elements of standard electronics with spin-dependent interactions between electrons, nuclei, electric and magnetic fields. Here we provide an overview ... Nov. 8, 2005 Nathan Lewis, Caltech Scientific Challenges in Sustainable Energy Technology This presentation will describe and evaluate the challenges, both technical, political, and economic, involved with widespread adoption of renewable energy technologies. First, we estimate the available fossil fuel resources and reserves based on data from the World Energy Assessment and World Energy Council. In conjunction with the current and projected global primary power production rates, we then estimate ... Oct. 25, 2005 Mark Beck, Whitman College Interference, Complementarity, Entanglement and All That Jazz Technology has advanced to the point where it is possible for undergraduates to perform experiments exploring fundamental aspects of quantum mechanics--experiments observing behavior such as wave-particle duality, entanglement, and nonlocality. At Whitman College we are developing a series of such undergraduate laboratories, and I will describe some of these. In one we perform an interference experiment with single photons where ... Oct. 11, 2005 Gabriela Canalizo, University of California at Riverside Galaxy Collisions and the Birth of Quasars Quasars are some of the most powerful objects in the Universe, and their study allows us to probe the early Universe. However, there are still many uncertainties regarding their nature and, in particular, the way in which they are formed. In this talk, I review the role of supermassive black holes, starbursts, and galaxy collisions in the life of quasars. Sept. 27, 2005 Thomas D. Donnelly, Harvey Mudd College Production and Application of an Aerosol of Micron-Scale Particles A device that uses ultrasonic atomization of a liquid to produce an aerosol of micron-scale droplets will be discussed. This device represents a new approach to producing targets relevant to laser-driven fusion studies, and to the relatively untested subfield of nonlinear optics in which wavelength-scale targets are irradiated. The device has also made possible tests of fluid dynamics models in ... Sept. 13, 2005 Kerry Vahala, Caltech :mil:Q > Million Optical Microresonators on Silicon Chips A novel laser processing method has been applied to create optical micro-resonators having Q factors as high as 500 million on silicon wafers. The combination of Ultra-high-Q and small mode volume opens up new applications for wafer based resonators. In this talk I will first review the processing and passive optical properties of these devices and then describe their application ... Sept. 6, 2005 HMC juniors and seniors, Harvey Mudd College What I Did on My Summer Vacation: Off-Campus Summer Research Experiences April 26, 2005 Mark Vagins, University of California at Irvine Close Encounters of the Absurd Kind — A Scientist Looks at UFO’s Look! Up in the sky! It’s a bird? It’s a plane? It’s... a weather balloon? What’s the real deal with America’s ongoing UFO obsession, anyway? What does a professional astrophysicist with an interest in the offbeat think about the whole paranormal scene? Come on an exploration of the claims and issues involved, both from a scientific perspective and through the ... April 19, 2005 Jerry Gollub, Haverford College Chaotic Dynamics of Mixing in Fluids The process by which an impurity is dispersed in a stirred fluid is important for many areas of science and engineering. It can occur as a consequence of turbulence (e.g. in stirring coffee), but mixing also occurs even in some laminar flows that cause nearby fluid elements to separate exponentially in time. This process is sometimes called "chaotic mixing". Until ... April 12, 2005 Wilson Ho, University of California at Irvine Visualization of Quantum Phenomena The unique capabilities of the scanning tunneling microscope (STM) enable new opportunities for the control and investigation of matter and its transformation at the atomic and molecular scales. Some of the problems that are routinely used in the introduction to quantum mechanics, such as the particle tunneling, Brownian motion of molecules, and particle in a one-dimensional box, can be realized ... March 29, 2005 Stanley Klein, University of California at Berkeley New Methods for Imaging Brain Activity in Space and Time When one looks at tiny flashing light, electrical currents are induced in the brain’s cortex and blood flow is altered. The altered blood flow can be measured using functional MRI, giving spatial information of the brain activity, but valuable information about the temporal dynamics is lost due to the sluggish nature of the blood flow. Our focus is on making ...