Fall 2013 Colloquium Series
Colloquia are at 4pm, Thursdays, in 100 Willamette Hall and are preceded by coffee, tea, and cookies at 3:40 in the Willamette Atrium.
The organizer of the Spring Term Colloquia is: Dietrich Belitz
State of the Department & Developments at LIGO
Precambrian Life on Land
Before the evolution of land plants, the land has traditionally been considered as barren as the surface of Mars. New studies of fossil soils in Precambrian rocks not only reveal surprisingly clayey and deeply weathered land surfaces, but also a variety of terrestrial creatures well back in geological time. Some of these, such as the recently described problematicum Diskagma known to be as old as 2200 million years, show a surprising degree of complexity comparable with that of organisms with nucleated cells. Furthermore, comparable living creatures, such as Geosiphon, are a symbiosis of fungus and photosynthetic cyanobacteria, which may have been instrumental in transformation of the atmosphere during the Great Oxidation Event of 2300-2200 Million years ago.
University of British Columbia
Ettore Majorana and his strange particles
In 1937 Italian physicist Ettore Majorana predicted the existence of
strange fermionic particles that are their own antiparticles. It is
possible that neutrinos realize such Majorana fermions but 75 years
after the historical prediction the evidence remains inconclusive. In
this talk I will describe recent efforts to engineer and observe
Majorana fermions in solid state systems which appear to be very close
to fruition. Majorana fermions have been theoretically predicted to
occur in a class of systems called topological superconductors.
Although such systems do not seem to exist in nature they can be
engineered by combining other ingredients such as the ordinary
superconductors and semiconductors with strong spin-orbit coupling or
topological insulators. Signatures consistent with Majorana fermions
have already been reported in such hybrid devices and the race is on
for the first conclusive experimental observation. I will explain the
intriguing physics behind these solid-state realizations of Majorana
fermions and discuss their significance for future technologies.
Active Learning of Introductory Optics: Strategies for the U.S. & the Developing World
Widespread physics education research has shown that most introductory physics students have difficulty learning essential optics concepts—even in the best of traditional courses, and that a well-designed active learning approach can remedy this. This talk will describe strategies for promoting active involvement of students in their learning. The focus will be on Interactive Lecture Demonstrations (ILDs) (1,2)—a learning strategy for large (and small) lectures, and on RealTime Physics laboratories (3,4). These materials have been used successfully in introductory, college-level physics courses. Research on the effectiveness of these learning strategies will also be presented.
These active learning strategies have also been used by the author in a series of teacher enhancement workshops in developing countries, Active Learning in Optics and Photonics (ALOP) (5,6). These workshops—sponsored by UNESCO, ICTP, SPIE, OSA and US NAS—introduce college-level and secondary teachers to active learning. Details on the ALOP project will be presented.
1. David R. Sokoloff and Ronald K. Thornton, Interactive Lecture Demonstrations (Hoboken, NJ, John Wiley and Sons, 2004).
2. David R. Sokoloff, “Using Interactive Lecture Demonstrations to Create an Active Learning Environment,”The Physics Teacher 35: 6, 340 (1997).
3. David R. Sokoloff, Ronald K. Thornton and Priscilla W. Laws, “RealTime Physics: Active Learning Labs Transforming the Introductory Laboratory,” Eur. J. of Phys., 28 (2007), S83-S94.
4. David R. Sokoloff, RealTime Physics Module 4: Light and Optics, 3rd Ed., (Hoboken, NJ, John Wiley and Sons, 2012).
5. Active Learning in Optics and Photonics Training Manual, David R. Sokoloff, ed., (Paris, UNESCO, 2006).
6. “A Lens into the World,” AAPT Iteractions, April, 2008, pp. 20-23.
University of Chicago
Unraveling knotted fields
To tie a shoelace into a knot is a relatively simple affair. Tying a knot in a field is a different story, because the whole of space must be filled in a way that matches the knot being tied at the core. The possibility of such localized knottedness in a space-filling field has fascinated physicists and mathematicians ever since Kelvin’s ‘vortex atom’ hypothesis, in which the atoms of the periodic table were hypothesized to correspond to closed vortex loops of different knot types. Perhaps the most intriguing physical manifestation of the interplay between knots and fields is the existence of knotted dynamical excitations. I will discuss some remarkably intricate and stable topological structures that can exist in light fields whose hydrodynamic-like evolution is governed entirely by the geometric structure of the field. I will then turn to experimental hydrodynamics: how to make knotted vortex loop configurations in fluids and how they evolve once made.
Department of Physics, University of Oregon
Making a Two-Dimensional Thermal Ideal Gas by Shaking Your Breakfast
Active, driven systems as diverse as flocking starlings, swarming bacteria, and vibrating granular beds are by definition non-equilibrium, lacking a well defined thermal temperature that characterizes their dynamics. Because of this, the creation of a coherent non-equilibrium statistical mechanics has proven elusive, and it remains unclear whether, for any non-equilibrium system, a meaningful effective temperature exists. We have constructed an active, driven system of chaotic faraday waves whose statistical mechanics, we find, are surprisingly simple, mimicking those of a thermal ideal gas. We use real-time tracking of a single floating probe, energy equipartition, and the Stokes-Einstein relation to define and measure a pseudotemperature, diffusion constant, and coefficient of viscous friction for a test particle in this pseudothermal gas. Because of its simplicity this system serves as a starting point for direct experimental investigation of non-equilibrium statistical mechanics, much as the ideal gas is the starting point for equilibrium statistical mechanics.
University of Washington
Optically active solid-state defects for photonics-based quantum information applications
Substitutional point defects in crystals have the potential
to offer high optical homogeneity, long spin coherence times, and a
pathway to scalable integration. They are thus promising quantum bit
(qubit) candidates for quantum information processing. The path
toward engineering a suitable defect-based qubit requires (1) the
study of the intrinsic quantum properties of the defect, (2)
engineering the quantum properties for defects suitable for device
integration, and (3) demonstrating device integration. In the first
part of this talk, I report recent results in all three directions
toward realizing a scalable quantum network for the nitrogen-vacancy
defect in diamond. In the second part of the talk I discuss an
alternative system, substitutional shallow impurities in direct
band-gap materials, and present progress toward the isolation of a
single impurity in this novel system.
Kansas State University
The “Standard” Model of Cosmology … and Open Questions
Experiments and observations over the last decade have provided strong support for a “standard” model of cosmology that describes the evolution of the universe from an early epoch of inflation to the complex hierarchy of structure seen today. I review the basic physics, astronomy, and history of ideas on which this model is based. I describe the data which persuade cosmologists that (as yet undetected) dark energy and dark matter are by far the main components of the energy budget of the universe. I conclude with a list of open cosmological questions.