Physics Colloquium
University of Illinois at Urbana-Champaign

Abstracts

Dr. Thomas J Bowles


Los Alamos National Laboratory

Solar Neutrinos and New Physics - A New Landscape After SNO

For more than 20 years all measurements have shown a significant deficit of the flux of solar neutrinos compared to that predicted by the Standard Solar Models. The recent results from the Sudbury Neutrino Observatory (SNO) provide compelling evidence for neutrino oscillations as the explanation of the observed deficit. A review of the existing solar neutrino data and the current status and plans for SNO will be presented, along with a discussion of the implications for future directions.

Assist. Prof. Ali Yazdani


University of Illinois at Urbana/Champaign Department of Physics

Fine-Tuning Electronic States in Carbon Nanotubes

The discovery of carbon nanotubes has inspired remarkable advances in science and engineering at the nanometer scale. I will describe experiments that demonstrate a powerful approach to control the electronic states in carbon nanotubes. The self-assembly of molecules inside the hollow cores of these tubes is exploited to create a new class of nanotube materials, the properties of which are examined using state-of-the-art scanning tunneling microscopy techniques. The electronic states of composite nanotube-based materials are shown to depend on the interaction between one-dimensional states of carbon nanotubes and the localized orbitals of encapsulated molecules. Such fine-tuning of nanotubes' electronic states has potential applications for exploring the physics of one-dimensional systems, as well as making electronic devices based on these molecules.

Prof. Stephen H. Schneider


Stanford University Institute for International Studies

Is Climate Change Too Uncertain for Policy

Uncertainties in human induced climate change have spurred a serious policy debate. Many components are well established, however, and a number of win-win opportunities exist for energy planning. Balancing cost-effectiveness, environmental protection and equity in the distribution of costs and benefits presents a major challenge to planetary-scale management.

Prof. Kenneth Laws


Dickinson College Department of Physics and Astronomy

The Physics of Dance

Physics and dance represent remarkably complementary approaches to human body movement - the scientific approach of classical mechanics, and the aesthetic approach of the popular art form of dance. Kenneth Laws, a professor of physics and amateur dancer explores the interplay between natural law and the art (and illusions) of dance. He is the author of The Physics of Dance and Physics as well as other books on the subject.

Prof. Louis Bloomfield


University of Virginia Department of Physics

Physics for the Rest of Us: Examining the Physics of Everyday Life

The world is full of bright people who are interested in things other than physics. Though time, experience, and social pressures have led them to thinking that they "can't do science," they remain curious about how things work. If you give them half a chance and let them ask about their world and what makes it tick, they suddenly find that physics is fun, valuable, and within their reach. This talk will examine uses of case-study approaches to teach physics, both in the classroom and informally, via the web or otherwise

Dr. Geoffrey West


Los Alamos National Lab/ Santa Fe Institute

The Origin of Universal Scaling in Biology from Molecules & Cells to Whales & Ecosystems

Life is the most complex physical system in the Universe manifesting an extraordinary diversity of form and function over an enormous scale ranging from the largest animals and plants to the smallest microbes. Yet, many of its most fundamental and complex phenomena scale with size in a surprisingly simple fashion. For example, metabolic rate (the power needed to sustain life) scales as the 3/4-power of mass over 27 orders of magnitude ranging from molecular and intra-cellular levels up to the largest animals and plants. Similarly, time-scales (such as lifespan and heart-rate) and sizes (such as tree height, genome length, or the density of mitochondria) change with size with exponents which are typically simple powers of 1/4. The universality and simplicity of these scaling relationships strongly suggest that fundamental universal principles underly much of the generic structure, function and organisation of many, and maybe all, biological phenomena. We have recently proposed that these principles are based on the observation that life at all scales is sustained, and ultimately constrained, by space-filling, fractal-like hierarchical branching networks (both real and virtual) which are optimised by the forces of natural selection.Quantitative analyses of the cardiovascular, respiratory and plant vascular systems will be presented as explicit examples. It will be shown how scaling universality can be related to an effective additional fourth spatial dimension of life. Extensions to growth, aging and mortality, ecosystems and the nature of evolution, including thermodynamic considerations and the concept of a universal molecular clock, will be discussed.

Prof. W. E. Moerner


Stanford University Department of Chemistry

Emerging Frontiers in Single-Molecule Spectroscopy

The past dozen years have witnessed a great increase in interest in optical studies of single molecules in complex environments[1]. Single molecules have been used to explore heterogeneity, kinetics, local orientations, energy transfer, and the behavior of single quantum systems in fields ranging from biophysics, to quantum optics, and to materials science. Recently, some groups have begun to explore the behavior of individual molecules in living cells. In collaboration with the McConnell laboratory, we have completed a detailed study of the diffusion of single copies of major histocompatibility complexes of type II (MHCII) in the membranes of CHO cells[2]. The results from this study bear on fundamental properties of the cell membrane, in particular on the presence of significant confinement restricting the motion of the MHCII transmembrane proteins. In the area of materials science, by embedding a fluorophore directly in a polymer backbone, we are able to directly sense orientational changes of a polymer chain without recourse to host-guest techniques[3]. Finally, we have recently discovered a new class of molecules amenable to single-molecule imaging in polymeric hosts, with potential for use in biological environments. The advantages and disadvantages of this new class of single fluorophores will be discussed. [1] W. E. Moerner, "A Dozen Years of Single-Molecule Spectroscopy in Physics, Chemistry, and Biophysics, J. Phys. Chem. B 106, 910-927 (2002). [2] M. Vrljic, S. Y. Nishimura, S. Brasselet, W. E. Moerner, and H. M. McConnell, "Translational Diffusion of Individual Class II MHC Membrane Proteins in Cells," appearing in Biophys. J. (2002). [3] N. B. Bowden, K. A. Willets, W. Wiyatno, W. E. Moerner, and R. M. Waymouth, "The Synthesis of Fluorescently-Labeled Polymers and Their Use in Single-Molecule Imaging," appearing in Macromolecules (2002).

Dr. John Martinis


NIST

Rabi Oscillations in a Large Josephson Junction Qubit

The Josephson junction is an ideal solid-state system for building electrical "atoms" which can function as quantum bits for a quantum computer. I will discuss recent experimental work based on qubits made from large area (10um by 10um) current-biased Josephson junctions. We calculate coherence times longer than 1-10 us should be possible based on a 2-junction SQUID circuit that isolates the qubit from dissipation of the leads. I will discuss recent measurements on a single qubit that shows Rabi oscillations and fidelity of state preparation and measurement of 85%. The construction of a quantum computer circuit with 10-100 qubits might be reasonably straightforward because its fabrication would be based on an existing optical-lithography process.

Prof. Matthew Fisher


University of California at Santa Barbara Institute for Theoretical Physics

Cuprates Amiss: Sublime simplicity or a matted mess?

Theoretical approaches to the cuprate superconductors broadly fall into two classes - one a force-fitting into the standard framework, and the other a quest for qualitative novelty. This talk will be firmly rooted in the latter. I will describe several exotic new quantum phases of 2d correlated electrons, and discuss their promise as candidate phases underlying the strange cuprate normal state behavior.

Prof. Malvin Kalos


Lawrence Livermore National Lab

Is Fermion Monte Carlo Hard?

The fact the the Schroedinger Equation in imaginary time is a diffusion equation makes it possible to carry out exact numerical calculations of many-boson systems. Many-fermion systems seem to be more difficult. We will discuss qualitatively the reasons for this. Simple modifications of diffusion Monte Carlo permit many-fermion systems to be calculated: (a) Random walkers carry signs. (b) Distinct guiding functions are used for walkers of different signs. (c) Walkers are always treated in pairs. (d) The Gaussians that generate diffusion for pairs of opposite walkers are correlated in such a way that the walkers drift towards each other. (e) Opposite walkers in a pair cancel when close.

Dr. Boris Kayser


Fermilab

The Neutrino World: Present and Future

Neutrinos are among the most abundant particles in the universe. In the past few years, we have found compelling evidence that the neutrinos made in the earth's atmosphere by cosmic rays, and those made in the sun, can morph from one "flavor" to another. This flavor change implies that neutrinos have nonzero masses, and opens a whole new world for us to explore. In this talk, we will explain what has been learned about the neutrinos so far, identify some of the major open questions, and discuss future experiments that can help us to answer them.

Prof. Rainer Weiss


M.I.T. LIGO Scientific Collaboration

Interferometric Detection of Gravitational Waves - The Status of the LIGO (Laser Interferometer Gravitational-wave Observatory)

After a brief description of the basic concepts of gravitational wave detection and an even briefer overview of possible astrophysical sources, the talk will concentrate on the current performance of the instruments and the state of the data analysis. If time permits, future improvements to LIGO and the prospects for a space based low frequency detector will be presented.

Prof. David Hertzog


University of Illinois at Urbana-Champaign Department of Physics

Has the muon magnetism revealed a crack in the standard model?

Our measurement of the muon's anomalous magnetic moment at Brookhaven Lab has now reached a sub-ppm (part per million) precision and, some would say, it disagrees with theory. If true, it's quite exciting as the implication suggests that the standard model is incomplete. Many believe this to be the case and have suggested that supersymmetry is a natural extension, and, it would perfectly describe the current difference between our measurement and theory. What our experiment is about, why the theory is controversial at present, and speculations for the future sums up the outline of my talk. I intend to pitch it for the non-specialist.

Prof . Robert Jaffe


MIT

The Casimir Effect: Theory and Practice

Over half a century ago, Hendryk Casimir predicted the existence of a force between grounded conducting plates due to their effect on the vacuum fluctuations of the electromagnetic field. Casimir's force depends only on Planck's constant, the speed of light, and the distance between the plates. Recently, new experimental methods have confirmed Casimir's prediction with great precision. The "Casimir Effect" has been interpreted as direct evidence for quantum effects in the vacuum and applied to everything from micromachinery to the cosmological constant. I will review the origins and critique the interpretation of the Casimir Effect, review the stunning experimental progress of recent years, and describe applications of Casimir's ideas to problems in particle physics and beyond.

Asst. Prof. David Goldhaber-Gordon


Stanford University Physics Department

A Survey of the Kondo Effect in Mesoscopic Systems

The Kondo effect --- the interaction of a magnetic impurity with a sea of conduction electrons --- has long been a centerpiece of condensed-matter theory and experiment. Its study is now experiencing a resurgence, thanks to the experimental realization of magnetic impurities in mesoscopic systems. These experimental systems fall into two categories: magnetic impurity atoms in submicron metal wires or islands, and "artificial magnetic impurity atoms" --- submicron few-electron droplets with nonzero net spin --- in semiconductors. I will mention some exemplary achievements in each category of system, dwelling especially on the latter category. An artificial impurity in a semiconductor is fully tunable: its energy levels, coupling to the outside world, even total occupancy can be altered by application of a gate voltage. This unique flexibility has enabled both quantitative verification of decades-old theories and observation of remarkable and quite unanticipated phenomena. Finally, I will discuss prospects for more exotic magnetic systems that may be constructed in semiconductors using these same techniques. These new model systems are particularly exciting, as they have no clear analogues in nature.

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