With the discovery of massive neutrinos there has been a lot of speculation about what one can learn from their mixing: from their own nature, to CP violation, to even CPT violation. This colloquium will trace the development of the field, from the key experimental results, to where we stand today, and ideas about how to proceed.

The Belle experiment at KEKB has recently announced several new and exciting results in the ongoing study of CP nonconservation and other beauty-quark related physics. I will describe some of these results and their implications vis a vis the Standard Model of particle physics.

In this talk I will demonstrate, in an audience-friendly manner, that the basic structure of standard quantum mechanics can be derived from two compatible postulates:

I will then show that there exists a very natural way of going beyond the usual structure which turns the fundamental ingredients of ordinary quantum mechanics into dynamical entities. This, I will argue, provides missing conceptual ingredient in all current attempts to formulate a consistent quantum theory of gravity.

This decay has a branching ratio of about 3×10^-11, but is extremely sensitive to direct CP violation and thus will provide a very stringent test of the Standard Model. CP violation is needed to explain why we are here, why primordial matter remains and antimatter is gone. The CP violating reactions in the early universe that are responsible for this may show up in this experiment. We are at the beginning and this is a wonderful opportunity for a student interested in experimental particle physics.

The phase transition temperature for Bose-Einstein Condensation of a three-dimensional ideal gas of bosons at fixed density is something that every physicist learns to calculate in graduate school, if not before. Amusingly, the first correction to that result, from arbitrarily weak interactions, is sufficiently challenging that only now is there beginning to appear some theoretical agreement on its magnitude, roughly 80 years after Einstein computed the ideal gas result.

We live in a vast, old, but nearly wrinkle-free Universe. One of the greatest challenges in modern physics is explaining its origin and properties. We will discuss the conceptual advances in cosmology and show how our understanding of the Universe has been vastly improved from inputs of particle physics and observations. These achievements reaffirm our belief that the Universe can be rationally described by fundamental physics, and provide a new laboratory where we can test physical theories.

I will discuss qualitatively some of non-perturbative aspects of the theory, and compare theories in different dimensions.

Proteins are exponentially unlikely macromolecules that have resulted from evolution, and they are delicately balanced between stability (to maintain their three-dimensional structure) and flexibility (for biological function). Constraint theory and rigidity percolation are mathematical techniques that have been successful in the analysis of bonding networks in disordered solids. Constraint theory can be used to identify the flexible regions in proteins. With these flexible regions as input, the protein's atoms can then be moved in ways consistent with the constraints. Movies will be presented that show the diffusive motion of proteins. When proteins unfold, the rigid core is first gradually weakened. It then breaks into a few fragments in a first-order-like phase transition. We will show that all proteins behave in this universal manner and that the protein's mean atomic-coordination number plays the role of a reaction coordinate as it goes from rigid (folded) to unfolded (flexible). Comparisons will be made with measured transition states and folding cores. [A recent reference on our work: A.J. Rader, B.M. Hespenheide, L.A. Kuhn, and M.F. Thorpe, Proc. Natl. Academy of Sciences 99, 3540 (2002).]

Mike Thorpe is Professor of Physics, Chemistry, and Biochemistry at Arizona State University. He earned his Ph.D. at Oxford and was on the faculty at Yale before spending many years at Michigan State, where he was named Univ. Distinguished Professor. He joined the ASU faculty in June 2003.

I present numerical and theoretical results for models of magnetization switching and hysteresis in nanoparticles and ultrathin films. The models and computational methods include kinetic Ising models of highly anisotropic magnets which are simulated by kinetic Monte Carlo methods, and micromagnetics models of continuum-spin systems that are studied by finite-temperature Langevin simulations. The theoretical analysis builds on the fact that a magnetic particle that is magnetized in a direction antiparallel to the applied field is in a metastable state, analogous to a supercooled fluid. Nucleation theory is therefore used to analyze magnetization reversal as the decay of this metastable phase to equilibrium. Simulation results are presented for kinetic Monte Carlo simulations of simple Ising models, pure as well as with impurities and surfaces, and for finite-temperature micromagnetics simulations of nanometer-sized iron pillars.

The ability to control the structure, composition, and thickness of matter on the nanometer length scale has recently led to the emergence of a new interdisciplinary field - Nanotechnology. A particularly important approach for nanoscale control, especially for organic materials, is known as self-assembly. This refers to the spontaneous formation of organized structures due to specific interactions that into the material building-blocks. Using a very simple, yet powerful, self-assembly approach based on electrostatic attraction of oppositely-charged species, one can rapidly grow multilayer structures with controlled monolayer thickness in the range 0.3 to >10 nm. The ionically self-assembled multilayer (ISAM) fabrication method is applicable to a vast array of multivalent species including polymers, fullerenes, dyes, proteins, and nanoparticles and to numerous substrate materials. We have shown that the internal electric fields inherent in the ISAM fabrication process can yield highly polar organic films with large second order nonlinear optical susceptibilities and excellent temporal and thermal stability. We have also recently developed a novel approach to control the compositions of the donor and acceptor species in organic solar cells containing semiconducting polymers and fullerenes. The resulting concentration gradients provide the optimal morphology for the competing interests of the charge transfer and charge transport processes.

Observations over the past century have enabled astronomers to pin down a specific quantitative model of the evolution of the universe. Recent observations in particular have led researchers to the conclusion that the expansion of the universe is undergoing acceleration, whereas deceleration would be expected if ordinary matter dominated the contents of the universe. This surprising result implies that about 73% of the energy in the universe is in a form we know almost nothing about, beyond the name we have placed on it - "dark energy". Another 23% is "dark matter", known only from its attractive gravitational effects. Only about 4% of the content of our universe is ordinary matter, the stuff in the periodic table of the elements. Interestingly, the basic story behind these conclusions is understandable using very simple physics. In this talk I explain how this picture of our universe has emerged.

We are rarely explicit about what we want our students to learn in introductory college or university physics. We often say we want them to learn problem solving, but we usually have in mind complex, expert problem solving skills. In practice, we usually test for algorithmic problem solving and pattern matching skills - something quite different. I refer to this gap between what we want and what we do as representing a "hidden curriculum." At the University of Maryland, the Physics Education Research Group has been exploring some of the components of the hidden curriculum - concept learning and cognitive attitudes towards physics. Our results, and the results of other physics education research groups, are beginning to clarify the nature of the difficulties with traditional teaching methods and to demonstrate some effective ways to improve our instruction.

• Teaching physics: figuring out what works, Edward F. Redish and Richard N. Steinberg, Physics Today 52, 24-30 (January, 1999).
• Teaching Physics with the Physics Suite, Edward F. Redish (John Wiley & Sons, 2003).
• A Theoretical Framework for Physics Education Research: Modeling student thinking, Edward F. Redish, to be published in Proceedings of the Varenna Summer School, Enrico Fermi Course CLVI, (Italian Physical Society, 2004).

Wigner's 1932 quasi-probability Distribution Function in phase-space is a special (Weyl) representation of the density matrix. It has been useful in describing quantum flows in: semiclassical limits; quantum optics; nuclear physics; decoherence (eg, quantum computing); quantum chaos; Welcher Weg puzzles. It is also of importance in signal processing.

Nevertheless, a remarkable aspect of its internal logic, pioneered by the late J. Moyal, has only emerged in the last quarter-century: It furnishes a third, alternate, formulation of Quantum Mechanics, independent of the conventional Hilbert Space, or Path Integral formulations, and perhaps more intuitive. It is logically complete and self-standing, and acommodates the uncertainty principle in an unexpected manner. Simple illustrations of this fact will be detailed.

For more than thirty years we have known that quarks are the building blocks of nuclear matter. However, quarks have never been observed in isolation but only in combinations with other quarks. Until recently all experimental evidence has shown that, of the many ways that quarks can be grouped to form normal matter, only two combinations have been observed in nature. Mesons are built out of quark and anti-quark pairs, and baryons have a 3-quark configuration. Recent experiments have reported evidence for new states of matter composed of at least 4 quarks and 1 anti-quark. We will review the experimental evidence for these new states, concentrating on data taken with the CLAS detector at JLab which confirms the observation of a narrow state which is about 60% heavier than the proton.

Neutrinos are among the most abundant particles in the universe. In the past few years, we have found compelling evidence that they 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.

Recent developments of materials and devices with critical length scales in the nanometer range have created a need for a more complete understanding of heat transport at the nanoscale. As the size of a structure decreases, its surface area to volume ratio increases and the effects of boundaries and interfaces become increasingly significant. Furthermore, as the critical feature size approaches the mean free path of the energy carriers, other interesting confinement effects become possible as well. In this talk I will discuss some of the latest developments in the area of nanoscale thermal transport while highlighting my own work and I will give a brief summary of the current status of the field. In particular I will talk about heat transport across solid-solid and solid-liquid interfaces, as well as conduction through superlattices, nanotubes and nanowires. Additionally, I will discuss advances in experimental techniques including thermal conductivity imaging at the microscale using time-domain thermoreflectance, scanning thermal microscopy, the 3ω method, and microfabricated structures for thermal property measurements of individual nanowires and nanotubes. Finally, I will talk about a few applications in areas such as thermoelectric devices, infrared imaging, and data storage where a better understanding of nanoscale thermal transport could lead to significant advances.

Bacteria are exquisitely functional micromachines that self-assemble complex structures from molecular building blocks in the face of severe shot-noise due to the small number of molecules involved. For example, E. coli bacteria locate their division midplane through an oscillation of several thousand Min proteins from end to end of the 2 micron bacterium, with a period of about one minute. I will show how this oscillation can be described by a model that only includes diffusion and adhesion/release from the bacterial inner membrane. While oscillations can persist for many fewer molecules than are involved in wild-type bacteria, but we show that significant number of errors would be expected. E. coli appear to express sufficient copies of proteins to minimize division errors.

Earlier puzzles in theoretical physics that were understood, taught us a great deal about the laws of nature. The present challenges are bound to tell us more, as we work to meet them.