College of Arts and Sciences

Our knowledge of neutrino physics has undergone dramatic improvement in the last few years. We are now in the position to make confident predictions taking neutrino oscillations into account, opening the possibility to search for truly exotic particle physics within the neutrino sector, and to use neutrinos as reliable probes of astrophysics and cosmology. However, some very fundamental questions about neutrinos remain unanswered, such as whether their masses are of Dirac or Majorana type, or what the absolute neutrino mass scale is (oscillation experiments only reveal information about mass differences). We discuss implications of neutrino mixing for astrophysics and cosmology,

Continue reading… Neutrino Physics and Astrophysics: What we have learned and what we would like to discover – Nicole Bell

Microtubules are self-assembling/self-destructing tubular crystals of the protein tubulin that underpin the structure of most cells. Their dramatic dynamic instability has generated interest among biologists and physicists alike since its discovery in 1984, but still awaits a physical explanation. One reason is that tubulin is not amenable to the powerful expression and mutagenesis techniques of molecular biology. Another is that dynamic instability has no analog among non-biological materials. In this talk I will describe our approach to overcoming these challenges via “synthetic biology”. Briefly, we have developed a set of short sequences of DNA that use Watson-Crick base-pairing to self-assemble into tubular crystals which bear analogy to microtubules.

Continue reading… DNA Microtubules: a physical approach to synthetic biology – Deborah Fygenson

One of the long-standing problems in colloid science is whether there is like-charge attraction or repulsion between colloid particles in confinement and whether there are stable facets and voids in colloidal crystals. Using computer simulations with explicit microions, we show here that colloidal attraction is mediated via space charges opposite in sign to the colloidal charge. The space charging only occurs at low (but finite) added salt concentrations and in a complex geometric environment of the colloids. This implies a novel control over colloidal interactions and transport in charge-patterned microfluidic devices and has relevance for protein aggregation.

Continue reading… Confinement and Salt-Induced Long-Range Attraction in Colloids – Elshad Allahyarov

Recent advances in string theory leads naturally to an inflationary scenario that can be tested via cosmological observations.

Continue reading… String Theory and Cosmology – Henry Tye

The combination of a nematic or cholesteric liquid crystal and a crosslinked polymer network, either an elastomer or a gel, is a classic example of a hyper-complex fluid system. The orientational interaction between polymer chains of the network and the long range ordering of the nematic phase links the two systems together. Elementary consequences of this linkage include the orienting effects of elastic strains of the gel on the nematic director, and conversely, nematic ordering induced strains of the gel network. However, there are surprising emergent properties of this combination of two complex fluid systems. Certain shear deformation modes of the polymer network lose their elastic restoring force,

Continue reading… Nematic Elastomers: Liquid Crystals and Fluid Solids – Robert Meyer

Continue reading… A New Approach to Monte Carlo Methods in Statistical Physics – David Landau

Hydrogen offers a compelling solution to the energy challenges of supply, security, pollution, and climate change. Although today’s technology enables several routes for producing, storing, and using hydrogen, none of them are yet competitive with fossil fuels for cost, performance, or reliability. Dramatic advances in the basic understanding of hydrogen and its interactions with materials are needed to bring a hydrogen economy to practical realization. The current state of hydrogen technology and the research challenges for creating a mature hydrogen economy will be discussed.

Continue reading… The two hydrogen economies – George Crabtree

Continue reading… Green Chemistry – Theory and Practice – Paul Anastas

Through a decade of teaching special relativity to general-audience students, I have evolved a teaching strategy that combines numerical, algebraic, and qualitative reasoning. The course treats only space-time aspects of relativity, with no mention of momentum-energy. The non-science majors taking this course leave with an understanding of relativity that is in some ways demonstrably superior to the understanding shown by physics graduate students.

Continue reading… Relativity as a General Audience Course: The Inventor’s Paradox and the Explainer’s Paradox – Dan Styer

The origin of the highest energy cosmic rays has remained a profoundmystery for decades. Physicists are generally interested in cosmic ray sources as potential “beam generators”, providing a source of particles (including, perhaps, neutrinos) with energies far beyond that which could ever be achieved by particle accelerators on Earth. But arguably even more compelling is the underlying astrophysical mystery as to the nature of the accelerating engines for cosmic rays. Are ultra-high energy cosmic rays accelerated in jets of accreting black holes? Do they derive from relativistic shocks in intergalactic space? Are cosmic rays generated during gamma-rays burst events? Or do cosmic rays result from the decay of semi-stable super-massive particles left over from the Big Bang?

Continue reading… The Origin of Ultra High Energy Cosmic Rays: New Clues from the Pierre Auger Observatory – Corbin Covault

The fascinating advances in single atom/molecule manipulations with the scanning-tunneling-microscope (STM)-tip allow scientists to fabricate artificial atomic scale structures, to study local quantum phenomena or to probe physical and chemical properties of matter at single atom and molecule level. Here, the STM is not only used to image single atoms/molecules but also used to manipulate them. In this talk, our recent results of single atom/molecule manipulation experiments conducted by using a low temperature UHV-STM on metal and semiconductor surfaces will be presented. The presentation will include tunneling spectroscopy and manipulation of single silver atoms and vacancies, molecular wires such as sexi-phenyl,

Continue reading… Single atom and single molecule manipulation with a scanning tunneling microscope – Saw-Wai Hla

Mathematics is an essential element of physics problem solving, but as professionals, we often fail to appreciate exactly what we are doing with it. Math may be the language of science, but math-in-physics is a distinct dialect of that language that requires both more subtlety and more skills than are typically taught in math courses. Research with students in classes ranging from algebra-based physics to graduate quantum mechanics indicates that (1) we sometimes don’t appreciate the skills students need to solve theÊproblems we assign, and (2) students problems are sometimes with their expectations about what they are supposed to be doing rather than with their math skills.

Continue reading… Problem Solving and the Use of Math in Physics Courses – Joe Redish

In nature there are many systems that exhibit some form of self-organization. Among these are forest fires, earthquakes, sandpiles, maybe sunspots and even life itself. Investigations into the similarity of the dynamics of such systems have been undertaken by using simple cellular automata models. These models have produced some important insight into the dynamics of such systems. Recently a Self-Organized Criticality (SOC) model for turbulent transport in magnetically confined plasmas has been proposed in order to explain some of the observed features of the transport dynamics in these plasmas. This model is based on the dynamics of a sandpile and has among others,

Continue reading… Plasmas as a Prototypical Complex System: Self-Organized Criticality as a Paradigm for Plasma Transport – David Newman

For twenty or more years, it has been possible to perform computations of material-specific ground state properties of solids, liquids, and molecules which agree very well with experiments. These calculations make use of theories in which the many-electron problem is replaced with an effective one-particle (mean field) problem. In the last decade it has become possible to perform calculations of low-lying excited states relevant for the accurate computation of various spectra such as photoemission and optical absorption. The theories underlying these computations are based on perturbation theory (often low order) in the screened electron-electron interaction, and seem to work very well for band insulators and metals.

Continue reading… The calculation of electronic excitations in condensed matter – Lorin Benedict

Abstract: One-dimensional conductors are the wires that will connect the circuits of tomorrowÕs nanoworld, so it is important to characterize their possible conducting phases. We study a novel one-dimensional wire state which arises at the corner of two quantum Hall systems joined at a 90¡ angle, and observe both metallic,Êcritical,Êand insulating 1D behavior. Such non-planar confinement structures are unconventional for the quantum Hall effect and reveal the first observation of a macroscopic one- dimensional state whose conductance increases with decreasing temperature. This system can map out generic properties of one-dimensional disordered conductors since the metallic, critical, or insulating character is tunable with an external parameter,

Continue reading… Bending the quantum Hall effect: Novel one-dimensional metallic and insulating states – Matthew Grayson

In the short duration of six months, one week, and two days, Einstein, in 1905, wrote five papers that stand today at the bedrock of physics. In the context of 1905, only one of these papers was revolutionary. This paper, on the nature of light, made him the father of quantum physics. In the other four papers, Einstein clearly eschewed trivialities as he demonstrated the reality of atoms, established the dimensions of atoms, put the laws of thermodynamics on a new footing, established the validity of the kinetic theory, enhanced the significance of the speed of light, and purged the basic concepts of space,

Continue reading… Einstein 1905: The Standard of Greatness – John Rigden

With a reported 60 million scans made each year and the frequent news articles on what we are learning about our brain and how we think, magnetic resonance imaging (MRI) has become a major clinical and research phenomenon. We hope to discuss 1) the basic role of nuclei in generating pictures, 2) how to win and lose a Nobel Prize, 3) why MRI now is so important in the neuroscience world, 4) why we avoid the word “nuclear,” 5) why it would be marvelous if we could image you inside a very cold refrigerator, 6) a new lie detector and why someday we won’t need to give any more classroom exams.

Continue reading… 2005 Robert Cherry Teaching Award Finalist Lecture: A Simple View of MRI and Its Rich View of Us – Robert Brown

Most condensed matter is riddled with defects that interrupt long-range order. Your house key, for instance, contains a network of grain boundaries and dislocations without which it would be too soft to hold its shape. Microstructure, the spatial arrangement of structural defects, both controls mechanical response and strongly affects transport properties. Understanding microstructure’s formation and evolution is a central goal of materials science research. Defect-rich structures represent metastable states in most materials, and a sample will relax toward more complete long-range order when annealed. But curiously, there are many soft materials in which a defect-rich structure persists even in thermal equilibrium.

Continue reading… The Origins of Microstructure: Dynamics and Patterning of Topological Defects in Soft and Hard Condensed Matter – Robin Selinger

Call it hubris or call it hubris squared, but somebody had to tackle it in this, the centenary of Albert Einstein’s “Annus Mirabilis” — “Miraculous Year” in Latin — and so I, once a physicist of sorts, and now a cognitive scientist fascinated by how people think, and in particular by the universality of analogy-making in human thinking, ranging from the most modest to the most exalted acts of cognition, inevitably found myself turning my metaphorical gaze to the above-mentioned thinker par excellence and reading his own papers as well as books and papers about him, in which, somewhat to my surprise and certainly to my deep gratification,

Continue reading… A Pocket-Sized Telling of the Genesis of the Greatest Ideas of the Greatest Thinker of All Time OR How Analogy Showed Einstein the Light, and How Light Showed Einstein the Universe – Douglas Hofstadter

Continue reading… High Temperatures Superconductors: Recent Progress and Open Questions – Nandini Trivedi