College of Arts and Sciences

The last decade has seen a revolution in our understanding of the tiniest fundamental particle, the neutrino. The results of several experiments have shown that neutrinos oscillate and therefore have mass. This opens the door for neutrinos and antineutrinos to interact differently, and this little particle to explain the matter antimatter asymmetry in the universe. The first measurement to explore this possibility is a measurement of the third and smallest mixing angle governing neutrino oscillation q13. The reactor neutrino experiment Double Chooz is coming online now to make this difficult measurement. The physics of neutrino oscillation and reactor neutrino production will be reviewed.

Continue reading… “It’s Chooz Time Folks!” – Michelson Postdoctoral Prize Lecturer Lindley Winslow,

In November 2010, the Large Hadron Collider (LHC) at CERN completed its first physics run of proton-proton collisions at sqrt(s) = 7 TeV. These data, which have been analyzed in recent months, have provided us with our first glimpse of the energy frontier. I will review why particle physicists are so excited about what we might find as we explore this newly accessible regime and present some of the scientific results which have already emerged. There are, however, a number of scenarios of physics beyond the Standard Model which predict new heavy quasi-stable particles at the LHC which could spoil the party;

Continue reading… Exploring the Energy (and Lifetime) Frontiers with the CMS Experiment – Christopher Hill

Continue reading… Financial Mathematics for Physicists – Bryan Lynn

I will review the technical history of nuclear weapons, the U.S.-Soviet nuclear arms race and efforts to control the spread of nuclear weapons after the end of the Cold War. I will then focus on technical issues related to the Comprehensive Nuclear-Test Ban Treaty, which the U.S. has signed, but not yet ratified. Finally, I will describe opportunities for students interested in careers at the intersection of science and public policy, both within the U.S. government and in non-governmental organizations.

Continue reading… The Comprehensive Nuclear-Test Ban Treaty – Rob Nelson

In 1971 Hawking published the Area Theorem, which shows that the area of a black hole either increases or stays the same. Two years later, Bardeen, Carter, and Hawking proved a theorem which relates the changes in the mass of a black hole, to changes in its area. These two results had a striking formal resemblance to the second and first laws of classical thermodynamics respectively. However, since nothing comes out of a black hole, it seemed that a black hole can not radiate and can not have a temperature, and so can not really be a thermodynamic system. Then in 1975,

Continue reading… Black Holes and Thermodynamics – Jennie Traschen

Experiments and observations over the last decade have persuaded cosmologists that (as yet undetected) dark energy is by far the main component of the energy budget of the universe. I review a few simple dark energy models and compare their predictions to observational data, to derive dark energy model-parameter constraints and to test consistency of different data sets. I conclude with a list of open cosmological questions.

Continue reading… Dark Energy: constant or time variable? (… and other open questions) – Bharat Ratra

Three 15-minute talks on the 2010 Nobel prizewinners and their work

Continue reading… The 2010 Nobel (Sciences) Prize-fest – Tim Atherton, Yanming Wang, and Paul Tesar

With the third generation ground-based gamma-ray telescopes delivering over a hundred new TeV emitting objects and with the new Fermi satellite providing greatly improved sensitivity in the GeV energy regime, gamma ray astronomy is entering a golden age. I will first review the basics of ground-based gamma-ray astronomy and the Air Cherenkov Telescope method of detection. I will then describe VERITAS – an array of four gamma ray telescopes located at Mt. Hopkins, Arizona – and some of the recent results from the first few years of the VERITAS observing program, paying attention to the observations of several new TeV emitting active galactic nuclei and the discovery of the starburst galaxy M82 in TeV gamma rays.

Continue reading… The New World of Gamma Ray Astronomy – Lucy Fortson

Lasing materials range from periodic systems such as photonic crystals to partially ordered and disordered dielectric materials that scatter light diffusively. Soft materials, in particular liquid crystals, may be manipulated easily and have interesting optical properties. They are extremely promising for engineering photonic nano- structures, either as stand-alone devices or as part of innovative integrated systems. These applications can range from photonics to the bio-medical arena where miniaturized tunable laser sources may find a vast area of uses, such as optical tweezers, endoscopic sources for cancerous tissues treatment, lab-on-chip and other still yet-to- be-conceived purposes. Here, the investigation of ordered and disordered soft nano-structures to achieve compact,

Continue reading… From Lasing in Soft-Composite Materials to Optical Transparency in Metamaterials – Giuseppe Strangi

One of the longest-standing mysteries of fundamental astrophysics is the origin and nature of the highest energy cosmic rays. These particles are the most energetic in the universe, arriving to the Earth from all directions in outer space. When these particles strike the earth’s atmosphere, they produce extensive air showers made of billions of secondary particles. The Pierre Auger Observatory has been designed and built to directly confront this mystery by making extensive measurements of air showers from these cosmic rays. After several years of operation, results from Auger have revealed key properties of the cosmic rays in terms of their energies,

Continue reading… The Persistent Mystery of the Highest Energy Cosmic Ray – Corbin Covault

I will discuss progress in two ongoing sets of experiments on the packing of macroscopic objects. The first of these is a neglected aspect of the old problem of packing identical spheres. Much attention has recently been paid to packings of frictionless spheres, particularly to the geometry and mechanics of the random close packed state. I will report new results on the opposite limit: that of the loosest mechanically stable packings achievable in systems of frictional spheres. The second class of packing problems I will discuss is the packing of a thin sheet in a volume of much smaller linear dimension.

Continue reading… Two packing problems – Narayanan Menon

Electronics applications such as light emitting devices for lighting and flat panel displays, transistors, solar cells and sensors based on p-conjugated organic materials are presently being developed and have in some cases reached the market. Here is given an overview of the materials properties of p-conjugated molecules, in particular how optical absorption and luminescence as well as the electron- and hole-injection levels can be tailored through organic synthesis. We briefly discuss the strengths and weaknesses of organic electronic and spintronic applications where p-conjugated materials currently are used. The importance of interfaces in organic electronic applications is highlighted as e.g. solar cells,

Continue reading… Pi-conjugated organic materials: properties, applications and the importance of interfaces – Mats Fahlman

In this talk I will present a biophysical perspective that describes the fate of nanoparticles in both the aqueous phase and in living systems. Specifically, I will show the correlations between the physicochemistry of fullerenes and their uptake, translocation, transformation, transport, and biodistribution in mammalian and plant systems, at the molecular, cellular, and whole organism level. In addition to fullerenes and their structural derivatives, I will describe the biological and environmental implications and applications of the condensed matter of carbon nanotubes and the soft matter of dendritic polymers. The main purpose of this talk is to demonstrate the vast opportunities and unique advantages of applying experimental and simulation biophysics and nanoscience to the research field of understanding nanoparticles at large.

Continue reading… A Biophysical Perspective of Understanding Nanoparticles at Large – Pu-Chun Ke

Emulsions, typically droplets of oil in water, are widely used in, e.g. cosmetics, paints, foods and polymer synthesis. The surface of the droplet, where the two liquids meet, is energetically expensive; to make the droplets long lived this energy cost is often reduced by adding a molecular surfactant. The focus of my research is the new physics which emerges when the molecular surfactant is replaced by colloidal particles. Because the particles are mesoscale objects they are extremely strongly trapped at the droplet interface and they also modify the average properties of the individual droplets. I will demonstrate how these characteristics lead to novel composite materials.

Continue reading… Advanced Materials Stabilized by Interfacial Particles – Paul S. Clegg

Chromonic liquid crystals form when molecules aggregate into anisotropic shapes at high enough density to promote orientational order. There is strong evidence that in some systems the aggregates are simple columnar stacks of molecules and that the aggregation process is governed by free energy changes that are independent of the size of the aggregate. Theoretically such systems should not possess a critical concentration or critical temperature for aggregation, and this is confirmed by experimental results. However, there is also excellent evidence that in one system a critical concentration or critical temperature for aggregation occurs. There is also good evidence that the aggregate structure can differ from a simple stack of molecules in several ways.

Continue reading… Aggregating Dyes and Chromonic Liquid Crystals – Peter Collings

Dye doped polymers, which were originally designed for nonlinear-optical applications, combine the good optical quality and processabilty of the host polymer with the optical and electrical properties of the dopant. Combining the nonlinear-optical and photomechanical properties in a single material may lead to utrasmart morphing materials with emergent properties. In this talk, I will discus our research on the mechanisms of of the photomechanical effect in dye-doped liquid crystal elastomers, demonstration of novel devices, and the observation of new phenomena such as self-healing following photodegradation. To conclude, I will speculate on futureque applications of highly integrated utra-smart photomechanical materials.

Continue reading… Smart Polymeric Materials: From Fundamental Science to New Technologies – Mark G. Kuzyk

The South Pole Telescope is dedicated to mapping several thousand square degrees of the southern sky at millimeter wavelengths. Four years into the survey, we are using the data to better understand the formation of large scale structure in the universe, and to constrain the character of the elusive Dark Energy which dominates the energy density of the universe but is (so far) not at all understood. In this talk I will describe the SPT and our recent findings, and discuss how upcoming results and future work will shed further light on the nature of things Dark.

Continue reading… Cosmology with the South Pole Telescope – John Ruhl

Stellar evolution from a protostar to neutron star is of one of the best studied subjects in modern astrophysics. Yet, it appears that there is still a lot to learn about the extreme conditions where the fundamental particle physics meets strong gravity regime. After all of the thermonuclear fuel is spent, and after the supernova explosion, but before the remaining mass crosses its own Schwarzschild radius, the temperature of the central core of the star might become higher than the electroweak symmetry restoration temperature. The source of energy, which can at least temporarily balance gravity, are baryon number violating instanton processes which are basically unsuppressed at temperatures above the electroweak scale.

Continue reading… Electroweak stars: Electroweak Matter Destruction as an Exotic Stellar Engine – Dejan Stokovic

Magnetic resonance imaging (MRI) provides exquisite depiction of anatomy and function without the ionizing radiation found in e.g. CT or PET. However, significant drawbacks still exist. This is primarily due to the limited speed and signal-to-noise ratio (SNR) of MRI, and most important, the fact that these two quantities are linked to each other. Conventionally, as with any linear system, any increase in imaging speed has required a loss in SNR and vice versa. In order to realize any truly dramatic increases in either SNR or imaging time, some way to break this relationship must be found. New developments in the world of information theory,

Continue reading… Rethinking MR: Collecting information instead of images – Mark Griswold

Semiconductivity (SC) and ferromagnetism (FM) are an unlikely couple, each having quite different desires in regard of the electronic band structure (High density of states at the Fermi level for FM, but low or moderate for SC). In the search for materials that make this difficult relationship work, electronic structure theory has played a prominent role, predicting new diluted magnetic semiconductor (DMS) materials, offering explanations and suggesting models for the underlying physical mechanisms. However, treacherous pitfalls need to be avoided along the path leading from a density functional calculation to a realistic model for DMS. In this talk, I will highlight examples how such calculations can produce “false positives”,

Continue reading… The quest for dilute ferromagnetism in semiconductors: Guides and misguides by theory – Stephan Lany

Over the last five years or so, my group has studied the properties of a new family of nitride semiconductors, the II-IV-N2, the compounds, such as ZnGeN2, ZnSiN2. One can view this as a new way to modify the properties of GaN semiconductors. Instead of isovalent substitution of different group III elements, we substitute alternately a group II and IV element, coordinating each N tetrahedrally with two of each. Unlike isovalent substitution, which leads to disordered alloys, this type of substitution leads to well ordered compounds. Another example, of this type of heterovalent substitution is replacing ZnO by LiGaO2. These materials have received relatively little attention so far.

Continue reading… Heterovalent ternary compounds, a new form of semiconductor property engineering: from electronic energy bands to lattice dynamics – Walter Lambrecht

Superconducting circuitry can now be fabricated at the nanoscale, e.g., by depositing suitable materials on to single molecules, such as DNA or carbon nanotubes. I shall discuss various themes that arise when superconductivity is explored in this new regime, including the thermal passage over and quantum tunneling through barriers by the superconducting condensate as a whole, as well as a strange, hormetic effect that magnetism can have on nanoscale superconductors. I shall describe nanoscale superconducting quantum interference devices, which are subtly sensitivity to magnetic fields and patterns of supercurrent — features that hint at uses of superconducting nanocircuitry, e.g., in mapping quantum phase fields and testing for superconducting correlations in novel materials.

Continue reading… Strands of Superconductivity at the Nanoscale – Paul Goldbart

TBA

Continue reading… From quantum mechanics to radiology to business, starting with the basic physics of vascular imaging – Mark Haacke

The surface and interfacial properties of polymers play a key role in many technological applications ranging from telecommunication to biotechnology. Most of the intended applications strongly depend on wetting and adhesion phenomena. Understanding the structure and thermodynamic properties of polymers at interfaces is thus an area of fundamental and current technological interest. Although excellent experimental progress has been made over the years in understanding the molecular structure of polymers in contact with various environments, the quantitative analysis has been more difficult. In the past few years, computer simulations have made significant contributions by providing the details that are lacking in the experimental data.

Continue reading… Morphology and dynamics of polymers at interfaces – Mesfin Tsige

Thermoelectric energy converters are solid state devices that convert thermal to electrical energy, and are used in heat pumps and power generators. They have no moving parts, conveying them the inherent advantages of compactness and robustness that have traditionally been offset by their low efficiency. This changed in the last decade when several classes of materials were developed with double the efficiency of commercial materials. Consequently, the new materials are poised to play a significant role in energy recovery applications from waste heat, and in new efficient air-conditioning schemes. This talk will briefly review the new applications, as well as the recent materials design strategies used.

Continue reading… High-efficiency thermoelectric materials: new design strategies, new applications – Joseph Heremans

The prediction by Slonczewski and Berger that currents in magnetic heterostructures can exert a torque on the magnetization in the structures has lead to intense research over the past decade. This is both because of a new area of fundamental physics made possible by coupling DC currents and spin dynamics, as well as technological applications, such as magnetic random access memories and nano-scale high-frequency oscillators, in spintronics. Magnetic tunnel junctions (MTJs) consist of two magnetic layers separated by an insulator. In such structures, spin torque can induce a range of magnetization dynamics from coherent oscillations to switching and chaotic motion.

Continue reading… Spin torque effects in magnetic tunnel junctions – Olle Heinonen