Physics Colloquium Series
by University of Arizona, Department of Physics
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Description
The UA's Department of Physics has held a Colloquium series for several years. Invited speakers from around the world, as well as scientists from the UA, have presented on their research. Fortunately, the Physics Deptartment has archived these lectures on DVD. We can now bring this outstanding content to students, researchers and others thorugh the UA's iTunes U site.
| Name | Description | Released | Price | ||
|---|---|---|---|---|---|
| 1 | VideoThe Anamalous Magnetic Moment of the Muon | Dr. Blum studies study Quantum Chromodynamics (QCD), the fundamental theory of the strong force. This force binds quarks and gluons together to form protons and neutrons, the fundamental building blocks of matter that make up our world. In principle, QCD describes all of nuclear physics, in the sense that Quantum Electrodynamics describes solid state physics. It is also important to particle physics because most of the particles detected in high-energy collider experiments like those at Fermilab's Tevatron and the soon to be complete Large Hadron Collider at CERN are hadrons, the bound states of quarks and gluons. His lecture was given on September 16, 2011. | 1/24/12 | Free | View In iTunes |
| 2 | VideoDensity Functional Theory: A Great Physics Success Story | Dr. Burke is Professor, Heretical Physical and Computational Chemistry, in UC-Irvine's School of Physical Sciences. His research interests include theoretical chemistry, theoretical physics, math, and computation. His lecture was given on September 2, 2011. | 1/24/12 | Free | View In iTunes |
| 3 | VideoThe IBEX Ribbon: Unexpected Observations of the Interaction of the Heliosphere with the Interstellar Medium | Dr. Jokipii’s research concerns many areas primarily related to plasmas and the transport and acceleration of cosmic rays and energetic particles in the solar wind and in the galaxy. Major current thrusts revolve around work on the Voyager and ACE space missions, for which he and his group are guest investigators, specializing in theoretical interpretaion and modeling of the observations. Specifically, Dr. Jokipii’s group is currently in the midst of an extensive program of theoretical research into shock waves in turbulent astrophysical plasmas. This involves extensive theoretical work and three-dimensional simulations, which are exceedingly demanding of computer resources. His lecture was given on October 29, 2010. | 1/24/12 | Free | View In iTunes |
| 4 | VideoImaging Local Electronic Properties in Graphene | Dr. LeRoy's research interest is using scanning probe microscopy to study interactions in nanostructures. By combining electrical transport measurements with the spatial information from scanning probe microscopy we can gain new insight into the behavior of electrons inside nanostructures. Currently we are investigating interaction effects inside carbon nanotubes using scanning tunneling microscopy. The 1D nature of nanotubes means that Coulomb interactions are very important, leading to effects such as Luttinger Liquid behavior and the Kondo effect. We are also developing new scanning probe microscopy techniques to image electron wavefunctions inside semiconductor quantum dots. This will allow the study of effects such as electron-electron interactions and coherence in these systems. His lecture was given on September 23, 2011. | 1/24/12 | Free | View In iTunes |
| 5 | VideoAxions, the Anthropic Principle, and the Tilted Universe | Axions are particles associated with the Peccei-Quinn mechanism for solving the strong CP problem. They are also interesting candidates for the dark matter. axions with very large decay constant f, say around the GUT scale. Such axions only make sense in an inflationary universe, and then only by having extremely small misalignment between the axion field in the early universe, and the value preferred by QCD. This fine-tuning can be explained invoking the anthropic principle --- it is actually the only case I know of where the anthropic principle really makes sense: one knows the a priori distribution of initial axion field values (a/f being a random angle), and one knows that a Universe without a particularly small range of values for a/f would not support habitable galaxies. With inflation all initial values for a/f occur somewhere, and we live in the only part of the Universe where we could live: where the galaxies are! In my paper with Ann we discuss how there might be observable consequences in this scenario (if we are lucky): the fine tuning of a/f makes us extremely sensitive to spatial variations in a/f, and it turns out the existence of a cosmic axion string as much as 1,000,000 time farther away than our cosmic horizon could be seen as a difference between our peculiar velocities relative to the CMB, and relative to distant type I supernovas. Seeing this effect would be a stunning window into the pre-inflationary Universe! His lecture was given on November 4, 2011. | 1/24/12 | Free | View In iTunes |
| 6 | VideoMCB 315: Key Concepts in Quantitative Biology | Ryan Gutenkunst received his Ph.D. in physics from Cornell University, where he worked with Jim Sethna on unveiling universal “sloppy” parameter sensitivities in systems biology models and on modeling their evolutionary implications. He then did a postdoc with Carlos Bustamante, where he developed ∂a∂i, a powerful method for inferring population histories from genomic data. His second postdoc was with Byron Goldstein at Los Alamos National Lab, where Ryan modeled aspects of immune signaling in mast cells. Ryan joined the faculty in Molecular and Cellular Biology at the University of Arizona in Fall 2010. He is also a member of the BIO5 Institute, the Department of Ecology and Evolutionary Biology, the Program in Applied Mathematics, and the Program in Genetics. He continues to work on both systems biology and population genetics, with a focus on understanding the evolution of biomolecular networks. His lecture was given on October 7, 2011. | 1/23/12 | Free | View In iTunes |
| 7 | VideoNuclear Physics: Bridging from Quarks to the Cosmos | James P. Vary is Professor of Physics and Past Director of the International Institute of Theoretical and Applied Physics (IITAP) at Iowa State University (ISU). He graduated from Boston College (B.S., 1965, Magna Cum Laude), and Yale University (M.S. ,1966 and Ph.D., 1970). He spent two postdoctoral years at MIT's Center for Theoretical Physics and three years at Brookhaven National Laboratory as Assistant then Associate Physicist. In 1975, he joined the faculty at Iowa State University and has fostered the development of a 10-member high-energy nuclear theory group. Professor Vary's research activities span strong interaction physics from ab-initio nuclear structure theory to include fundamental tests of nature's symmetries and to nuclear applications of Quantum Chromodynamics (QCD). Computational physics is another major area of emphasis. His lecture was given on November 18, 2011. | 1/23/12 | Free | View In iTunes |
| 8 | VideoMany-body Effects in the Quasipartilce and Collective Properties of Graphene | Abstract: Graphene is an atom-thick two-dimensional crystal of carbon atoms arranged into a honeycomb lattice. The electron spectrum of graphene is Dirac-like -- linear in momentum. In the intrinsic (undoped) state the density of states at the Fermi level is zero. Nevertheless, the electric conductivity is finite and in the absence of electron correlations can be shown to be of the order of the conductance quantum, 1/(16.4 kOhm). Yet, due to the lack of screening (typical in most metallic systems) the interaction of carriers is strong and there should be little hope that the non-interacting electron gasis a good approximation. Surprisingly, the above value is measured with high precision. How is it possible? We are going to discuss the role played by electron interactions and reconcile it with the measurements of the conductivity. Interactions also lead to a special type of collective oscillations of charge density -- plasmons. Peculiar properties of graphene lead to exotic plasmon waves whose spectrum and direction of propagation allow high degree of control -- "guided" plasmons. Presented Feb. 18, 2011. Dr. Mishchenko is Professor of Physics at the University of Utah's Department of Physics & Astronomy. His research interests: spin-polarized transport in low-dimensional systems, electron-electron interactions in one- and two-dimensional systems, fluctuations in mesoscopic conductors and disordered optical media, superconductivity of cold atom systems. | 6/27/11 | Free | View In iTunes |
| 9 | VideoMuonic Hydrogen Lamb-Shift: Test of QED and Proton Structure | Abstract: The recent very precise extraction of the proton radius from the Lamb shift of muonic hydrogen has created considerable interest. This analysis yields a proton radius smaller than the previous value (extracted mainly from electronic hydrogen) by about four percent or five standard deviations. This implies that either the Rydberg constant has to be shifted by 4.9 standard deviations or that the QED calculations for hydrogen are insufficient. Since the Rydberg constant is extremely well measured, and the QED calculations seem to be highly accurate, the muonic H finding presents a significant puzzle to the entire physics community. We show that off-mass-shell effects arising from the internal structure of the proton provide a new proton polarization mechanism in the Lamb shift, proportional to the lepton mass to the fourth power. This effect is capable of resolving the current puzzle regarding the proton radius. These off-mass-shell effects could be probed in several other experiments. Presented April 22, 2011. | 6/27/11 | Free | View In iTunes |
| 10 | VideoA Stern Dilemma | Abstract: Mr. Stern discussed his decision-making process to enter, and then progress, in a world of engineers while trying to never forget he was educated as an astronomer and physicist. In doing so, asking "Why" may be more important than asking "How". Presented Feb. 25, 2011. Jay Stern, Principal Engineering Fellow and Product Line Chief Engineer at Raytheon Missile Systems | 6/27/11 | Free | View In iTunes |
| 11 | VideoInvestigating Dark Matter with the Fermi Large Area Telescope | Abstract: The Fermi Large Area Telescope (LAT) has been successfully launched from Cape Canaveral on 11 June 2008. It is exploring the gamma ray sky in the energy range from 20 MeV to over 300 GeV with unprecedented sensitivity. One of the most exciting science questions that Fermi LAT will address is the nature of dark matter. Several theoretical models have been proposed that predict the existence of Weakly Interacting Massive Particles (WIMPs) that are excellent dark matter candidates. Fermi LAT investigates the existence of WIMPs indirectly, primarily through their annihilation or decay into photons and into electrons and positrons. I will present recent results on these searches. Presented April 5, 2011. | 6/27/11 | Free | View In iTunes |
| 12 | VideoThe Interface Science of Organic Solar Cells | bstract: Thin film photovoltaic (PV) energy conversion platforms with high efficiencies, low cost, large-area scalability, and long-term stabilities have been identified as possible pathways to the U.S. Department of Energy goal to create multiple photovoltaic platforms with a cost of less than $1/Wp. Organic solar cells (OPVs) are one of the newest entrants to this technology community, and have shown increases in power conversion efficiency up to ca. 8%. These platforms are created from complex material basis sets including: i) active layers based on polymers and small molecules; ii) oxide or polymer/small molecule interlayers; iii) metal or metal oxide electrical contacts and, iv) a variety of glass or plastic substrates and barrier layers. Interlayer films are increasingly added to one or both contacts to: i) make them compatible with organic active layers (e.g. controlling wettability); ii) control energy barriers to charge harvesting of electrons or holes, iii) improve long-term stability, and iv) increase the degree of "charge electivity" of the contact. We'll review some of the issues surrounding how these interlayer materials and contacts function at nanometer length scales, the extent to which they are really charge-selective, and what design criteria are needed at the molecular level to optimize charge harvesting. This area is a research focus for The Center for Interface Science: Solar Electric Materials, a recently formed Energy Frontier Research Center for the U.S. Department of Energy (www.solarinterface.org), whose activities will also be briefly reviewed. Presented Feb. 11, 2011. Dr. Armstrong is Professor of Chemistry/Optical Sciences, Director, DOE-Energy Frontier Research Center for Interface Science: Solar Electric Materials (CIS:SEM), Department of Chemistry & Biochemistry at the UA. His research interests include: Molecular Assemblies/Organic Electroluminescent and Photovoltaic Materials/Interfacial Science/Electrochemistry | 6/27/11 | Free | View In iTunes |
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Quantum Phase Transitions in Hadronic Systems Inside and Outside Neutron Stars (audio only) | Abstract: One of the most active and challenging research thrusts in condensed matter physics seeks an understanding of the unusual, non-Fermi-liquid behavior of strongly correlated electron systems in solids in the vicinity of a quantum critical point associated with a quantum phase transition. A quantum phase transition is distinguished from its classical thermally-driven counterpart in that it takes place at absolute zero under variation of a control parameter such as pressure, doping, or magnetic field. Quantum phase transitions also play prominent roles in strongly-correlated hadronic systems as represented by nuclear matter, neutron-star matter, and expanding supernova ejecta. This theme will be exemplified in (i) the construction of a density-temperature phase diagram of dilute nuclear matter that includes the formation of bound nuclear clusters and the BEC-BCS crossover, (ii) an overview of nucleonic BCS pairing (neutron superfluidity/proton superconductivity) in the inner crust and interior of neutron stars, and (iii) the prospect of a new class of quantum phase transitions occurring not only in terrestrial condensed matter systems, but also in dense neutron-star matter, with implications for fast neutron-star cooling. The new kind of quantum criticality, which involves a symmetry-preserving topological crossover resulting in a rearranged or swollen Fermi surface, has also been explored within the AdS/CFT correspondence. Presented April 29, 2011. | 6/27/11 | Free | View In iTunes |
| 14 | VideoHow Viruses Make New Viruses: A Single-Molecule View | Abstract: Viruses have enormously rich and varied life cycles. Bacterial viruses have a hallowed position in the development of modern biology and recently have become the subject of intensive physical investigation. Using single-molecule techniques, it has become possible to examine viruses both while they package and eject their DNA. This talk will begin with a general introduction to viruses and their life cycles and will then focus on simple physical arguments about the forces that attend viral DNA packaging and ejection, predictions about the ejection process and single-molecule measurements of ejection itself. This topic has lots of fun physical ideas involved with it and we have been doing some interesting theory and experiment. Dr. Phillips is Professor of Biophysics and Biology Option Representative for Biochemistry and Molecular Biophysics (BMB) at Cal Tech. Dr. Phillips research group is part of the departments of Applied Physics (APh), Biochemistry and Molecular Biophysics (BMB) and Mechanical Engineering (ME) at Caltech. His research group is interested in the physical origins of biological function and combine physical models with quantitative experimentation on problems ranging from transcriptional regulation to mechanosensation. His lecture was given on April 8, 2011. | 6/15/11 | Free | View In iTunes |
| 15 | VideoMastering Jets: New Windows Into the Strong Interaction and Beyond | Abstract: The strong interaction is one of the four known fundamental forces of nature and is described by Quantum Chromodynamics (QCD). A key prediction of QCD is that high energy collisions produce streams of collimated particles called jets. The physics of these jets is important for describing high energy experiments, including electron-positron colliders and the LHC proton collider experiment at CERN. In this talk I will describe the physics of jet phenomena and a modern technique for predicting the behavior of QCD jets, called the Soft-Collinear Effective Theory (SCET). SCET provides an efficient framework for describing jets, in much the same way that starting with non-relativistic quantum mechanics provides a simpler and more efficient description of Hydrogen than relying solely on a relativistic framework. Examples will include enhancing our understanding of jet data from past experiments to dramatically improve the measurement of one of the fundamental parameters of nature, the strong interaction coupling constant, and improving our description of jet data now being collected at the LHC, which can play an important role in the hunt being carried out for new particles and forces. Dr. Stewart is Associate Professor of Physics at MIT. Professor Stewart's research interests involve theoretical nuclear and particle physics. In particular, he focuses upon the development and application of effective field theories to further our understanding of Quantum Chromodynamics (QCD). The idea of an effective field theory is to combine the relevant degrees of freedom and symmetries of a system, together with a power counting expansion, into a predictive framework. Different effective theories can be used to describe various limits of QCD in a model independent way. This approach complements lattice QCD since direct numerical simulations are often computationally difficult, whereas lattice simulations of effective theory quantities can be tractable. His lecture was presented March 25, 2011. | 6/15/11 | Free | View In iTunes |
| 16 | VideoParticle Physics and Cosmology in a "Just Right" Universe | Abstract: There are many probes for the nature of the dark matter, from high energy cosmic rays, gamma rays, and nuclear recoils in underground detectors. I describe the recent hints for the nature of the dark matter, and discuss prospects for its discovery. Dr. Zurek works at the interface of particle physics with cosmology and astrophysics. Her work spans both studies of new physics signatures at colliders, as well as astrophysical searches for dark matter (DM) and physics beyond the Standard Model in the neutrino sector. Recently, she has been most active in the study of DM. The presence of DM (five times as prevalent as ordinary matter in the universe) provides strong evidence that there are new particles beyond those in the Standard Model (which describes all currently known particles and interactions). Professor Zurek works on theories of DM and ways that we can detect it in the lab by DM-nucleus interactions, at colliders through high energy collisions, and in the galaxy by DM self-annihilations. His lecture was given on March 4, 2011. | 6/15/11 | Free | View In iTunes |
| 17 | VideoPhysics with Two Time-like Dimensions | Abstract: This talk will explore the properties of physical theories in space-times with two time dimensions. I show that the common arguments used to rule such theories out do not apply if the dynamics associated with the additional time dimension is thermal or chaotic and does not permit long-lived time-like excitations. I discuss several possible realizations of such theories, including holographic representations and the possibility that quantum dynamics emerges as a consequence of a second time dimension. Dr. Mueller is J. B. Duke Professor of Physics at Duke University. Dr. Mueller research currently focuses on nuclear matter at extreme energy density. Quantum chromodynamics, the fundamental theory of nuclear forces, predicts that nuclear matter dissolves into quarks and gluons, the constituents of nucleons, when a critical energy density is exceeded. He and his collaborators are studying the properties of this quark-gluon plasma from the theoretical point of view. They are also developing the theory of the formation of a quark-gluon plasma and its possible detection in high-energy nuclear collisions. His lecture was given on February 4, 2011. | 6/14/11 | Free | View In iTunes |
| 18 | VideoThe Dark Energy Puzzle and The Cosmological Constant Problem | (Note: background noise the last 15 minutes) Abstract: We give an overview of the dark energy (DE) puzzle triggered by the 1998 dramatic discovery of the accelerating expansion of the universe and its possible solutions. Among the proposed solutions, the cosmological constant (CC) appears to be mathematically the simplest and observationally the most likely answer. If so, however, then we will be facing a challenging conceptual problem. There exists the long-standing CC problem that has bothered numerous physicists during most of the 20th century. Namely, why isn't CC zero? We shall call this the 'old' CC problem. Now the identification of CC as DE would induce a 'new' CC problem: Why is CC nonzero but so small? We will first review the various solutions to the CC Problem, old and new. Then we focus on a new proposal that attempts to solve both the 'old' and the 'new' CC problem based on the fusion of two concepts. The first is the suggestion that the proper description of classical gravitational effects is the gauge theory of gravity in which the connection instead of the metric acts as the dynamical variable. The second is the assumption that the universe obeys de Sitter symmetry, with the observed accelerating expansion as its manifestation. We discuss the implications of this theory and the challenges that it encounters. Dr. Pisin Chen's current research interests are theoretical cosmology, including the nature of dark matter and dark energy, inflation and cosmic evolution in early universe, theoretical particle astrophysics, such as ultra high energy cosmic rays (UHECR) and cosmic neutrinos, laboratory investigation of critical issues in high energy astrophysics and cosmology using high intensity particle and photon beams and experimental detection of ultra high energy cosmic neutrinos. His lecture was given on January 28, 2011. | 6/14/11 | Free | View In iTunes |
| 19 | VideoFemtosecond Frequency Combs: Precision Spectroscopy from the UV to EUV | NOTE: we are sorry that there is distracting background noise in the audio in different parts of Dr. Jones' lecture. Abstract: The fs frequency comb has proven to be a powerful tool in both precision spectroscopy and ultrafast science. By providing a direct phase-coherent link between optical and microwave frequencies it has dramatically simplified the precision measurement of optical transitions while simultaneously enabling access to sub-cycle control and synchronization f optical fields. It’s use has thus far been limited to wavelengths in the deep-UV or longer (>200 nm). In this talk, I will discuss 2 experiments utilizing the fs frequency comb for precision spectroscopy at UV and vacuum-ultraviolet (VUV) wavelengths. The first experimental effort is in the development of an optical atomic clock based on a narrow transition in neutral mercury atoms. A laser-cooled ensemble of mercury offers excellent prospects as a next generation optical frequency standard. The second effort is focused on extending precision spectroscopy into the VUV using intra-cavity high harmonic generation (HHG) with the fs frequency comb. I will discuss current results, simulations that highlight the limitations of this approach, and planned experiments utilizing this source. Dr. R. Jason Jones is Assistant Professor of Optical Sciences at the University of Arizona. His current research interests are in ultrafast laser science, femtosecond frequency combs, extreme nonlinear light/matter interactions and generation, optical frequency metrology, and high-resolution spectroscopy. His lecture was given on January 21, 2011. | 6/14/11 | Free | View In iTunes |
| 20 | VideoAtomic Dipole Polarizability | Abstract: The advent of cold-atom physics owes its existence to the ability to manipulate groups of atoms with electromagnetic fields. Consequently, many topics in the area of field-atom interactions have recently been the subject of considerable interest and heightened importance. This applies to a quantity like the dipole polarizability which governs the first-order response of an atom to an applied electric field. Atomic polarization phenomena impinge upon a number of areas and processes in physics. An imperfect knowledge of atomic polarizabilities is presently looming as the largest source of uncertainty in the new generation of optical frequency standards. More precise atomic clocks will open ways to more sensitive quantum-based standards for many applications such as searches for variation of the fundamental constants, testing of physics postulates, gravity gradiometry, inertial navigation, and tracking of deep-space probes. In this talk, I will review existing theoretical methods of determining atomic and ionic polarizabilities, and discusses their relevance to various applications with particular emphasis on development of optical frequency standards, quantum computing, and study of parity violation. Dr. Marianna Safronova is Associate Professor in the University of Delaware Physics Department. Her research involves both the study of the fundamental physics problems (fundamental symmetries) and applications of atomic physics to future technological developments (such as quantum computing and optical atomic clocks). Among her current research projects include: modeling of trapped atoms for atomic clocks and quantum information, parity violation of atoms, development of new relativistic high-precision methodologies for atomic calculations, and calculation of atomic properties for various applications. Her lecture was given on September 10, 2010. | 6/14/11 | Free | View In iTunes |
| 21 | VideoSpin-orbit Nanodevices | Some of the most promising new approaches to information processing rely on spin. Spintronics may offer higher energy efficiency, greater storage capacity and speed. Electron spin is a natural quantum two-level system with long coherence times. This makes spin the leading candidate for solid state quantum computing. A big challenge is to find a practical way of controlling spin on the nanoscale. Normally spin couples only to magnetic fields. But magnetic fields are hard to generate on a chip, especially at high frequencies required for both classical and quantum computing. A much preferred control knob is the one that was the key to success for charge-based electronics a gate voltage or an electric field. It turns out that in semiconductors it is possible to couple spin to electric fields. Through spin-orbit interaction we can control spin by simply moving the electron around. I will describe several of our experiments that were enabled by spin-orbit interaction. In two-dimensional electron gases, we have observed a new type of spin resonance ballistic spin resonance and used it to build a spin field-effect transistor. In nanowires, we have realized a spin-orbit qubit. We confined single electrons to quantum dots and performed coherent spin manipulation using electric fields. These experiments offer unique insights into the physics of spin in semiconductors. Dr. Frolov is an experimentalist at the Kavli Institute of Nanoscience, Delft University of Technology. Presented November 15, 2010. | 12/19/10 | Free | View In iTunes |
| 22 | VideoExploring One Layer of Carbon Atoms - Graphene | Abstract: Graphene, a single atomic layer of graphite, is a unique material characterized by Dirac quasiparticles with linear energy-momentum dispersion. This exotic property gives rise to numerous intriguing phenomena such as room temperature quantum Hall effects and perfect tunneling through any energy barriers. The electronic band structure of this material can be readily tailored by many methods, thus providing a wide range of opportunities for device applications. In this talk, I will present our recent investigations on graphene employing synchrotron based infrared spectroscopy. Our measurements directly demonstrated the Dirac nature of the charge carriers in graphene and revealed several signatures of many body interactions. We further found that the coupling of graphene sheets leads to entirely new properties in few-layer graphene. These studies have broad implications in the fundamental understanding of graphene as well as its future applications. Presented November 17, 2010. Dr. Zhiqiang Li research Interests: Investigate electronic and magnetic properties of novel materials employing spectroscopic techniques such as infrared and magneto-optical spectroscopy, microscopy, and ellipsometry. | 12/19/10 | Free | View In iTunes |
| 23 | VideoNeutrinos, Nature's Messengers | Abstract: Over the past decade, physicists and astrophysicists have examined signals from neutrino interactions to learn about fundamental properties of matter. In this talk, I will review the discovery of the quantum mechanical phenomenon of neutrino oscillations. Looking forward, the potential for neutrino signals to yield new information is great. I will discuss how neutrinos will help us explore the standard model of particle physics in new energy regimes and how neutrinos may help us understand the cosmos. For example, the properties of the highest energy astrophysical accelerators may be uncovered with neutrino signals. Neutrinos may also reveal the nature of the dark matter in the universe. Dr. Hallsie Reno is Professor and Chair, Department of Physics & Astronomy, The University of Iowa. Her research area is Theoretical High Energy Physics. Presented December 3, 2010. | 12/19/10 | Free | View In iTunes |
| 24 | VideoThe IBEX Ribbon: Unexpected Observations of the Interaction of the Heliosphere with the Intersteller Medium | Abstract: The Sun and its radially flowing solar wind blow a huge bubble, a few hundred AU in scale, in the interstellar medium. This results in a very complicated interaction between the resulting heliosphere and the local interstellar medium. The solar wind is a very nearly completely ionized plasma, whereas the local interstellar medium is only partly ionized, and therefore consists of both charged and neutral particles. The collision mean free paths of all species are much larger than the scale of the heliosphere, so the interactions do not involve particle-particle scattering. The ions interact via collective electromagnetic interactions and the neutrals can be ionized by solar radiation and through charge exchange with ions. his region was predicted decades ago and, recently, the two Voyager spacecraft are traversing in this region, sending back data. The IBEX (Interstellar Boundary EXplorer) mission, launched on October 19, 2008, was developed to observe this region remotely, from Earth orbit, by measuring energetic neutral atoms (ENA) resulting from the interaction with the neutral part of the Interstellar Medium. Because of the lack of collisions and the relatively high energy of the ENA, they travel on nearly straight lines, and can be used much like photons to map the sky. IBEX began sending data to ground six months after launch, and is still doing so. In spite of intensivetheoretical an modeling efforts over the past decades, much of what is observed was totally unexpected and not even hinted at in the models. The observed ENA maps, at the higher energies observed, revealed an intense "ribbon" of significantly enhanced intensity, some 15 degrees wide, encircling the solar system. This unexpected feature and other aspects of the observations have required new models and interpretations. Dr. J. Randy Jokipii is Regents' Professor, Theoretical astrophysics, space physics at the University of Arizona. Presented Oct. 29, 2010. | 12/19/10 | Free | View In iTunes |
| 25 | VideoQwark Matter Under Extreme Conditions | Abstract: A major ongoing research effort in nuclear and particle physics is focused in improving our understanding of the properties of matter under extreme conditions. A main goal is mapping the QCD phases at different regions of temperature and densities. At present, we know of (at least) three fundamental states of matter in QCD that exist in the extreme regions of temperature and/or density. They are the hadronic matter with broken chiral symmetry and quark confinement, the quark-gluon plasma, and the color superconductivity. Exploration of a wider range of the QCD phase diagram with densities up to several times the normal nuclear matter density is expected to be carried out in the near future at RHIC and at planned facilities all over the world (FAIR, NICA, J-PARC). The QCD phase diagram becomes even richer in the presence of a magnetic field. In this colloquium I will review our current understanding of the physical properties of quark matter at ultra-high density in the presence of very large magnetic fields and will mention some recent results in the region of intermediate densities. Dr. Incera is Chair of the Physics Department, University of Texas, El Paso, Physics Department. Presented October 15, 2010. | 12/19/10 | Free | View In iTunes |
| 26 | VideoUltrafast Manipulation of Single Electronic and Nuclear Spins in Diamond | Abstract: Nitrogen vacancy (NV) center spins in diamond have emerged as a promising solid-state system for quantum information and precision metrology at room temperature. Fast, coherent control and storage of quantum information is crucial due to the practical need for fault tolerance. Manipulation of a two-level system (a spin) is typically performed under the rotating wave approximation (RWA) which assumes that an oscillating field can be approximated by a rotating field. We present high-speed microwave experiments probing the spin dynamics of single NV centers in diamond driven by a large amplitude oscillating field where this approximation is not valid. Using lithographically patterned coplanar waveguides on the diamond substrate, we drive spin rotation on the same timescale as Larmor precession. Coherent spin flips still occur under these conditions, but with sub-nanosecond timescales, faster than expected from the RWA. In addition to ground-state spin manipulation, we apply these techniques to study the spin coherence of single NV centers in their orbital excited state (ES). We demonstrate ES Rabi oscillations and use multi-pulse resonant control to differentiate between phonon-induced dephasing, orbital relaxation, and coherent electron-nuclear interactions. Finally, extending our coplanar waveguide approach, we fabricate a high-bandwidth two-axis vector magnet on diamond to perform a coherent swap operation between a single NV centerelectronic spin and the associated nitrogen nuclear spin to demonstrate a nuclear spin quantum memory. These experiments provide tools for coherently manipulating and storing quantum information in a scalable solid-state system at room temperature. Gregory D. Fuchs was with the Center for Spintronics and Quantum Computation University of California, Santa Barbara. Presented October 6, 2010. | 12/18/10 | Free | View In iTunes |
| 27 | VideoIsotopes for Science and Medicine | Physicians and the public are increasingly being made aware and at the same time becoming anxious about the availability of medical isotopes. These seemingly exotic compounds are at the heart of medical scans that touch the lives of about 20 million people world-wide every year. Yet, the supply relies on aging nuclear reactors, the result of which has led to severe shortages around the world on and off for the past three years. The shortages are both a problem and an opportunity. Innovative production methods are now being explored and may herald a revolution. Canada produces about 40% of the worlds isotopes primarily with a 50-year old reactor. The Government of Canada has made a bold decision to abandon its chief nuclear-research reactor and has asked its scientific and technical community to come up with a new way of making medical isotopes. Although at first it sounds risky, the pay off may be quite large. Members of the basic science community in Canada, which includes physicists, chemists, biologists and medical doctors have aligned with numerous businesses to meet the challenge. Yes, basic scientific research is essential to innovation. A case study will be presented. In addition, the growth of medical imaging and therapies has led to other innovations that will be explored. Prof. Nigel Lockyer is a Professor of Physics at the University of Pennsylvania and Director of TRIUMF. He was educated at York University in Toronto, Canada. Presented October 1, 2010. | 12/18/10 | Free | View In iTunes |
| 28 | VideoThere's Plenty of Room at the Bottom … and Time at the Top! | Abstract: Over fifty years ago, Feynman predicted the rise of nanotechnology, even before it was on the horizon. Today, not only have we made significant strides in the fields he proposed nanomedicine, nanolithography and nanofabrication; but we have developed tools that allow us to go "small" in the "other" component of space time. With the advent of femtosecond pulses of light, we have been able to pursue physics at the femtosecond timescale in systems characterized by a nanometer length scale. In todays talk, I will present three very different ideas from my own research background that involve physics at the femto-nano scale. Using a Metamaterial – an artificially fabricated nano-material, I will demonstrate the ability to do develop ultrafast, nanoscale, tunable, photonic devices. Next, in graphene, a newly discovered allotrope of carbon, using a counter intuitive technique in ultrafast spectroscopy, I will demonstrate the relativistic nature of Dirac Quasiparticles. Lastly, in the quantum Hall system, a two-dimensional electron gas in a large magnetic field, I will demonstrate the photoexcitation of complex, many-body states and then observe their quantum interference that can been seen only within the first few hundred femtoseconds. Dr. Dani is with the Los Alamos National Laboratory. Presented Sept. 17, 2010. | 12/18/10 | Free | View In iTunes |
| 29 | VideoSuperconductivity in Strongly Correlated Electron Systems: Beyond the Quantum Spin Liquid Approach | Prior to the advent of the Bardeen-Cooper-Schrieffer (BCS) theory in 1957, superconductivity had been referred to as the shame of quantum mechanics. It took forty-six years after the first observation of this phenomenon to arrive at a coherent explanation. Over the past two decades (three according to some) we have seen a recurrence of this, when superconductivity was discovered in a number of materials in which there occur strong repulsive electron-electron interactions, and which therefore lie outside the scope of the BCS theory. One approach to this new class of materials has been to focus on their magnetic behavior. The concept of a quantum spin liquid (QSL) has acquired popularity, but not necessarily success. In this talk I will discuss the need to go beyond QSL theories, and develop the concept of a paired-electron crystal, which is a semiconductor with paired electrons. I will then posit that a superconductor is a paired-electron liquid and present justifications based on experiments. The talk was given on Aug. 27, 2010, and is directed towards nonexpert graduate students. Experts will find overlaps with the RVB theory, the bipolaron theory and stripe concepts. | 12/18/10 | Free | View In iTunes |
| 30 | VideoQuasi-One-Dimensional Electron Systems | Abstract: In the presence of interactions, one-dimensional (1D) systems behave very differently from their higher-dimensional counterparts. Fermi liquid theory breaks down: the elementary excitations in 1D are not electron-like. Instead the 1D system is a so-called Tomonaga-Luttinger liquid with collective excitations. In experiment, signatures of one-dimensional (1D) behavior have, e.g., been observed in quantum wires and carbon nanotubes as well as cold atomic gases. While the 1D aspects make the above mentioned systems so fascinating, the real world is three-dimensional and, therefore, even in these confined geometries, features pertaining to deviations from one-dimensionality may remain. My interest is in identifying how the one-dimensional effects are modified in realistic situations and exploring the novel phenomena that arise. The colloquium will address the transition from a one-dimensional to a quasi-one-dimensional state of interacting electrons in a quantum wire as well as interesting spin properties in the quasi-one-dimensional regime. Julia S. Meyer, from The Ohio State University, visited the University of Arizona as a UA ADVANCE Junior Scientist Speaker and gave a 50- to 60-minute lecture on her research as part of the physics department lecture series. Philippe R. Jacquod, associate professor of physics, nominated her for the award. With the need to miniaturize electronic components below the nanoscale barrier, low-dimensional physics has come to play a central role in modern condensed matter physics and nanoscience. Meyer's research investigates the interplay between low dimensionality as well as interactions and disorder in nanoelectronic systems. These aspects are key to understanding how electricity is transmitted across such systems, a necessary step if one wants to include them as building blocks in nanoscale electronic circuits. Some of Meyer's more spectacular theoretical results include the construction of the phase diagram for interacting electrons in quantum wires, with the emergence of paramagnetic and (finite-sized) ferromagnetic phases, and the breakdown of Luttinger physics with the emergence of a single, fermionic gapless mode. September 11, 2009. | 6/15/10 | Free | View In iTunes |
| 31 | VideoIndividual and Collective Dynamics of Micro-Swimmers | Abstract: The swimming of micro-organisms is governed by "Low Reynolds number" fluid dynamics where shear force Fy ~ dVy/dx replaces the "usual" Fx ~dVx/dt. A brief introduction to that "world" will follow a briefer recounting of pertinent history. Spatial ordering and collective coherent dynamics of algal and bacterial cell populations emerges from local interactions and from the flow and molecular concentration fields that surround individuals. Experimental results shown and discussed will feature collective gravitational interactions of algae (green holes), accumulations of algae in thin oceanic layers (blooms and red tides), bound pairs of swimming bacteria, and the ZBN (Zooming BioNematic) of concentrated (~10^11 cells/cm^3) bacteria. Is this stuff significant? Well, for starters, the entire world's biomass as well as the functioning of all macro-organisms (including you) is dominated by just such creatures! Dr. Kessler is Professor Emeritus of Physics. Presented October 16, 2009. | 6/15/10 | Free | View In iTunes |
| 32 | VideoThe Origins of the Universe and the Arrow of Time | Abstract: Over a century ago, Boltzmann and others provided a microscopic understanding for the tendency of entropy to increase. But this understanding relies ultimately on an empirical fact about cosmology: the early universe had a very low entropy. Why was it like that? Cosmologists aspire to provide a dynamical explanation for the observed state of the universe, but have had very little to say about the dramatic asymmetry between early times and late times. I will argue that the observed breakdown of time-reversal symmetry in statistical mechanics provides good evidence that we live in a multiverse. Dr. Carroll is a theoretical physicist at Caltech in Pasadena, California. Presented April 23, 2010. | 5/11/10 | Free | View In iTunes |
| 33 | VideoSearches for the Higgs Boson at the Tevatron | Abstract: Unraveling the secret of electroweak symmetry breaking remains one of the highest priorities in particle physics research, with the elusive Higgs boson being a center piece of many theoretical constructions. A comprehensive program of searches for the Higgs boson is underway at the Fermilab Tevatron Collider, which has started to sensitively probe previously unchartered territory. We will present the latest results on the Higgs boson search from the CDF and D0 experiments using up to 5.4/fb of integrated luminosity, including a recent combined result with improved sensitivity. We will also discuss the future prospects for Higgs boson searches at the Tevatron. Presented April 2, 2010. | 5/11/10 | Free | View In iTunes |
| 34 | VideoLasing and Cooling in Circuit QED | Abstract: Motivated by recent experiments, which demonstrated lasing and cooling of the electromagnetic modes in a resonator coupled to a superconducting qubit, we describe the specific mechanisms creating the population inversion, and we study the spectral properties of these systems in the lasing state. Different levels of the theoretical description, i.e., the semi-classical and the semi-quantum approximation, as well as an analysis based on the full Liouville equation are compared. We extend the usual quantum optics description to account for strong qubit-resonator coupling and include the effects of low-frequency noise. Beyond the lasing transition we find for a single- or few-qubit system the phase diffusion strength to grow with the coupling strength, which in turn deteriorates the lasing state. Dr. Schön is a physicist with Institut für Theoretische Festkörperphysik, Karlsruher Institut für Technologie (Universität). Presented April 7, 2010. | 5/11/10 | Free | View In iTunes |
| 35 | VideoBeyond the WIMP Miracle | Abstract: Weak Interacting Massive Particle (WIMP) has been a popular dark matter candidate, which naturally appears in many beyond the Standard Model new physics scenarios. In this talk, I will present several recent theoretical developments in dark matter candidates that are closely related to the WIMP miracle: superWIMP scenario and Wimpless scenario. I will also discuss how to study those dark matter scenarios at both high energy colliders and dark matter detection experiments. Presented March 26, 2010. | 5/11/10 | Free | View In iTunes |
| 36 | VideoMedical Physics at the University of Arizona | Abstract: Medical physics is the bridge that brings the res oalmf physics and medicine together. The study and practice of medical physics covers four primary sub-fields: radiation therapy, diagnostic imaging, nuclear medicine and medical health physics. Each of these categories will be discussed. Additional discussion on current topics in medical physics education, professional issues and research will be presented. A short review of the UA PSM-Medical Physics program will also be presented. Current on-going research project in radiation oncology physics at UA will be discussed. Some of these projects include computational simulation for radiation dosimetry, equipment/protocol evaluation and development of a dynamic phantom. Dr. Watchman earned his undergraduate degree in physics and exercise physiology at Brigham Young University. He received a graduate degree in health physics at Iowa State University, and a doctorate in medical physics at Florida State University. Prior to his appointment as assistant professor at the Arizona Cancer Center, Dr. Watchman completed residency training in radiation oncology physics at the University of Arizona in 2007. He is a board-eligible medical physicist. Presented March 5, 2010. | 3/15/10 | Free | View In iTunes |
| 37 | VideoEntropy and Time | Abstract: The emergence of a direction of time in statistical mechanics from an underlying motion-reversal-invariant dynamics will be discussed in a tutorial way. The urn (dog-flea) model of P. and T. Ehrenfest, generalized to finite temperature, will be used to illustrate the main points, with emphasis on the role of initial conditions and the manner in which time-reversal symmetry is preserved. The transformation of the principle of no decrease of entropy for an isolated system to the principle of no increase of free energy for a system at fixed temperature will be demonstrated in a simple way. 'Master Equation' and 'Monte Carlo' methods will be used, including reliable estimates of errors. Dr. Vinay Ambegaokar is Goldwin Smith Professor of Physics Emeritus Presented February 5, 2010. | 3/11/10 | Free | View In iTunes |
| 38 | VideoAtoms in Motion: The Remarkable Connections Between Atomic and Hadronic Physics | Abstract: Quantum Electrodynamics (QED), the fundamental theory underlying atomic physics, shares the same Lagrangian as Quantum Chromodynamics (QCD), the theory underlying hadronic and nuclear physics. Insights from both theories enrich each other. For example, the light-front methods which underly phenomenology in high energy physics also have remarkable advantages for describing the wavefunctions of atoms in motion. The conversion of muonic atoms to electronic atoms provides a direct analog for the weak decay of hadrons such as the B meson. "True muonium", theatomic bound state of a muon and antimuon, is the QED analog of heavy quarkonium in QCD. Electron-positron pair production at high field strength in QED has features in common with the confinement dynamics of QCD. I will also discuss how the production of relativistic antihydrogen has provided important insight into the hadronization of quarks and gluons of QCD at the amplitude level. Dr. Brodsky is a Professor at SLAC (Stanford Synchrotron Radiation Lightsource) in the Theoretical Physics Group.Presented Feb. 26, 2010. | 3/11/10 | Free | View In iTunes |
| 39 | VideoNanoengineered Photonics for Novel Sensing and Imaging Applications | Abstract: Until recently optical applications of metals have been limited to reflectors, due to their large free electron densities, even in the optics laboratories. Surface plasmons in nanoengineered metal structures have provided a basis for new applications extending from chemical and biological sensing to heat-assisted magnetic recording for next generation hard drives. I will first introduce a new active nanophotonic device, namely, the plasmonic laser antenna that was announced as one of the 10 emerging technologies of 2007 by the MIT Technology Review. Our plasmonic device comprises a semiconductor laser diode with optical nanoantennas integrated directly onto its facet. This new class of devices can break the diffraction limit on demand by confining and enhancing light on the nanometer scale. I will also describe a surface enhanced molecular detection technique with zeptomole sensitivity per element that relies on resonant coupling of plasmonic modes of split ring resonator antennas and infrared vibrational modes of a self-assembled molecular monolayer chemisorbed in the antenna gap. Finally, I will discuss a new nanoimaging modality that utilizes aligned single-wall carbon nanotubes as polarization-sensitive molecular scale Raman near-field detectors. Presented Feb. 24, 2010. | 3/11/10 | Free | View In iTunes |
| 40 | VideoUltrafast Physics in Photosynthesis: Mapping Sub-Naometer Enery Flow | Abstract: In the first picoseconds of photosynthesis, photoexcitations of chlorophyll molecules are passed through a network of chlorophyll-binding proteins to a charge transfer site, initiating the conversion of absorbed energy to chemical fuels. The remarkably high quantum efficiency of this energy transfer relies on near-field coupling between adjacent chlorophyll molecules and their interaction with protein phonon modes. Using two-dimensional electronic spectroscopy, we track the time-evolution of energy flow in a chlorophyll-protein complex, CP29, found in green plants. The results from these nonlinear four-wave mixing experiments elucidate the role of CP29 as a light harvester and energy conduit by drawing causal relationships between the spatial and electronic configurations of its chlorophyll molecules. Through independent control of experimental light pulse polarizations, we have furthermore developed a technique to determine the relative angles between the transition dip ole moments responsible for energy transfer. This work not only yields tools for structural and spectral molecular characterization, but also deepens our understanding of how photosynthetic systems have evolved to optimize the conversion of light to biomass. Naomi Ginsberg is Assistant Professor of Chemistry Cupola Era Endowed Chair in the College of Chemistry at UC-Berkeley. Presented Feb. 17, 2010. | 3/11/10 | Free | View In iTunes |
| 41 | VideoRecent Progress in Plasmonic Optical Metamaterials | Abstract: Refractive index is one of the most fundamental parameters to describe the interaction of electromagnetic radiation with matter. It is a complex number where real part has generally been considered to be positive. While negative refractive index does not violate any physical law, materials with negative index have some unusual and counterintuitive properties. For example, light refracted at an interface between positive and negative index materials is bent in the "wrong" way with respect to the normal. In this case, the wave and Pointing vectors are anti-parallel, and three vectors, electric and magnetic fields, and wave vector form a left-handed system. In this talk I will discuss our experimental realizations of negative index materials (NIMs) at telecommunication wavelength and in the visible range. Our designs make use of localized surface plasmons in metal nanostructures. The samples of a subwavelength bi-periodic cross-grating, consisting of two perforated thin metal layers separated by a thin dielectric show both a negative effective permeability and a negative effective permittivity, and consequently negative real part of its refractive index. Metamaterials with negative effective permeability across the whole visible range have been realized with sub-wavelength gratings of paired strips. We have demonstrated a thermally tunable optical metamaterial with negative permeability working in the visible range by covering coupled metallic nanostrips with aligned nematic liquid crystals. We will discuss also the basic properties of metal nanostructures, including effect of grain boundaries and surface roughness on the metal permittivity responsible for losses and effective parameters of metamaterials. Generally, the losses are orders of magnitude too large for the envisioned applications, and the reduction of losses with optimized designs appears to be out of reach. Our recent work experimentally demonstrates that the incorporation of gain material in the high-local field areas of a NIM enables a lossless optical metamaterial. Vladimir P Drachev is Senior Research Scientist at Purdue's Birck Nanotechnology Center. School of Electrical and Computer Engineering. Presented Feb. 12, 2010. | 3/11/10 | Free | View In iTunes |
| 42 | VideoFilamentation of Beam-Shaped Ultraintense Laser Pulses in Transparent Dielectics | Abstract: When ultra-intense and ultra-short optical pulses propagate in transparent dielectrics, the dynamic balance between multiple linear and nonlinear effects results in the generation of so-called laser filaments. These peculiar objects have numerous interesting properties and can be potentially used in a variety of applications from remote sensing to optical pulse compression down to few optical cycles to guiding lightning discharges away from sensitive sites. Materializing this practical potential is not straightforward owing to the complexity of the physical picture of filamentation. I will discuss recent experiments on using beam shaping as a means of control over filament formation and dynamics. Two particular beam shapes we have investigated so far are Bessel and Airy beams. The diffraction-free propagation of femtosecond Bessel beams allows for the creation of extended plasma channels in air. These extended filaments can be used for the generation of energetic optical pulses with duration in the few-cycle range. In the case of filamentation of femtosecond Airy beams, the self-bending property of these beams allows for the creation of curved filaments. This is a new regime of the intense laser-pulse propagation in which the linear self-bending property of the beam competes against the nonlinear self-channeling. The bent filaments generated by ultra-intense Airy beams emit a forward-propagating broadband radiation. Analysis of the spatial and spectral distribution of this emission provides a valuable tool for analyzing the evolution of the ultra-intense optical pulse along the optical path. Dr. Polynkin is Associate Research Professor, Optical Sciences, The University of Arizona. Presented Feb. 3, 2010. | 3/11/10 | Free | View In iTunes |
| 43 | VideoSolar Power in Arizona | Abstract: Using photovoltaic (PV) systems to provide a significant portion of the world's electrical power is on the verge of being a great idea. But there are still major challenges regarding the cost, reliability, and efficiency of solar cells, and the storage and transmission of electrical energy. In this talk I will describe field tests of PV systems in Arizona and I will report on several factors that affect the output of existing PV systems. Using these observations I will then discuss ways to make solar power cheaper and more reliable. Dr. Cronin is Assistant Professor of Physics. The University of Arizona Dept. of Physics. Presented Nov. 20, 2009. | 3/11/10 | Free | View In iTunes |
| 44 | VideoIs the World Fine-Tuned? | Abstract: Much model building in particle physics and some discussion in theology revolve around the possibility that certain physical parameters are fine-tuned. Much model b to yield the world we live in. A famous example is the smallness of the resonance energy in the triple-alpha nuclear reaction, which is crucial for the observed abundances of carbon and oxigen, and thus life. Fine-tuning is best formulated in the framework of effective field theories (EFTs), which I will introduce together with the concept of naturalness. Using EFT, I will present our current understanding of the emergence of an anomalously small nuclear scale,nshow examples of the rich physgcs it generates, and discuss plans for further study of nuclear fine-tuning. Dr. van Kolck is Professor at the Department of Physics University of Arizona and also Affiliate Professor at the Department of Physics University of Washington. His main research is on Effective Field Theories (EFTs), in particular their applications to problems at the interface between particle and nuclear physics, and to problems in molecular physics. Presented Dec. 4, 2009. | 3/11/10 | Free | View In iTunes |
| 45 | VideoGalactic Positron Annihilation: Mysteries Solved | Abstract: The ratio of the luminosity of diffuse 511 keV positron annihilation radiation, measured by INTEGRAL/SPI in its four years, from a Galactic "positron bulge" compared to that of the disk is 1.4. This ratio is roughly 4 times larger than that of positron production expected simply from the stellar bulge-to-disk ratio of ~0.33 of the Galactic supernovae, which are thought to be the principal source of the annihilating positrons through the decay of radionuclei made by explosive nucleosynthesis in the supernovae. This large disDcrepancy, oft quoted as a "Big Mystery", has prompted searches for new sources, including a large number of dark matter scenarios. We show, however, that the measured 511 keV luminosity can be fully understood in the context of a Galactic supernova origin, when the propagation of the relativistic positrons in the various phases of the interstellar medium is taken into consideration, since the positrons must slow to eV energies before they can annihilate. This explanation accounts for the observed positronium fraction and line widths. The observed asymmetry in the inner disk annihilation flux is also fully understood from positron propagation and the asymmetry in the inner spiral arms as viewed from our solar perspective without additional sources. An assumption of very little propagation of positrons and the observed difference between the annihilation flux distribution and that of positron production has been evoked as evidence of a new source and signal of dark matter. Such models cannot account for the positronium fraction and yet with propagation standard nucleosynthetic sources can fully account for all measured quantities of the annihilation radiation, leaving no signal for dark matter to explain. Dr. Richard E. Rothschild is Research Physicist and Principal Investigator, HEXTE, Center for Astrophysics & Space Sciences, University of California, San Diego. Presented Nov. 13, 2009. | 2/23/10 | Free | View In iTunes |
| 46 | VideoNeutrino Oscillations: Recent Triumphs and Future Challenges | Abstract: Recent studies of neutrino oscillations have established the existence of finite neutrino masses and mixing between generations of neutrinos. The combined results from studies of atmospheric neutrinos, solar neutrinos, reactor antineutrinos and neutrinos produced at accelerators paint an intriguing picture that clearly requires modification of the standard model of particle physics. These results also provide clear motivation for future neutrino oscillation experiments as well as searches for direct neutrino mass and nuclear double-beta decay. I will summarize the status of experimental and theoretical work in this field and discuss the future opportunities that have emerged in light of recent discoveries. Dr. McKeown has been the deputy director for science at Jefferson Lab since May 2010. He also serves as a Governor's Distinguished CEBAF Professor at The College of William and Mary. Presented Oct. 23, 2009. | 2/23/10 | Free | View In iTunes |
| 47 | VideoRecent Advances and Challenges in Nuclear Structure Physics | Abstract: Low energy nuclear structure physics is entering an exciting new era. Experimentally a new generation of rare isotope accelerators, such as the Rare Isotope Beam Facility (RIBF) in Japan, the Facility for Antiproton and Ion Research (FAIR) in Germany, the Systeme de Production d'Ions Radioactifs en Ligne, RIB Facility (SPIRAL) in France, and the Facility for Rare Isotope Beams (FRIB), to be constructed at Michigan State University, will allow for the study of so-called exotic nuclei, i.e., those nuclei far from the line of stability and near the proton and neutron drip lines. Theoretically great progress has been made in the last ten years in understanding the structure and properties of the atomic nucleus starting from the basic interactions among the neutrons and the protons (collectively called nucleons) and employing only quantum mechanical many-body theory. This progress is due to new developments in nuclear many-body theory and advances in computer technology (see, e.g., Physics Today, 60, No. 11, 48 (2007)). Research at the University of Arizona has been at the forefront of these investigations with the development of the No Core Shell Model (NCSM), which can successfully describe the properties of light nuclei starting from the fundamental interactions among the nucleons. The NCSM will be described, examples of applications will be given and challenges for the future will be discussed. Dr. Barrett's research interest centers on nuclear-structure theory, mainly on microscopic theories of nuclear structure utilizing the large-basis, no-core shell-model approach and the quantum many-body theory of effective interactions and operators.Presented Sept. 18, 2009. | 2/22/10 | Free | View In iTunes |
| 48 | VideoCluster Cosmology and the Dark Energy Survey | Abstract: The discovery of accelerated cosmic expansion showed us that cosmology remains incomplete. A new element is required. This may be a cosmological constant, a more exotic form of dark energy, or a failure of general relativity on large scales. Galaxy clusters provide a powerful tool for discriminating among these possibilities. I will describe the strengths and weaknesses of clusters as cosmological probes, illustrate these with recent analyses of SDSS clusters, and discuss the prospects for future constraints, especially in the Dark Energy Survey project. Dr. McKay is Arthur F. Thurnau Professor of Physics. His scientific research focuses on fundamental questions of observational astrophysics and cosmology. . Presented October 9, 2009. | 2/22/10 | Free | View In iTunes |
| 49 | VideoAtomic-scale Magnetism Probed with Spin Excitation Spectroscopy | Dr. Andreas Heinrich leads the scanning probe microscopy project at IBM Research's Almaden lab in San Jose, CA. The experiments conducted by Heinrich's group aim to extend the basic knowledge about the physics, chemistry, and materials properties of atomic-scale structures with a focus on exploring potential applications of nanostructures for atomic-scale logic and data-storage. Heinrich joined the IBM research group of Dr. Donald Eigler as a postdoctoral researcher in 1998 where he built a next-generation low-temperature scanning tunneling microscope operating at temperatures below 1K and in high magnetic fields. In January 2005, Heinrich took over the leadership of the STM lab. He is devoted to educating the general public about the excitement of nanotechnology through hands-on demonstrations, is the author or co-author of papers published in the highest-ranking international journals and has given over 50 invited talks at international conferences. Heinrich received his Ph.D. in 1998 from the University of Goettingen in Germany where he studied the materials properties of ternary compound semiconductors. Presented March 6, 2009. | 9/9/09 | Free | View In iTunes |
| 50 | VideoHow to Weigh a Quark: an introduction to lattice QCD | Dr. Toussaint's research involves the use of massively parallel computers to calculate some of the most fundamental quantities in high energy physics. He employs lattice gauge theory to calculate the masses and lifetimes of strongly interacting particles, the weak interactions of these particles, the behavior of nuclear matter at very high temperatures, and the structure of the electroweak interactions. Presented 2008. | 9/3/09 | Free | View In iTunes |
| 51 | VideoConsequences of Turbulence for a Supernova Blast Wave | Dr. Jokipii is Regents' Professor Randy Jokpii, UA Departments of Planetary Sciences and Astronomy. Presented March 13, 2009. | 9/3/09 | Free | View In iTunes |
| 52 | VideoPuzzle: Mass and Gravity | Professor Landsberg does research in elementary particle physics, specifically experimental investigation of the fundamental particles and fields at the energy frontier accelerators. His main research activity is the search for new physics phenomena, including extra dimensions in space. He is a member of the CMS and DZero experiments operating at the energy-frontier facilities: the Fermilab Tevatron collider (Batavia, IL) and the Large Hadron Collider at CERN (Geneva, Switzerland). Presented April 24, 2009 | 8/17/09 | Free | View In iTunes |
| 53 | VideoNanodevices and Maxwell's Demon | Dr. Datta is Thomas Duncan Distinguished Professor of Electrical and Computer Engineering at Purdue University. His research interests are: Physics of Nanostructures with emphasis on Electronic Transport including Spin Electronics, Molecular Conduction, Nanoscale Device Physics and Mesoscopic Superconductivity. Presented April 17, 2009. | 8/17/09 | Free | View In iTunes |
| 54 | VideoComprehensive High Frequency Electron Paramagnetic Resonance Studies of Single Molecule Magnets | Jon Lawrence emphasis is that HFEPR can be used in a variety of ways in order to characterized these magnetic compounds: spin Hamiltonian parameters, effects of disorder, & isolate different molecules within a distribution. He found the potential to combine this with other techniques to measure multiple processes simultaneously. Presented on Jan. 23, 2009. | 8/11/09 | Free | View In iTunes |
| 55 | VideoMeasurement of the W Boson Helicity in Top Quark Decays | Abstract: The precision and variety of top quark measurements is rapidly improving. It is: highlighted by mass measurement with precision of 0.8%; several measurement of interaction and decay properties; as well as searches for new particles, have not yet revealed any non-SM effects. The era of single-top production measurements has begun. The LHC will provide a major improvement in precision. We have learned much about the top quark in the past 13 years. In a few more years it will be as familiar as the Z boson and b quark. Dr. Varnes is currently working with the D0 experiment at Fermilab National Laboratory. This experiment records collisions bewteen 1 TeV proton and antiproton beams, allowing us to search for new particles more massive than those seen previously. Presented 2009. | 7/26/09 | Free | View In iTunes |
| 56 | VideoCosmology as Science? From Inflation to Eternity | Abstract: Are fundamental cosmological questions falsifiable? During this presentation we discussed "proving inflation, Physics as an environmental science, dark ignorance and falsifably false cosmology. Presented Feb. 2009. Lawrence M. Krauss is an internationally known theoretical physicist whose research covers science from the beginning of the universe to the end of the universe. His research interests include the interface between elementary particle physics and cosmology, the nature of dark matter, general relativity and neutrino astrophysics. He has investigated questions ranging from the nature of exploding stars to issues of the origin of all mass in the universe. Krauss is the author of many scientific publications, as well as several acclaimed popular books, including, "The Fifth Essence", "Fear of Physics", and "The Physics of Star Trek." | 6/10/09 | Free | View In iTunes |
| 57 | VideoUltrafast Quantum Control | Dr. Bucksbaum is an atomic physicist. His main research interest is fundamental light-matter interactions, and especially the control of quantum systems using ultrafast laser fields. He develops new sources of ultrafast laser light in the infrared, visible, ultraviolet, and x-ray regions of the light spectrum. He is Professor of Physics and Professor of Applied Physics and Director of the Ultrafast Science Center, SLAC, Stanford University. His presentation was on Feb. 27, 2009. | 6/10/09 | Free | View In iTunes |
| 58 | VideoAngels & Demons Science Revealed: The Science of Antimatter & The Large Hadron Collider | Erich Varnes Associate Professor of Physics at The University of Arizona, spoke about the physics behind the movie "Angels & Demons." Varnes is part of the team of UA physicists working on the ATLAS detector, one of the experiments that is part of the Large Hadron Collider. The LHC is the world's largest particle collider and the largest scientific instrument ever built. The experiments conducted using the LHC will provide fundamental discoveries about the matter that makes up our universe. The UA is the only university in Arizona involved with the LHC. The international effort involves 2,500 scientists from 37 countries. The LHC is operated by CERN. Presented May 13, 2009. | 5/26/09 | Free | View In iTunes |
| 59 | VideoMolecular Simulation of Nanoscale Friction in MEMS | Dr. Chandross has been on the technical staff at Sandia National Laboratories for over 10 years, using large-scale computations to study the aging and reliability of nanomaterials. Prior to joining Sandia he was a National Research Council postdoctoral fellow at SPAWAR San Diego. He holds an M.S. and Ph.D. in physics from the University of Arizona (1996) and a B.S. in physics with electrical engineering from the Massachusetts Institute of Technology (1990). Presented January 30, 2009. | 5/18/09 | Free | View In iTunes |
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The Origins of the Spintronics Revolution (audio only) | Dr. Peter Levy, New York University, is Emeritus Faculty & Professor of Physics. His research is: electrical transport in magnetically layered structures has produced some exciting phenomena; amongst them is the unusually large change in the resistance as the magnetic configuration is realigned from an antiferromagnetic or random in zero field to ferromagnetic at saturation. Known as giant magnetoresistance [GMR] for metallic multilayers and junction magnetoresistance [JMR] for magnetic tunnel junctions, we have been studying the mechanisms that produce this effect. We have adapted extant theories of electrical transport, such as, Kubo's linear response, the Boltzmann equation, and the Landauer approach, to the layered geometries that display this effect. The role of the spin dependent scattering at the interfaces between magnetic and nonmagnetic metals has been identified as the primary source of the GMR in metallic multilayers, while for magnetic tunnel junctions it's the spin dependent density of states at the interface between the magnetic electrode and the insulating barrier. Analytic solutions of the resistivity are found for realistic models of the band structure in the magnetic multilayers. Also, we use the results of ab-initio calculations of the electronic structure that use the coherent potential approximation to account for the effects of the defect scattering to determine the electrical resistivity and GMR of layered structures. Currently, we are studying transport across noncollinear magnetic multilayers and determining the role of spin accumulation in switching the magnetization. The possibility of current induced switching by using polarized currents is an attractive way of resetting magnetic memories. Presented January 16, 2009. | 5/18/09 | Free | View In iTunes |
| 61 | VideoSolar Energy and Photovoltaics | Dr. Simmons is Department Head, Materials Science and Engineering, Professor of Materials Science and Engineering, and Professor of Optical Sciences. His research is in: quantum-size effects in the optical properties of semiconductor clusters; optical properties and carrier dynamics in wide-gap semiconductors; photosensitivity in glass films. Non-linear optical behavior of materials and glasses; optical spectroscopy of materials at the nano-scale level; molecular dynamics simulations; and non-linear viscous flow and rheological behavior of molten glasses. Presented April 16, 2009. | 5/4/09 | Free | View In iTunes |
| 62 | VideoStrong-Field Control of X-Ray Processes, Part II | Dr. Linda Young is an Argonne Distinguished Fellow at the Argonne National Laboratory. Her research interests include atomic, molecular and optical physics; strong-field control of x-ray processes; and ultrafast x-ray imaging. Presented November 14, 2008. | 5/3/09 | Free | View In iTunes |
| 63 | VideoStrong-Field Control of X-Ray Processes, Part I | Dr. Linda Young is an Argonne Distinguished Fellow at the Argonne National Laboratory. Her research interests include atomic, molecular and optical physics; strong-field control of x-ray processes; and ultrafast x-ray imaging. Presented November 14, 2008. | 5/2/09 | Free | View In iTunes |
| 64 | VideoThe Nuclear Force Problem: Is the Never-Ending Story Coming to an End? Part II | Dr. Ruprecht Machleidt is Professor of Physics at the University of Idaho. theoretical nuclear physics; theory of nuclear forces; Chiral effective field theory for low-energy QCD; meson-exchange theories for nuclear interactions; nucleon-nucleon scattering at high energy; theory of nuclear matter with sub-nuclear degrees of freedom and relativity; and relativistic few-nucleon physics. Presented November 17 2008. | 5/2/09 | Free | View In iTunes |
| 65 | VideoThe Nuclear Force Problem: Is the Never-Ending Story Coming to an End? Part I | Dr. Ruprecht Machleidt is Professor of Physics at the University of Idaho. theoretical nuclear physics; theory of nuclear forces; Chiral effective field theory for low-energy QCD; meson-exchange theories for nuclear interactions; nucleon-nucleon scattering at high energy; theory of nuclear matter with sub-nuclear degrees of freedom and relativity; and relativistic few-nucleon physics. Presented November 17 2008. | 5/2/09 | Free | View In iTunes |
| 66 | VideoDesperately Seeking SUSY (Supersymmetry): How Might She Hide At the LHC? | Dr. Everett is Assistant Professor of Physics at the University of Wisconsin, Madison. Her research interests Model-building and phenomenology of physics beyond the Standard Model at and beyond the TeV scale. Specific directions include supersymmetric extensions of the Standard Model, models of supersymmetry breaking, and string phenomenology, with an emphasis on CP violation and flavor physics, cosmological connections, electroweak symmetry breaking and extended gauge sectors, and unified models of fermion masses and mixings. Presented Feb. 13, 2009. | 4/27/09 | Free | View In iTunes |
| 67 | VideoPrecise Electro-Weak Studies, Part II | Dr. Anthony W. Thomas is with the Department of Energy's Thomas Jefferson National Accelerator Facility. His research interests include nuclear physics, nuclear energy, atomic and molecular physics. Presented Nov. 30, 2007. | 4/20/09 | Free | View In iTunes |
| 68 | VideoAre We All Martians? The Meteoritic Exchange of Life between Planets | Dr. H. J. Mehlosh is Professor in the University of Arizona Lunar and Planetary Labs. His research interests include theoretical geophysics and planetary surfaces. Presented Feb. 24, 2009. | 4/20/09 | Free | View In iTunes |
| 69 | VideoPrecise Electro-Weak Studies, Part I | Dr. Anthony W. Thomas is with the Department of Energy's Thomas Jefferson National Accelerator Facility. His research interests include nuclear physics, nuclear energy, atomic and molecular physics. Presented Nov. 30, 2007. | 4/20/09 | Free | View In iTunes |
| 70 | VideoFields Available at the Intergalactic Magnetic Lab | Abstract: This talk will provide a brief survey of some of the most important, and sometimes dramatic, physical phenomena that occur in organic conductors and superconductors in the presence of high magnetic fields. Magnetic field induced superconductivity, quantum interferometry, magnetic field-induced phase transitions, and of course Lebed's magic angle effects, will be among the topics of this presentation. Presented April 6, 2007. Prof. Brooks received his Ph.D. in Physics from the University of Oregon in 1973. He is part of the BT&T Molecular Crystal Group. Research activities of the BT&T include the experimental and computational investigation of fundamental mechanisms in low dimensional and anisotropic materials, including both organic and inorganic molecular conductors. | 2/8/09 | Free | View In iTunes |
| 71 | VideoSingle-Molecule Electronic Properties | Dr. Natelson is Associate Professor of Physics and Astronomy, Associate Professor in Electrical and Computer Engineering, and Fellow, at Rice Quantum Institute in Houston, Texas. His research group focuses on the electronic, magnetic, and (recently) optical properties of nanoscale structures. Over the last ten to twenty years there has been tremendous progress in the ability to manipulate matter at levels approaching the atomic scale. By constructing model nanosystems (nanoparticle, nanowires, atomic-scale junctions, transistors with individual molecules as the active region), we are able to examine the basic physics that becomes relevant at these scales. He presented on September 26, 2008. | 2/8/09 | Free | View In iTunes |
| 72 | VideoWhy is Quark-Gluon Plasma A Perfect Liquid? | Abstract: My lecture will describe what is now known from experiments about the properties of strongly interacting matter at the highest accessible energy densities. The important pieces of evidence include: large collective flow, strong quenching of jets, and characteristic differences in the emission features of mesons and baryons. The matter produced in nuclear collisions thus reveals itself as a nearly inviscid fluid ("perfect liquid") of extreme SU(3)-color opaqueness. I will explain how these properties are related to each other and discuss what they may imply for the internal structure of the matter produced at RHIC. The lecture will conclude with a brief discussion of the main open questions to be addressed in future experimental and theoretical investigations. Presented April 20, 2007 Dr. Mueller is J. B. Duke Professor of Physics at Duke University. Dr. Mueller's research currently focuses on nuclear matter at extreme energy density. Quantum chromodynamics, the fundamental theory of nuclear forces, predicts that nuclear matter dissolves into quarks and gluons, the constituents of nucleons, when a critical energy density is exceeded. He and his collaborators are studying the properties of this quark-gluon plasma from the theoretical point of view. They are also developing the theory of the formation of a quark-gluon plasma and its possible detection in high-energy nuclear collisions. | 2/8/09 | Free | View In iTunes |
| 73 | VideoThe Wonders of Supersymmetry: From Quantum Mechanics, Topology, and Noise to (maybe) The LHC | Abstract: Supersymmetry is a quantum-mechanical symmetry relating bosons and fermions. It was discovered more than 35 years ago in quantum field theory and string theory, but the seeds of its ``miraculous" properties can be seen already in quantum mechanics. This talk introduces supersymmetry via the supersymmetric (an-)harmonic oscillator. We shall see that this seemingly trivial example is sufficiently rich to allow us to illustrate how supersymmetry is used in a variety of fields: from mathematics and elementary particle physics to critical phenomena and stochastic dynamics. Presented Jan. 18, 2008. Dr. Erich Poppitz is Professor of Physics, the University of Toronto. His research interests in physics go beyond the standard model. He also studies general quantum field theories and their non-perturbative dynamics, using a variety of tools, from supersymmetry, branes, and dualities, to lattice field theory and Monte-Carlo simulations. | 1/28/09 | Free | View In iTunes |
| 74 | VideoAttosecond Science | Dr. Schafer is a theoretical AMO physicist who specializes in strong field physics. The name "strong field physics'' refers to the interaction of intense, ultrafast laser pulses with atomic and molecular systems. Strong field physics takes place in the interesting regime where the electron-ion and electron-laser interactions are of competing strengths. This gives rise to a host of time-dependent and highly non- linear phenomenon such as above threshold ionization, high harmonic generation, sequential and non-sequential multiple ionization of atoms and molecules, and x-ray production from clusters, which are characterized both by rapid ionization and the coherent interaction of the ionizing electron with the parent atomic or molecular ion. His current research centers on the theory of intense laser-matter interactions with an emphasis on the generation and application of attosecond pulses. An attosecond is 1/1000 of a femtosecond, and attosecond sources are the shortest light pulses ever made. Since attosecond pulses were first measured in 2001, the growth of "attoscience" has been exponential, spurred by the potential these pulses have for imaging and controlling electron motion. Our research group, consisting of myself and Mette Gaarde, has the unique capability to investigate all phases of the attosecond pulse generation process, from the microscopic single atom interaction to the macroscopic propagation and phase matching of the emitted radiation. The research is interdisciplinary, combining atomic and optical physics, and centered around high performance computing for non-perturbative solutions of both the time- dependent Schroedinger equation and the Maxwell wave equation. The research is highly relevant to experiment and we have active collaborations with several of the leading experimental groups pursuing attosecond science. We are involved in all phases of the experimental work, both as interpreters of results and as partners in designing new experiments. Lecture presented Dec. 15, 2008. | 1/26/09 | Free | View In iTunes |
| 75 | VideoDynamics of Membrane Proteins Studied by Solid-State NMR Relaxation | Dr. Brown's research activities include: Nuclear magnetic resonance (NMR) is the most widely used spectroscopic method in chemistry and biochemistry – there many applications and research opportunities. Applications range from organic synthesis to protein structure elucidation in solution and fibrils or membranes, and to magnetic resonance imaging (MRI) of human subjects. Apart from its remarkable breadth and versatility, a unique feature of NMR is the ability to provide information about both structure and dynamics. Our research entails the development of NMR techniques through applications to materials science and biomolecular systems. A cross-disciplinary approach is taken to relate the properties of materials and molecular structure to function. Currently, we are actively engaged in research in several interrelated areas. Our aims in spectroscopy and analytical methods entail development and application of NMR methods to liquid-crystalline materials and biomolecular systems. In the area of biophysics, we are conducting structural studies of membrane proteins and membrane lipids. A common theme is to illuminate material or biochemical properties using molecular structural methods that advance our mechanistic understanding for applications. A range of chemical, physical, analytical, and biochemical methods are used, and provide the opportunity for broad-based cross-disciplinary training. Presented October 3, 2008. | 1/23/09 | Free | View In iTunes |
| 76 | VideoDirect and Indirect Searches for Particle Dark Matter (The discovery era begins) | Dr. Hooper is a scientist in the Particle Physics Division/Astrophysics Physicists at the Fermi National Accelerator Laboratory, and an Assistant Professor in the Department of Astronomy and Astrophysics at the University of Chicago. Previously, he was the David Schramm Fellow at Fermilab, and a postdoc at the University of Oxford. In 2003, he completed my Ph.D in physics at the University of Wisconsin. His research focuses on the interface between particle physics and cosmology. He is especially interested in questions about dark matter, supersymmetry, neutrinos, extra dimensions and cosmic rays. For a complete list of my scientific publications, see the SPIRES archive. Presented on September 12, 2008. | 1/23/09 | Free | View In iTunes |
| 77 | VideoThe New Frontier of Computational Science: Applications to High Leverage Decisions | Dr. Kusnezov is Reseach Scientist at Yale University. | 12/9/08 | Free | View In iTunes |
| 78 | VideoThe Advanced X-ray Timing Array (AXTAR) | -- | 12/8/08 | Free | View In iTunes |
| 79 | VideoA Neutrino Perspective on the Universe | -- | 12/8/08 | Free | View In iTunes |
| 80 | VideoFrom the Big Bang to Dark Matter: Turning on the Large Hadron Collider | On September 10 , the Large Hadron Collider began operation by sending a beam of sub-atomic particles around a 17-mile underground tunnel beneath the boundary of France and Switzerland. Ultimately the experiment will provide fundamental discoveries about our universe. Dr. Elliott Cheu Professor of Physics discussed the UA's participation in the historic experiment and explained how the world’s largest scientific instrument will reveal secrets about our world. Robert Shelton, UA President and Professor of Physics, gave the welcome. Presented September 10, 2008. Dr. Cheu's current research topics include searches for CP violation and physics beyond the Standard Model. This work is being carried out at the D0 experiment at the Fermilab National Laboratory and the ATLAS experiment at CERN. The D0 experiment is currently recording data at the world's most powerful accelerator. With the data samples we expect to collect, we should be able to significantly improve our sensitivity to new physics. The ATLAS experiment represents the next generation of particle physics experiments and may provide the first clear indications of physics beyond the Standard Model. | 12/8/08 | Free | View In iTunes |
| 81 | VideoEffective Field Theory & Strongly Interacting Systems: Charmed Hadrons to Cold Atoms | Dr. Thomas Mehen is an Associate Professor in Duke University's Department of Physics. Prof. Thomas Mehen works primarily on Quantum Chromodynamics (QCD) and the application of effective field theory to problems in hadronic physics. Effective field theories exploit the symmetries of hadrons to make model independent predictions when the dynamics of these hadrons are too hard to solve explicitly. For example, the properties of a hadron containing a very heavy quark are insensitive to the orientation of the heavy quark spin. Prof. Mehen has used this heavy quark spin symmetry to make predictions for the production and decay of heavy mesons and quarkonia at collider experiments. Another example is the chiral symmetry of QCD which is a consequence of the lightness of the up and down quarks. The implications of this symmetry for the force between nucleons is a subject of Prof. Mehen's research. Prof. Mehen has also worked on effective field theory for nonrelativistic particles whose short range interactions are characterized by a large scattering length. This theory has been successfully applied to low energy two- and three-body nuclear processes. Some of Prof. Mehen's work is interdisciplinary. For example, techniques developed for nuclear physics have been used to calculate three-body corrections to the energy density of a Bose-Einstein condensate whose atoms have large scattering lengths. Prof. Mehen has also worked on novel field theories which arise from unusual limits of string theory. Examples include noncommutative field theories and theories of tachyonic modes on non-BPS branes. Presented Feb. 29, 2008. | 12/8/08 | Free | View In iTunes |
| 82 | VideoThe Problem of Motion: It's Not Just Academic, it's Astronomy | Consider one of the most rudimentary problems in physics. Drop a mass (m) at rest from a height (d) above the surface of the earth, and calculate its position as a function of time y(t). The solution y(t)=d-frac{1}{2} g t^2, taught in freshman physics is an excellent approximation to the solution. Suppose, however, that we wish to be more exact. There are multiple sources of corrections to this solution. Standard ideas in general relativity allow one correct for relativistic effects. However, a closer look reveals that there exist many more complications. For instance, the mass will not be point-like, and will radiate gravitational waves. It will also deform under the influence of the gravitational field. These effects are intertwined, and their inclusion can make the problem of solving for the trajectory intractable. In the past, solving this problem was only of academic interest, but now our ability to distinguish between astrophysical objects in the next generation of gravity wave detectors will rely upon its solution. In this talk, I will discuss how one can use ideas developed for statistical mechanics and quantum field theory to solve this ``problem of motion'' in a systematic fashion. Presented October 19, 2007. | 12/8/08 | Free | View In iTunes |
| 83 | VideoLarge, Room-temperature Magnetoresistance in Organic Light-Emitting Diodes | We report on the discovery and experimental characterization of a magnetoresistive effect in organic light-emitting diodes with a magnitude of up to 10% at room temperature for small magnetic fields, B = 10mT. Its discovery came as a surprise since it has often been believed that large magnetoresistance at room-temperature requires magnetic materials. We show that the effect is caused by the interaction between paramagnetic carriers. These interactions obey spin-selection rules that are sensitive to the presence of nuclear magnetic fields. We will also describe possible applications of the effect. Presented October 26, 2007. | 12/8/08 | Free | View In iTunes |
| 84 | VideoHow Does the Spin-polarized Current Manipulate Magnetization States of Nano-magnets? | Today's forefront technological applications of magnetic materials are based on control and manipulation of magnetization on the scale of nanoseconds and nanometers. The convention method of using a magnetic field to write magnetization states has encountered increasing difficulties. Recently, a novel scheme based on spin-polarized current-driven magnetization switching has emerged as a most promising alternative for faster and denser magnetic technology. In this talk, I will discuss why and how a spin-polarized current interacts with the magnet from the principle of spin angular momentum conservation. Then I will present our recent work in understanding current-driven domain wall motion, distortion, and spin-wave excitations in a magnetic nanowire. Presented September 14, 2007. | 12/8/08 | Free | View In iTunes |
| 85 | VideoWhat Does the Electric Field Look Like Inside A Complex Laser Cavity? | The nature of the electric field in a laser well above threshold has been a long-standing question in laser theory, complicated by the difficulty of treating exactly both the non-linear interaction and the openness of a laser cavity. With the advent of complex lasers, such as random, wave-chaotic and photonic bandgap lasers, this mathematical challenge has become of great relevance. I will discuss recent results emerging from an extension of semi-classical laser theory to open systems with a high degree of spatial complexity in the linear (passive cavity) regime. Certain concepts and methods that has been originally devised for disordered/chaotic electronic systems will be shown to be highly effective in describing spatio-temporal phenomena in complex lasers. Presented August 31, 2007. | 12/8/08 | Free | View In iTunes |
| 86 | VideoCat States in Ultracold Atoms | It is vital not to take our most fundamental physical theories for granted. For example, researchers have looked for deviations from the gravitational inverse square law at very small sub-micron length scales. Similarly, one can ask what predictions of quantum mechanics might break down in untested regimes. Since the classical world is macroscopic and the quantum world is microscopic, a natural place to test quantum mechanics is in mesoscopic physics. Macroscopic superposition is a largely untested mesoscopic prediction of quantum mechanics. An excellent candidate for macroscopic superposition states, also called Cat (or NOON) States after Schrodinger's famous gedanken experiment, is a Bose-Einstein condensate in a double well. Mathematically, this is a fifty year old quantum many body problem. The experimental context of Bose-Einstein condensates gives one hope to observe the first truly large scale Cat States of matter. We show that Bose-Einstein condensates require two new energy scales. We introduce the role of the dimensionality of each well. We demonstrate that the many body wavefunction serves to protect Cat States from decoherence. Finally, we present a practical scheme for dynamic realization of such states. Presented October 12, 2007. | 12/8/08 | Free | View In iTunes |
| Total: 86 Episodes |
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