================================================================== Physics & Astronomy Seminars at Univ. Louisville, Spring 2009 till Spring 2009: Caty Pilachowski, Indiana U 09 Jan 2009 - no talk 16 Jan 2009 - Jim Lauroesch, UL "An Optical/UV View of Interstellar Small Scale Structure" Optical spectra reveal that absorption line components change in strength, velocity, and even number from sightline to sightline. Such studies provide convincing evidence for pervasive small-scale structure in the diffuse interstellar medium on scales of order 1000 AU through observations of members of multiple star systems and clusters. However, these variations do not imply that the interstellar medium consists of a multitude of very small cloudlets since the majority of components are seen toward all stars in a system. Instead it appears that these variations arise in what appear to be "sheets" of gas within which the physical conditions vary. Using temporal variations in interstellar absorption lines it has been found that in some cases there can be significant structure on scales as small as ~10 AUs. Recent results for specific clouds will be discussed, as well as plans for the near future. 23 Jan 2009 - Susan Gardner, U Kentucky (host Morrison), subject: dark matter(?) "Shedding Light on Dark Matter" Disparate astronomical observations provide compelling evidence for additional, non-luminous matter, or dark matter, in gravitational interactions, but we know little of its nature. To remedy this, the hunt is on to detect dark matter via either direct or indirect means and to determine its properties. I will review the astronomical evidence and summarize current detection efforts before describing a new possibility, namely, of searching for dark matter with a magnetic moment using light-dark matter interactions. 30 Jan 2009 - Romaneh Jalilian, Purdue (host Yu) - postponed to next week due to ice storm 06 Feb 2009 - Romaneh Jalilian, Purdue (host Yu) "Pulse Laser Assisted Growth of Nanowires and their Properties" Nanotechnology as one of the leading sciences of the century is an ensemble of growth, characterization and device fabrication of nano-size structures. Nanomaterials are the new generation of electronic and optoelectronic devices building blocks. Therefore, it is essential to investigate the structure, composition and functionality of these materials. Here, growth of self-catalyzed binary, ternary and quaternary alloyed nanowires is reported. These nanowires are synthesized using pulsed laser vaporization without any foreign catalyst. The ablation on a solid target produces a plume of the atomic species of the respective compound of the target in vapor phase along with the formation of liquid metallic particles (e.g. Ga or In). Absorption and saturation of the target components in the molten droplets and creation of hillocks provide nucleation centers thereby precipitating crystalline nanowire at these lower energy sites. High resolution transmission electron microscopy on the synthesized material reveals crystalline and superlattice structured (often twinned) nanowires. Detailed characterizations have been performed using SEM, TEM, EDS, and Raman spectroscopy. This growth technique provides the means of growing III-V alloy nanowires with varying compositions suitable for optoelectronic devices. Combined effect of local heating and thermal expansion with phonon confinement has been studied initially for Ge nanowires via Raman spectroscopy studies and subsequently extended to model the binary, ternary and quaternary III-V semiconducting nanowires. 13 Feb 2009 - Viktor Henner, Perm & UL "Wavelet Analysis (WA): introduction and some applications" The WA appeared as result of a demand to analyze data which Fourier analysis (FA) couldn't successfully manage. Because of non-locality of trigonometric functions, the information obtained with FA is completely delocalized among all spectral coefficients. Random singularities in data affect all Fourier coefficients. WA allows us to extract high frequency information from relatively short intervals, and low frequency information from wide time intervals, thus providing an optimal compromise with the uncertainty principal. WA is robust to noise and is used for studying local structures or for analysis of spectral properties. Some applications will be briefly presented. 20 Feb 2009 - Hossein Sadeghpourgs, Harvard/SAO (Morrison) "Cooling and Trapping of Strongly Magnetized Rydberg (anti)hydrogen" The first neutral antimatter was created a few years ago, but much needs to be done before an antihydrogen atom and a hydrogen atom could be compared side by side. Frist, the anti-atoms are made into high Rydberg states, so they must cooled to the ground state. Second, they exist in strongly magnetized environments, so the magnetic field is not a perturbation. Third, they must be translationally cold so that they could be trapped for comparative analysis. In this talk, I will picture a theorist's angle on how these steps could be achieved. 27 Feb 2009 - David Latimer, UK (ex-UL) (Host Williger) "A cosmic index of refraction" A concordance of observations point to the fact that an overwhelming majority of the matter in the universe consists of non-baryonic dark matter. Despite its preponderance, little is known about its nature. Experiments are underway in an attempt to detect dark matter both directly and indirectly. I will review this search and then discuss another possible way to constrain dark matter properties--through its interaction with light. The dark-matter candidates of particle physics typically possess electromagnetic interactions, if only via quantum fluctuations. Taken en masse, dark matter can thus engender the cosmos with a dispersive index of refraction. From this cosmic index of refraction, observational limits on dispersive effects can in turn be used to limit the particle properties. General considerations inform the expansion of the index of refraction with frequency. I will discuss these, the physical interpretation of the terms, and the particular observations needed to isolate its coefficients. 06 Mar 2009 - Justin Vandenbroucke, UC Berkeley (host Brown) "IceCube: a billion-ton telescope at the South Pole" Neutrino astronomy is a new field combining astrophysics and particle physics. Detecting (or not detecting) neutrinos from gamma-ray bursts and active galactic nuclei will be an essential piece of understanding what they are and how they work. Neutrinos may also tell us the nature of dark matter and the origin of cosmic rays. IceCube, a neutrino telescope under construction at the South Pole, exploits the crystal-clear ice located a mile deep in the ice at the South Pole to detect flashes of light produced by high-energy neutrinos. The detector will span a cubic kilometer (a billion tons) of ice. Two- thirds complete, IceCube is already producing exciting data we are busy analyzing, and the first results have been published. I will describe the science and technology of IceCube and show photos of life and science at the South Pole. I will focus in particular on a new idea we are investigating, to literally listen for the acoustic signals produced by neutrinos hitting the ice. 13 Mar 2009 - Varsha Kulkarni, USC (host Lauroesch) "Shadows of Galaxies: Quasar Absorption Line Systems as Probes of Galaxy Evolution" The evolution of galaxies and the cosmic history of element production are fundamental themes in modern astrophysics and cosmology. Absorption lines in quasar spectra can be used to probe interstellar gas in galaxies at various stages of evolution, and thus provide powerful probes of the history of star formation and chemical enrichment in galaxies. In spectroscopic studies with the Hubble Space Telescope (HST) and several ground-based telescopes, we have significantly expanded measurements of chemical composition of absorber galaxies at redshifts z < 1.5. These studies suggested a "missing metals problem" for the most gas-rich absorber galaxies, i.e. the damped Lyman-alpha absorbers (DLAs), in apparent contradiction with the predictions of cosmic chemical evolution models. On the other hand, we have discovered a population of sub-damped Lyman-alpha absorber galaxies that are highly metal-rich. These metal-rich sub-DLAs appear to be kinematically and chemically different from typical DLAs, suggesting that they may be a distinct population. We will discuss the role of these metal-rich objects in the cosmic metal budget. We also discuss the challenges in detecting galaxies producing the absorption lines, and describe observations aimed at imaging the absorber galaxies, using the HST and adaptive optics imaging on large ground-based telescopes. We will describe attempts to detect the absorbing galaxies in emission lines to probe their star formation rates. Finally, we will discuss implications of the absorbers for galaxy properties and evolution. 27 Mar 2009 - Mike Sitko, U Cincinnati (host Kielkopf) "Variability of the Inner Dust Structure in PMS Disk Systems" During the past decade, great progress has been made in understanding the the planet-building disks of gas and dust that surround young stars. While most current models treat these systems as relatively steady-state, recent observations indicate that they are anything but. A decade-long program has revealed variability in the 1-5 micron emission in pre-main sequence disk systems that demonstrates that they are highly dynamic, and this may eventually prove useful for determining the physics of the inner disk systems, and whether planetary perturbations of the disk, or other mechanisms, are operating. The variations in HD 31648 (MWC 480) and HD 163296 (MWC 275) are greatest near 3 microns, and the associated temperatures indicate that the variation must be occurring near the dust sublimation zone (DSZ) - the innermost wall of the dust disk. For HD 163296, changes in the location of the DSZ are confirmed by near-IR Interferometry, and these may be related to changes in the appearance of the outer disk seen in scattered light. DG Tau exhibits variations in its silicate band consistent with material being lofted above the disk. The inner dust belt in the transition disk system SAO 206462 is also variable, and may signal the presence of collisions within 1 AU of the star. The implications for observational programs as well as modeling efforts will be discussed. 03 Apr 2009 - James Lewis, West Virginia (host Yu) "What Can Frontier Orbitals in Disordered Systems Tell Us about the Properties of a Material?" Fundamental understanding of the properties of materials will lead to innovation in terms of their applications in several areas including electronics, optics, catalysis, etc. Both experimental and computational characterization of these materials are critical to understanding properties and subsequent applications. Electronic structure methods probe information about the electronic states from which properties of materials can be understood from an electron's point of view. Exploring 'frontier orbitals' (i.e. molecular orbital states or electronic states near the valence band edge) can reveal a lot about a material and its suitability for a targeted application. An added difficulty in potential nanoscience applications is that small leads to disorder (especially for biomolecules), and this disorder adds an extra dimensionality to the frontier orbital picture. Hence, the potential application is not so clear as for a bulk material. We will discuss our work exploring these frontier orbitals in a variety of systems, including biomolecules and inorganic, and discuss the implications for each system. 10 Apr 2009 - Honors Colloq, Su-Huai Wei, Theoret. Matl Sci Grp Natl Renewable Energy Lab, Golden CO (host Wu) NS112 "First-Principles Design of Functional Materials for Energy Applications" Materials design using first-principles techniques is one the ultimate goals in computational materials science. Due to the recent advancement in first-principles electronic structure theory and computing power, it is now possible to perform knowledge-based computational design of materials with unique optical, electrical, or magnetic properties that are tuned to specific energy related applications. This vital tool, therefore, has the great potential to accelerate scientific discovery. In this talk, selective recent works from my group will be discussed to illustrate how computational methods can be used to design functional materials. These include (i) Absorber materials through cation mutation for solar cells, (ii) n-type, p-type or bipolarly dopable transparent conducting oxides (TCO) for optoelectronic devices. (iii) Defect complexes that has shallow donor or acceptor levels. (iv) Filled tetrahedron nitride compounds for solid state lighting applications. (v) Low band gap oxides for photoelectrochemical hydrogen production through water splitting. 16 Apr 2009, Frank Wilczek, Andrew Chamblin Mem. Lecture (not available for 17 Apr as he is giving a talk at U. Kentucky) 17 Apr 2009 - Mel Ulmer (host Lauroesch) "Rapture of the Deep Sky" Astronomers have become "drunk" like deep sea divers with observations of the deep (faint object) sky. This has lead to a host of telescopes that enable us to see fainter and fainter than ever before. The majority of astronomers have focused on finding the most distant objects, but exciting science can be done by going fainter besides pushing to the edges of the Universe. I will show how I have taken advantage of the ability to detect faint sky objects to study clusters of galaxies. These are exceedingly interesting objects that allow us to engage some of the key issues of physics today, such as Dark Energy and Cold Dark Matter (CDM). Clusters are also natural places to learn about the origin and evolution of both galaxies and the large scale structure of the Universe. I will describe how clusters can be a used to address the nature of Dark Energy as well as what clusters already have to say about Dark Matter FUTURE SPEAKERS: other interesting seminars 6.) Optical Imaging lunch seminar Brad Taylor, PhD, from Caliper Life Sciences, will update us on "In Vivo Biophotonic Imaging: Discovery at the Speed of Light," Tuesday, Jan. 29, 11:45 a.m-1 p.m. in room B-038, Baxter II. Applications with optical imaging are on a rapid steady rise, please come to feel the excitement. Panera Bread box lunch will be served; first come, first served. (Submitted By: Chin Ng, Radiology) POSTPONED from 21 Mar 08 Nandini Trivedi, Ohio State (host Jayanthi), Bose-Einstein Condensation, Superconductivity, Quantum-Hall Effect from 06 Feb 2009 - Tiziana di Matteo, CMU (host Williger) after Feb 2009: contact Anna Frebel, will be at CfA from 27 Feb Brian Dennison, UNC-Asheville (host Kielkopf) from 13 Mar: Dave Bowen (Princeton) seminar contact at UK: Moshe Elitzur