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Physics & Astronomy Colloquium
Thursdays, 3:30 p.m.
P.S. 306
Call us at: (323) 343-2100
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Winter Quarter 2010 Schedule

Physical Sciences Building, P.S. 306
Refreshments - 3:15 p.m., Colloquium - 3:30 p.m


Pizza Party
CSULA Faculty Research


Alexander L. Rudolph
Professor of Physics, Cal Poly Pomona

     "The Effect of Interactive Instruction in the Astro 101 Classroom:
Report on a National Study"

We have conducted a national research study designed to determine the effect of interactive learning strategies on students' conceptual learning in general education astronomy courses (Astro 101).   Nearly 4000 students at 31 institutions, (4-year and 2-year) around the country participated in the study.   Our results show dramatic improvement in student learning with increased use of interactive learning strategies independent of institution type or class size, and after controlling for individual student characteristics.  In addition, we find that the positive effects of interactive learning strategies apply equally to men and women, across ethnicities, for students with all levels of prior mathematical preparation and physical science course experience, independent of GPA, and regardless of primary language.  These results powerfully illustrate that all categories of students can benefit from the effective implementation of interactive learning strategies.  The presentation will make use of Classroom Response Systems (aka "clickers") allowing participants to experience interactive learning firsthand.


Dr. K. I. Kugel
Institute for Theoretical and Applied Electrodynamics
Russian Academy of Sciences

     "Magnetic Inhomogeneities in Materials with Spin-state Transitions"

Spin-state transitions are observed in many transition metal compounds, e.g. in those containing Co 3+ and Fe 2+ . Such transitions may occur with the change of temperature, pressure, and also with doping, in which case the competition of single-site effects and kinetic energy of doped carriers can favor a change in the spin state. To deal with this situation, we consider a simple model similar to that used for manganites [1] involving two kinds of strongly correlated charge carriers, localized and itinerant. Based on such a model, we predict the possibility of a jump-like change in the density of itinerant charge carriers accompanied by the change in the spin state of cobalt ions at a certain doping level. A tendency to the electronic phase separation within a wide doping range is demonstrated. Phase diagrams with the regions of phase separation are constructed at different values of the characteristic parameters of the model [2].

[1] K.I. Kugel, A.L. Rakhmanov, and A.O. Sboychakov, Phys. Rev. Lett. 95 , 267210 (2005)
[2] A.O. Sboychakov, K.I. Kugel, A.L. Rakhmanov, and D.I. Khomskii, arXiv:0904.4760 (2009)


Dr. Rachel Akeson
California Institute of Technology/Jet Propulsion Laboratory

     "Infrared Interferometry and the Evolution of Circumstellar Disks"

After a brief review of the current state of infrared interferometry, particularly the Keck Interferometer, I will focus on observations of circumstellar disks around young and main sequence stars. Infrared interferometry is unique in its ability to make direct, milli-arcsecond scale measurements of the physical properties of the central regions of these disks. These measurements have placed strong constraints on the inner disk regions of T Tauri and Herbig stars. More recently, this technique has also been applied to the so-called transitions disks and the debris disks around main sequence stars.


Dr. Jiyeong Gu
California State University, Long Beach

"The Proximity Effect in Superconductor/Ferromagnet Hybrid Systems"

Recent technological advances made it possible to create hybrid nano-structures with high quality ferromagnet/superconductor (F/S) interfaces. The F/S systems have been in focus of intensive experimental and theoretical studies because of both exciting fundamental problems and potential device applications. The physical properties of both F and S films are strongly modified near the interface due to mutual proximity effect, for example, superconducting correlations penetrate into F and the spin polarization can extend into S. I will show an overview of experimental observations and theoretical predictions of F/S proximity effects including superconducting switching effect in F/S/F trilayer. I will then describe my group's recent research on the exchange-spring/ superconductor hybrid system. In exchange-coupled hard/soft bilayer systems, the mutual coupling of the soft and hard magnetic layers creates a spiral magnetic domain structure. We utilized the exchange-coupled hard/soft bilayer system, such as NiFe/SmCo or NiFe/SmFe, to vary the magnetic environment near the superconducting layer. The superconducting property of the hybrid system was investigated as functions of the temperature and magnetic field.


Dr. Deborah Padgett
California Institute of Technology/Jet Propulsion Laboratory

     "The Wide-field Infrared Survey Explorer (WISE) "

Wide-area infrared surveys are revolutionizing our knowledge of cool and dusty objects in and beyond our galaxy. Starting with the IRAS mission in the 1980s, a series of space telescopes have mapped the sky at mid-to-far infrared wavelengths, while ambitious surveys from the ground such as 2MASS, DENIS, and UKIDSS have done the same at near-infrared wavelengths. During the past six years, the Spitzer Space Telescope has performed a number of Legacy surveys at exquisite sensitivity for much of the Galactic Plane, nearby star-forming clouds, and a few deep extragalactic fields.  However, they cover only a small fraction of the entire sky. In order to find the brightest examples of rare sources such as solar neighborhood cool brown dwarfs and the most luminuous galaxies in the universe, all sky coverage is required. The Wide-field Infrared Survey Explorer (WISE) which launched Dec. 2009, is currently mapping the entire sky at 3.3, 4.7, 12, and 22 microns with high sensitivity. WISE will provide source lists for detailed studies of individual infrared objects at high resolution and sensitivity with the next generation of powerful infrared telescopes such as JWST. In this talk, I will discuss the WISE mission, show some of its latest results, and explore the range of opportunities to harvest the pick of the crop of cool and dusty objects revealed by large infrared surveys.


Dr. Daniel Arovas
University of California, San Diego

"What Can We Learn from Quantum Entanglement?"

Quantum entanglement is a concept which has been applied in astrophysics, condensed matter physics, and quantum information theory.  In addition to the notion of entanglement entropy, in recent years it has been appreciated that the whole "entanglement spectrum", i.e. the eigenspectrum of the reduced density matrix, can provide an even more detailed picture of the entanglement properties of a many body quantum state.  I will discuss examples from condensed matter physics, culminating in a description of recent work on the entanglement spectra of quantum spin chains.


Dr. Prasanth Jaikumar
California State University, Long Beach

     "Fossil Neutron Stars as Fuels for Nucleosynthesis"

The origin of neutron-rich stable nuclei and isotopes beyond the iron group (mass number A>90) is connected with the astrophysics of Supernovae and Neutron stars. Supernovae have been extensively studied in this regard, and are known to make neutron-rich heavy elements via the r-process (rapid neutron capture). But an outstanding problem remains: do the initial conditions provide enough neutrons to match the observed abundances of r-process elements? I will discuss the much less studied role of Neutron stars in Nucleosynthesis. Decompressing neutron matter from the surface of neutron stars can provide the requirements for heavy element production: neutron-rich seeds and a large neutron-to-seed ratio. The results of our astrophysical simulations of decompressing neutron matter will be compared to recent data on r-process abundances in old metal-poor stars and light curves of superluminous supernovae, suggesting that Neutron star evolution plays a key role in the origin of elements.

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