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Colloquia & Seminars, Fall 2008

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Some Frontier Problems of the XXI-Century Physics

Speaker:Professor Efrain J Ferrer
Date: November 7, 2008 (Friday)
Time: 4 p.m.
Room: 205 Currens Hall

Abstract
In this colloquium, I will discuss some of the fundamental challenges faced by the physics at the beginning of the XXI Century. The role of Supersymmetry in Cosmology and Astrophysics, the problem of Dark-Energy, Extra-Dimension issues, among others, will be addressed at a general level. The colloquium is intended to motivate the students to become involved in the great discovering adventures of the XXI Century.

About the speaker:
Professor Efrain J Ferrer is a physics professor from the Western Illinois University. His research concerns theoretical high-energy physics under external conditions (finite temperature and densities, magnetic and electric fields, nontrivial topologies, etc.)

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Optically polarized NMR in semiconductors

Speaker:Dr. Kannan Ramaswamy
Date: November 14, 2008 (Friday)
Time: 4 p.m.
Room: 205 Currens Hall

Abstract
Decades ago, it was experimentally demonstrated that it is possible to polarize the electron spins in a semiconductor through irradiation with light. The extent to which the electrons can be polarized depends on the details of the band structure, the optical selection rules, the relaxation processes and various other external factors such as temperature and magnetic field. The oriented electrons interact with the nuclear spins through hyperfine interaction resulting in nuclear spin polarization. Furthermore, the enhanced nuclear polarization that can be achieved in semiconductors by this method extends its utility to interrogate interesting physics exhibited by low dimensional semiconducting systems such as quantum wells, quantum wires or quantum dots where there is less number of nuclear spins available for detection. The optically generated nuclear spin polarization can be detected by optical techniques (ODNMR) or by direct radio-frequency technique known as optically polarized NMR (OPNMR). I will present 69/71Ga OPNMR investigations in semi-insulating GaAs. Specifically I will emphasize on our recent experimental findings related to the hyperfine shift of the OPNMR spectra which lead to a fundamental understanding of the phenomenon of optically generated nuclear spin polarization in semiconductors. I will also discuss intuitive models, we have developed, which explains the dependence of nuclear spin polarization on various parameters such as photon energy, helicity /intensity of light and magnetic field.

About the speaker:
Dr. Kannan Ramaswamy is a Research Scientist from Washington University, St. Louis. His research focuses on applying optical pumping techniques to systems of semiconductors to better understand their opto-electronic properties.

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Modeling Matter at Extreme Conditions: Simulations of the Ions in Neutron Star Crusts and Supernovae

Speaker:Dr. Liliana Caballero
Date: November 21, 2008 (Friday)
Time: 4 p.m.
Room: 205 Currens Hall

Abstract
Several phenomena in Supernovae and Neutron Stars (NS) depend on the behavior of the highly dense plasma formed during the core collapse and present in the NS crust. Correlations between the ions in this highly dense plasma have a tremendous impact on neutrino trapping during the collapse and on transport properties in the NS crust. I shall discuss the use of Molecular Dynamics simulations to study the behavior of ions under conditions of extreme density and show results obtained for transport properties such as the thermal conductivity and the viscosity.

About the speaker:
Dr. Liliana Caballero is a post-doctoral research associate at the Department of Physics, North Carolina State University. Her research focuses on theoretical astrophysics.