Physics Colloquium - Fall 2015

Speaker: John Salzer, Astronomy Department, Indiana University Bloomington

Abstract: I describe the H-Alpha Dot Survey, an ongoing program that utilizes narrow-band images taken for other purposes to discover a population of faint emission-line sources. While the H-alpha Dots appear to represent a random assortment of extragalactic systems, they are in fact a highly differentiated collection of strong-lined galaxies at a range of redshifts. I give examples of how the H-Alpha Dots can be used to explore a number of important problems in modern astronomy.

Speaker: Gung -Min Gie, Department of Mathematics, University of Louisville

Abstract: In fluid mechanics, it is the interaction of the fluid with the boundary that is most critical to understand the behavior of fluids inside a bounded region. Some interesting applications include analyzing, e.g., the motion of air around airplanes or automobiles to increase the efficiency of motion, the flow of atmosphere and oceans to predict the weather, and the blood flow inside blood vessels in medicine where the fluid, such as air, water, or blood is considered incompressible and very little viscous. In this talk, we discuss some recent approaches of analysis and computations in this research direction.

Speaker: Bharat Ratra, Kansas State University

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

Speaker: Hal Weaver, New Horizons Project Scientist Johns Hopkins University / Applied Physics Laboratory

Abstract: The New Horizons (NH) mission was selected by NASA in November 2001 to conduct the first in situ reconnaissance of Pluto and the Kuiper belt. The NH spacecraft was launched on 2006 January 19, received a gravity assist from Jupiter during closest approach on 2007 February 28, and flew 12,500 km above Pluto's surface on 2015 July 14. NH carried a sophisticated suite of seven scientific instruments, altogether weighing less than 30 kg and drawing less than 30 W of power, that includes panchromatic and color imagers, ultraviolet and infrared spectral imagers, a radio science package, plasma and charged particle sensors, and a dust counting experiment. These instruments enabled the first detailed exploration of a new class of outer solar system objects, the dwarf planets, which have exotic volatiles on their surfaces, escaping atmospheres, and satellite systems. NH also provided the first dust density measurements beyond 18~AU and cratering records that document both the ancient and present-day collisional environment in the outer solar system down to sizes of tens of meters. NH obtained unprecedented data on Pluto's small satellites (Styx, Nix, Kerberos, and Hydra), adding significantly to the scientific bounty returned from the NH mission. The NH spacecraft will be targeted toward the flyby of a small (~30 km) Kuiper Belt Object in late-2015, enabling the study of an object in a completely different dynamical class (cold classical) than Pluto, if NASA approves an Extended Mission phase.

Speaker: Ali Oguz Er, Applied Physics Institute, Western Kentucky University

Abstract: Various uses of lasers will be presented. A review of the nucleation and growth studies by Pulsed Laser Deposition (PLD) using in-situ reflection high energy electron diffraction (RHEED), atomic force microscopy (AFM), and scanning tunneling microscopy (STM) will be given.

Nanoscale heat transport across the Cu/Ag(111) interface and the transient structural disorder in Ag(111) crystal after excitation of the 18 nm copper with femtosecond pulses was studied by means of time resolved X-ray diffraction. The lattice disorder after UV irradiation is detected by changes in peak shift and broadening of the XRD rocking curve. We have observed blast force and pressure wave propagation.

The photo-inactivation rate of bacteria by methylene blue, MB, was found to be significantly lower in plasma than in water, saline, and PBS solutions. The spectroscopic data and ultrafast time resolved transient spectra and kinetics presented, show that methylene blue under continuous wave red light (~660 nm) photo-bleaches faster and to a larger degree in plasma and the MB excited singlet and triplet state populations in plasma are much lower in plasma than in water and PBS solutions.

Lastly, ongoing quantum control experiments by using femtosecond lasers in nonlinear media at Princeton University will be presented.

Speaker: Zbigniew Was, Institute of Nuclear Physics, Cracow, Poland

Abstract: One of the necessary step in confronting theory and experiment for accelerator experiments, is construction of the Monte Carlo programs simulating processes to be measured, using distributions calculated from theory. Agreement confirms theory, discrepancy point to New Physics phenomena or insufficent sophisticaltion of theoretical calculations. With the help of Monte Carlo simulations all theoretical and experimental effects can be simultaneously taken into account. In the present talk we will concentrate on tau lepton Monte Carlo generatiors; their use and decisive turning points in their development. Tauola, Photos and TaSpinner from part of the Monte Carlo spanned over more than 30 years now.