"Modeling Eclipsing Binary Stars from Light Curves"

Dr. Dan Bruton
Department of Physics and Astronomy
Stephen F. Austin State University
Nacogdoches, Texas

Tuesday, April 20, 2004
3:30 p.m., Room 104, Physics Bldg.

Refreshments
3:00 p.m., Room 113
Physics Commons Room (Lounge)

Abstract:

Eclipsing binary stars are just one several types of variable stars. These stars appear as a single point of light to an observer, but based on its brightness variation and spectroscopic observations we can say for certain that the single point of light is actually two stars in close orbit around one another. The variations in light intensity from eclipsing binary stars is caused by one star passing in front of the other relative to an observer. A brightness versus time plot for a variable star is know as light curve. From these plots we can determine the relative masses and radii of the two stars as well as a few of the orbital parameters. http://www.physics.sfasu.edu/astro/binstar.html

Spring 2004 Colloquia

January 27

Dr. Jose Perez, Department of Physics, University of North Texas, Denton, Texas

"Growth and Characterization of Semiconducting Silicide Quantum Dots"

Possible semiconducting silicide quantum dot systems such as iron disilicide, osmium-iron disilicide ternary compounds and ruthenium disilicide and their potential applications will be discussed. Experimental results on self assembled iron disilicide quantum dots on Si (111) surfaces will be presented including atomic resolution scanning tunneling microscopy and atomic force micorscopy images.

February 3

Dr. Yuriy A. Kosevich, Instituto de Investigacion en Comunicacion Optica, Universidad Autonoma de San Luis Potosi, San Luis Potosi, Mexico

"Magneto-Bloch oscillations, coherent Hall effect and nonlinear magnetotransport in semiconductor superlattices"

In this presentation, we discuss transient coherent magneto-Bloch oscillations (MBO's) of an electronic wave packet in crossed electric and magnetic fields and also temporal transition to nonlinear magneto-transport in a biased semiconductor superlattice. It is shown that the full-miniband MBO's of an electronic wave packet in parallel magnetic field give rise to an anomalous Hall velocity which is proportional to the magnetic field and the reciprocal of the electric field, and whose magnitude and sign depend on the excitation conditions (Coherent Hall Effect). The electric-field-induced transition from the ordinary to anomalous Hall drift velocity causes a strong parallel-magnetic-field dependence of the peak carrier velocity in a superlattice in strong crossed fields.

February 10

Professor Suresh C. Sharma, Department of Physics, University of Texas at Arlington, Arlington, Texas

“Optical and Electronic Properties of Molecular C₆₀, Single-walled Carbon Nanotubes, and Liquid-crystal Droplets in Polymers”

I will present an over view of our current research programs on the; 1) properties of C60-based fullerenes under high pressures, 2) possibility of fluid insertion into Single-Walled Carbon Nanotubes (SWCNT’s), 3) growth of fullerene thin films and characterization of their electronic properties at low temperatures, and 4) role of interfacial charges in the optical properties of polymer-dispersed liquid crystal devices (PDLC’s). Research Supported by: U. S. Department of Energy, Welch Foundation, and Texas Advanced Technology Program.

February 17

Dr. David L. Allara, Department of Chemistry and Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania

“Building Molecule-Based Electronic Devices”

Rapid progress has been made in the fabrication and testing of molecule-based electronic devices.  Scientific challenges deal with metal-molecule interfaces, optimum methods for surface self-assembly, fundamental mechanisms of charge transport, and device activity such as switching.  We outline these issues and then discuss our own approach using surface science.  We present examples in the areas of metal-molecule interactions, mechanisms of surface assembly, and single molecule device measurements.  The talk will also highlight current connections between electrical transport and molecular structures.

February 24

Dr. John Prince, Department of Physics, University of North Texas, Denton, Texas

“An Overview of Contemporary Medical Physics”

Medical Physics has evolved over the past several decades into both a professional and scientific discipline.  Entrepreneurs have also created a business niche in the U.S. sector.  This presentation will provide a personal view of the current practice of medical physics in the United States from a clinical perspective.

Professor Anzhong Wang, Center for Astrophysics, Space Physics, & Engineering Research, Department of Physics, Baylor University, Waco, Texas

“Hierarchy Problem and ‘Brane’-world Scenarios”

I shall give a general review of M-theory (Mem-brane theory/superstrings) on recent developments in “brane-world” scenarios that were designed to solve the long-standing hierarchy problem in particle and gravitational physics. I shall pay particular attention to some recent models proposed since 1998, including some new limits placed on them obtained from (1) particle accelerators, (2) high-energy astrophysics, and (3) experimental tests of deviations from Newton's law of gravity. Finally, I shall briefly mention some of my work in this area.

Dr. Jeffrey Bennett, Astrophysicist and Science Writer

“Strategies for Teaching Science”

No matter who you are teaching, a few key strategies are always useful. After an introduction on teaching philosophy, I will discuss five key strategies for teaching science, with examples drawn primarily from astronomy and physics:

(1)    Provide a Contextual Framework: It is much easier to learn new facts or concepts if they can be "binned" into a pre-existing mental framework that gives a broad context for the detailed study to be undertaken.

(2)    Create Conditions for Conceptual Change: Many people hold misconceptions about scientific ideas. Therefore we cannot teach them the correct ideas unless we first help them unlearn their prior misconceptions.

(3)    Make the Material Relevant: It's human nature to be more interested in subjects that seem relevant to our lives. Therefore we must show students the many connections between science and their personal concerns.

(4)    Limit Use of Jargon: The number of new terms in many introductory science books is larger than the number of words taught in many first courses in foreign language, which is a clear recipe for failure. We must find ways to replace jargon with plain language.

(5)    Challenge Your Students: Don't dumb your teaching down; by and large, students will rise to meet your expectations, as long as you follow the other strategies and practice good teaching.

Bio: Dr. Jeffrey Bennett is an astrophysicist (Ph.D, 1987 University of Colorado) who specializes in math and science education. He has taught at every level from elementary school through college, and is the author of leading college-level textbooks in astronomy, mathematics, statistics, and the new science of astrobiology. He served two years as a Visiting Senior Scientist at NASA headquarters, where he developed education programs for the Hubble Space Telescope and other astrophysics missions. He proposed the idea for and helped develop the Voyage Scale Model Solar System, a permanent, outdoor exhibit on the National Mall in Washington, DC. Learn more about Dr. Bennett at http://www.jeffreybennett.com

Professor Sam Matteson, Department of Physics, University of North Texas, Denton, Texas

"The Sun, The Moon, The Cross: Dating the Crucifixion"

The passion of Jesus of Nazareth is one of the pivotal events of the Christian faith and, indeed, of western civilization. This lecture brings together knowledge gleaned from the historical records, the Christian canon, calendric practices of the first century, celestial mechanics and archaeoastronomy to investigate the possible dates of the crucifixion of Jesus, called the Christ.  The death of Jesus is associated with the springtime festival of Passover that occurs on 14 Nisan in the Judaic luni-solar calendar.  Since the calendar of the first century was set by direct observation we have the opportunity to exploit celestial mechanics to determine the beginnings (Hodesh) of the ancient Hebrew months during the period 26 CE  (AD) to 36 CE (AD), the period of time that Pontius Pilate was governor of Judea. With this information we may proceed to ascertain for which years the Passover began on a Thursday or Friday and identify the most likely date of the events of the final chapters of the gospels. 

Dr. Zhibing Hu, Department of Physics, University of North Texas, Denton, Texas

"Phase Behavior of Colloids in Water with a Thermally Tunable Particle Size"

Colloidal particles suspended in a liquid behave like large idealized atoms that exhibit liquid, glass, and crystal phases similar to those observed in atomic systems. However, what should the phase behavior be like if the atom's size could expand or shrink? In this talk, the phase behavior of thermally responsive microgel colloids will be discussed. The colloidal particles in this study are made of poly-N-isopropylacrylamide and drastically change their sizes from 140 nm to 55 nm in the temperature span between room temperature and body temperature. It will be shown that the volume transition of these particles affects the inter-particle interaction potential and determines a novel phase diagram that has not been observed in atomic-sphere-like colloidal dispersions.

Professor R. F. O'Connell, Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana

“Dissipation (Friction) in Quantum Mechanics with Applications”

Car tires on a road, raindrops falling through the atmosphere and the Brownian motion of particles in a fluid are reviewed as examples of phenomenological friction theories.  Next, a microscopic theory is presented which leads to a generalized quantum Langevin theory that is shown to embrace a rich variety of phenomena. Applications of the theory include the solution of the problems of (1) runaway solutions in quantum electrodynamics, (2) atomic energy shifts due to blackbody radiation,  (3) entropy of an oscillator in a heat bath, and (4) decoherence problems in quantum theory.

Professor Wolfgang Schleich, Abteilung für Quantenphysik, Universität Ulm, Ulm, Germany

"Interference, Correlations and Entanglement in Higher Dimensions: Quantum Information"

Quantum mechanics has correlations between position and momentum that are stronger than in classical mechanics. These correlations depend crucially on the number of dimensions of space. They are impossible to visualize using wave functions, since complementarity only allows us to consider position or momentum wave functions. The Wigner function approach to quantum mechanics gives us a quantum mechanical description in phase space. Interference occurs in domains of phase space where the Wigner function is negative. We introduce a Wigner function that depends only on the magnitudes of the position and momentum vectors, and the angle between them.. This angle describes entanglement. We discuss the relevance of these considerations for quantum information.

April 16

Dr. Daniel K. Marble, Department of Mathematics, Physics, & Engineering, Tarleton State University, Stephenville, Texas

“Profiling Impurities Using Nuclear Reaction Analysis”

Impurities can dramatically alter the mechanical, chemical, and electrical properties of a material. Since ions can be trapped at defect sites, the study of diffusion and trapping mechanisms for light ions is a very active field of research. One ion beam technique capable of profiling impurities in materials is Nuclear Reaction Analysis (NRA).  This technique has found only limited acceptance by industry due to space and sensitivity limitations. The talk will present results from a collaborative research effort to develop a new compact, high sensitivity NRA detection system and to apply it to various problems. 

April 20

Fall 2003 Colloquia

Dr. Sam Matteson, Department of Physics, University of North Texas, Denton, Texas

"Power Pointers: Using Technology for Teaching"

"Effective use of technology requires an understanding of how people learn and how visual communication works. The lecture will review the effective use of Power Point graphics as it relates to learning. The lecture will reveal the principles, some applications and a tutorial for producing effective, stimulating and time efficient presentations." 

Sam Matteson is a professor of Physics and past Chair of the Department of Physics at UNT. He has developed several highly evaluated courses based on technology and effective visual explanation. He gladly shares the secrets of the craft with students and colleagues.

September 23

Dr. Roland Allen, Department of Physics, Texas A&M University, College Station, Texas

"Response of Matter to Ultrafast and Extremely Intense Laser Pulses"

It is now possible to create laser pulses with durations of only a few femtoseconds and intensities far above a terawatt. Such pulses are extremely useful for probing physical, chemical, and biological phenomena on short time scales. In addition, properly shaped ultrashort pulses may be useful for controlling chemical reactions and achieving controlled nuclear fusion. The prospects for still shorter pulses will also be discussed.

Professor Arkadii Krokhin, Department of Physics, University of North Texas, Denton, Texas

“Speed of Light and Sound in Photonic and Phononic Crystals”

New periodic heterostructures – photonic crystals – are expected to produce new media for information technology by replacing traditional electronic devices by integrated photonic circuits. In this talk I’ll consider fundamental optical properties of photonic crystals in the low-frequency region. The question of interest is: What is the speed of light in photonic crystals? Answering this question we can understand what are the similarities and distinctions between optics of natural crystals and artificial photonic crystals. Similar question arises for phononic crystal – periodic elastic composites. I will consider the problem of speed of sound in mixtures. I will explain why in water with a speed of sound 1% that of air the speed of sound drops by two orders of magnitude. 

Dr. Linda Reichl, Center for Statistical Mechanics and Complex Systems, University of Texas, Austin, Texas

“Photon Induced Chaotic Scattering and Phase Space Tunneling in Atomic Systems”

The dynamics of monochromatic electromagnetic fields interacting with atomic systems is governed by a conservation law that allows the creation of new stable electron-photon states. These states have been observed in recent cold atom optics experiments. The effect of this conservation law can also be observed in open systems where monochromatic fields can induce a chaotic dynamics which can support quasi-bound electronic states and delay ionization of electrons.  Signatures of chaos-induced quasi-bound states appear in scattering phase shifts and delay times.

Dr. Wolfgang Schleich, University of Ulm, Ulm, Germany

"What is a Photon?"

We present a brief history of the photon and summarize the canonical procedure to quantize the radiation field. The Wigner representation of quantum mechanics applied to a single photon state elucidates the nature of the photon. The Fresnel transform of the Wigner function will also be discussed from an operational point of view.

Dr. Bruce J. West, Senior Research Scientist, Mathematics Division, Army Research Office, Research Triangle Park, North Carolina

“Complexity Produces Strange Kinetics and Dynamics”

Complexity has historically been modeled in the physical sciences through the introduction of probability densities and phase space equations of evolution - the master equation. In the early 1970’s certain phenomena were discovered that could not be described by the traditional phase space equations or random walks and required new models, such as Levy distributions. These complex phenomena required the introduction of memory into random walk models for their description. Alternative models for the inclusion of memory were developed, such as fractional random walks and in the continuum limit fractional diffusion equations. A number of applications of these techniques to such phenomena as turbulence, nonlinear stress relaxation, and human gait are also discussed.

Texas Section APS/AAPT/SPS Meeting, Texas Tech University, Lubbock, Texas

Professor Arup Neogi, Department of Physics, University of North Texas, Denton, Texas

“Optical Properties of Semiconductor Nanostructures for Photonic Applications”

 The optical properties of semiconductor nanostructures, including quantum wells, quantum dots, and self-assembled organic-inorganic material systems, significant for designing optoelectronic and photonic applications will be discussed. We are studying the fundamental properties of these materials systems using various optical diagnostic techniques based on ultrafast lasers. The nano-photonic material research program and the existing experimental facilities being developed at the Department of Physics at UNT will be presented.

Dr. Mini Das, Physics Department,  Indian Institute of Technology, Delhi, India

“Fiber gratings: Properties and Applications”

Fiber gratings are emerging as a key element in the field of optical communication and optical fiber sensing.  Fiber gratings are essentially formed by inducing periodic refractive index change in the core of the optical fiber. This periodic perturbation leads to coupling of optical power between the fiber modes, resulting in interesting spectral properties that could be controlled by changing the grating properties. The talk would cover a brief introduction to fiber gratings and their mode coupling properties followed by classification of gratings. Some important applications of these in dispersion compensation and sensing would be discussed. Experimental results on the demonstration of the first fiber based polariser would be elaborated (Experiments conducted at the fiber optics division of Bell Laboratories, NJ, USA). Brief discussion on the recent research advances in this field including an inverse scattering technique that is used to design gratings with desired spectral response would conclude the talk.

Dr. Jacek Kowalski, Department of Physics, University of North Texas, Denton, Texas

“Real World Networks”

Real-world networks such as power grids, World-Wide Web, the Internet, biological and social networks exhibit interesting scaling properties that cannot be explained in the framework of "classical" random graph theory. Strong clustering is another feature of such real-life networks. Analysis of their robustness is a challenging problem of obvious importance. A review of several popular approaches to the description of such systems will be discussed and some open problems given.

Dr. Manfred A. Cuntz, Department of Physics, University of Texas at Arlington, Arlington, Texas

“Stars, Planets and Stellar Activity Enhancements”

I will summarize recent findings about extra-solar planets and their host stars.  More than 100 planets outside the Solar System have been identified.  Knowledge has also been attained concerning star-planet relationships.  An unexpected finding is that close-in giant (Jupiter-size) planets noticeably increase stellar activity.  Three different modes of interaction may be distinguished, which are gravitational (tidal) interaction, magnetic interaction, and rotational synchronization.  Magnetic interaction manifests itself in sporadic heating phenomena, akin to well-known flaring events between RS CVn binaries, but at much smaller scales.  Observational support for this picture has been obtained in four out of five 51 Peg-typ planet stars that allow constraints on exosolar planetary magnetic fields and dynamo activity.

Dr. Gerald B. Cleaver, Center for Astrophysics, Space Physics & Engineering Research, Department of Physics, Baylor University,
Waco, Texas

“Superstring/M-Theory Cosmology”

The enhancement of superstring theory to M-theory has profound implications for cosmology. I review the most significant aspects of the M-theory cosmological picture resulting from the combined effects of (1) M-theory’s (10+1)-dimensional spacetime (compared to string theory’s (9+1)-dimensional spacetime), (2) M-theory’s realization that strings have a width determined by the size of the additional spatial direction (transforming strings into membranes), and (3) the M-theory prediction of spatial surfaces called D-branes. The role of membranes and D-branes in the pre-Big Bang and inflationary eras are discussed. M-theory revisions of the original Brandenberger-Vafa string inflation model are briefly summarized. I also discuss the Randall-Sundrum model and its extensions, which offer a D-brane explanation for the apparent weakness of gravity in our 3+1 large dimensions.

Professor Arkady Krokhin, Instituto do Fisica, Universidad Autonoma de Puebla, Puebla, Mexico

"Regular and Chaotic Transport in Semiconductor Superlattices and  Photonic Crystals"

Professor Paolo Grigolini, Department of Physics, University of North Texas, Denton, Texas

"Aging Processes in Physical Systems"

Onsager's postulate states that the average regression of thermal fluctuation follows the macroscopic law of relaxation. This is one of the fundamental tenets of statistical mechanics together with linear response theory and the Wiener-Kintchine theorem. Two distinct procedures are proposed for the dynamic foundation of statistical mechanics: (1) the master equation and (2) the continuous time random walk. We examine under which conditions they are equivalent. We find that in the case of a two-state system they are equivalent only in the Poissonian case. We prove that the breakdown of this equivalence stems from the fact that non-Poissonian processes yield aging processes violating Onsager's postulate. In fact, this postulate is valid for “aged” systems, namely systems that "have been isolated for a length of time that is normally sufficient to secure thermodynamic equilibrium." New materials, like the so-called blinking quantum dots, are characterized by aging, thereby implying that a new theory must be developed for both emission and absorption processes.

Professor Donald Kobe, Department of Physics, University of North Texas, Denton, Texas

"Gauge Invariance in Classical and Quantum Mechanics"

A single charged particle in a time-dependent external, electromagnetic field is considered in both classical and quantum mechanics. The Hamiltonian and energy of the particle are obtained. The Hamiltonian is gauge dependent and the energy is gauge invariant, so in general they are not equal. The equation of motion is obtained from the Hamiltonian. The time rate of change of the energy is equal to the power supplied to the particle by the external electromagnetic field. In quantum mechanics, transitions between states are determined by matrix elements of the power operator.

February 11

Dr. Victor V. Kozlov, Abteilung fuer Quantenphysik, Universitaet Ulm, Germany

"Soliton Theory for Modern Quantum Technologies" 

Fundamental and applied aspects of nonlinear propagation of solitons and solitary waves in optical fibers are overviewed in context of their information capacity, with main emphasis on the transition from classical concepts towards quantum dynamics. Classical solitons are known as self-organizing themselves into stable spatially and temporally localized objects, and as such are considered as robust carriers of classical information. The talk will address the question of whether quantum solitons can serve equally well for carrying quantum information. The discussion will include: How to entangle two or more initially uncorrelated solitons, how to entangle (actually, intra-entangle) a soliton with itself, and how to design a quantum-optical network - quantum Internet.

Professor Sam Matteson, Department of Physics, University of North Texas, Denton, Texas

"Mirages, Loomings and the Wonder of Ahaz's Stairs"

A careful look at the details of the formation of refractive phenomena in the atmosphere provides a plausible explanation of a famous wonder from seventh century BC Jerusalem. During the reign of Hezekiah, one of the most archeologically well known of the pre-exilic Judean Kings, an event allegedly occurred that was a wonder: the shadow cast by the sun when backwards on a "sun dial." The speaker will marshall evidence from the physics of atmospheric phenomena, archeology and history to provide a plausible reconstruction of this remarkable event.

Professor Constantino Tsallis, Brazilian Center for Research in Physics, Rio de Janeiro, Brazil

"Boltzmann-Gibbs Statistical Mechanics: A First or a Last Step?"

Ubiquitous phenomena exist in natural and artificial systems for which Boltzmann-Gibbs statistical mechanics and standard thermodynamics are hardly applicable, or not at all. A large class of such situations, those which present a hierarchical or multifractal structure in phase space, maybe studied by using an entropy which generalizes the usual one. A brief review of the formalism, its dynamical foundation, and its most recent applications will be given.

March 25

Professor Jianzhong Wu, Dept. of Chemical and Environment Engineering, University of California, Riverside
Riverside, California

"Crystallization, Metastable Phase Transition and Percolation in Colloidal Dispersions"

April 1

Dr. Richard Stallcup, Research Physicist, Zyvex Corporation, Richardson, Texas

"Nano Scale Surface Modification by Scanning Probe Microscopy"

Zyvex is the world's first molecular nanotechnology company. Our mission is to be the leading worldwide supplier of tools, products, and services that enable adaptable, affordable, and molecularly precise manufacturing. Single molecule manipulation in ultra-high vacuum and nano scale molecular grafting in liquids by scanning probe microscopy will be presented. These two processes are examples of a long-term research effort by Zyvex to explore nano scale fabrication of electrical and mechanical systems. In addition, the short-term market driven efforts are research in MEMS (microelectromechanical systems), nanocomposite materials, and instrumentation development.

April 15

Jack G. Hehn, Director of Education, American Institute of Physics, College Park, Maryland

“Issues for Physics Departments: To Increase Majors and To Prepare Better Teachers”

The American Institute of Physics (AIP) in collaboration with its ten Member Societies undertakes a number of programs to strengthen physics departments and their programs.  AIP staff members visit University campuses and meet with members of the Society of Physics Students (SPS), groups of faculty and administrators, and local employers to learn more about current concerns.  I will talk about two specific AIP programs as examples. (1) The National Task Force on Undergraduate Physics has published a report “Strategic Programs for Innovation in Undergraduate Physics” giving examples of Physics Departments that have shown success in increasing physics majors and student participation. (2) The Physics Teacher Education Coalition is a program designed to increase the role of Physics Departments in the science preparation of future teachers in grades K-12.  An outcome of this program is to  form a coalition of colleges and universities to take a leadership role in preparing future teachers.