Digital Commons Network^™

Magnetic Measurements On Superconductors And Heavy Fermions., Donavan Weslee Hall

LSU Historical Dissertations and Theses

Magnetization and de Haas - van Alphen (dHvA) measurements have been made on the high temperature superconductor Ba$\sb{0.6}$K$\sb{0.4}$BiO$\sb3$ and the heavy fermion CeB$\sb6$. First ever observations of the dHvA effect in Ba$\sb{0.6}$K$\sb{0.4}$BiO$\sb3$ are reported. Two dHvA spectrometers (pulsed field and field modulation) were used to measure two samples. Four frequencies are found in the field modulation data with the 11.6 kT orbit in good agreement with band structure calculations. The three lowest frequencies were measured with the pulsed field spectrometer. All dHvA measurements were made in the superconducting mixed state. These measurements indicate that Ba$\sb{0.6}$K$\sb{0.4}$BiO$\sb3$ has a Fermi surface. Magnetization …

Electron Scattering Studies In The Framework Of The Symplectic Shell Model., Jutta Escher

LSU Historical Dissertations and Theses

Electron scattering offers numerous advantages for studying nuclear structure: the weakness of the electromagnetic interaction, the precise knowledge of the reaction mechanism, the ability to vary independently the transferred momentum and energy, as well as the excellent spatial resolution that can be obtained with the point-like probing particles, have made this approach a valuable tool in nuclear physics. Scattering experiments provide crucial tests for the applicability and limitations of modern nuclear models and further our understanding of the nucleon-nucleon interaction and its modifications in nuclear matter. A microscopic theory for deformed nuclei, which takes proper account of the Exclusion Principle …

Dynamical Effects Of Partial Orderings In Physical Systems, Adam S. Landsberg, Eric J. Friedman

WM Keck Science Faculty Papers

We demonstrate that many physical systems possess an often overlooked property known as a partial-ordering structure. The detection and analysis of this special geometric property can be crucial for understanding a system's dynamical behavior. We review here the fundamental dynamical features common to all such systems, and describe how the partial ordering imposes interesting restrictions on their possible behavior. We show, for instance, that though such systems are capable of displaying highly complex and even chaotic behaviors, most of their experimentally observable behaviors will be simple. Partial orderings are illustrated with examples drawn from many branches of physics, including solid …

Dynamics Of Conversion Of Conduction Electrons Into A Collective Charge-Density-Wave Current, Alexander S. Kovalev, Yuriy V. Pershin Dr, Alexander S. Rozhavsky

Faculty Publications

The exactly solvable model which describes the dynamics of transformation of conduction electrons into nonlinear charge-carrying excitations of charge-density waves in quasi-one-dimensional Peierls-Frohlich conductors is formulated and studied by the inverse scattering transformation method. The pair of self-trapped conduction electrons transform into a charged 2π kink localized in a single conducting chain and surrounded by dipoles in neighboring chains.

Smith On Krauss, 'The Physics Of Star Trek', Anne Collins Smith

Faculty Publications

Review of Lawrence M. Krauss.The Physics of Star Trek. New York: Basic Books, 1995. xvi + 188 pp. $20.00(cloth), ISBN 978-0-465-00559-8.

Reviewed by Anne Collins Smith (Austin Community College) Published on H-PCAACA (May, 1996)

Modeling Of The Polar Ionosphere In The Inertial Corotating Frame, Sergei Arkadevich Maurits

Theses (Unassigned)

The ionospheric model presented in this thesis is developed from first principles. It is a three-dimensional and time-dependent model that covers the region poleward from 50 degrees of geographic latitude and extends to the height range of 80-500 km. In this model, equations of continuity, motion, and energy balance are self-consistently solved for the densities of 7 ion species $\lbrack O\sp+(\sp4S,\ \sp2D,\ \sp2P),\ NO\sp+,\ O\sb2\sp+,\ N\sb2\sp+,\ N\sp+\rbrack$ and electrons. The model accounts for 40 photochemical processes, the neutral wind drag with its shear, electromagnetic E $\times$ B-drift, and field-aligned ambipolar diffusion. The background thermospheric parameters here are derived from the …

Oscillatory Doubly Diffusive Convection In A Finite Container, Adam S. Landsberg, Edgar Knobloch

WM Keck Science Faculty Papers

Oscillatory doubly diffusive convection in a large aspect ratio Hele-Shaw cell is considered. The partial differential equations are reduced via center-unstable manifold reduction to the normal form equations describing the interaction of even and odd parity standing waves near onset. These equations take the form of the equations for a Hopf bifurcation with approximate D4 symmetry, verifying the conclusions of the preceding paper [A.S. Landsberg and E. Knobloch, Phys. Rev. E 53, 3579 (1996)]. In particular, the amplitude equations differ in the limit of large aspect ratios from the usual Ginzburg-Landau description in having additional nonlinear terms with O(1) coefficients. …

Oscillatory Bifurcation With Broken Translation Symmetry, Adam S. Landsberg, Edgar Knobloch

WM Keck Science Faculty Papers

The effect of distant endwalls on the bifurcation to traveling waves is considered. Previous approaches have treated the problem by assuming that it is a weak perturbation of the translation invariant problem. When the problem is formulated instead in a finite box of length L and the limit L--> [infinity] is taken, one obtains amplitude equations that differ from the usual Ginzburg-Landau description by the presence of an additional nonlinear term. This formulation leads to a description in terms of the amplitudes of the primary box modes, which are odd and even parity standing waves. For large L, the equations …

Mechanisms And The Nature Of Causation, Stuart Glennan

Scholarship and Professional Work - LAS

In this paper I offer an analysis of causation based upon a theory of mechanisms – complex systems whose "internal" parts interact to produce a system's "external" behavior. I argue that all but the fundamental laws of physics can be explained by reference to mechanisms. Mechanisms provide an epistemologically unproblematic way to explain the necessity which is often taken to distinguish laws from other generalizations. This account of necessity leads to a theory of causation according to which events are causally related when there is a mechanism that connects them. I present reasons why the lack of an account of …

Cross-Tail Current Carriers In A Two-Dimensional Equilibrium Magnetotail Model, Douglas Johnston Larson

Doctoral Dissertations

The purpose of this study is to gain physical insight into how charged particles, that violate the guiding center approximations, contribute to cross-tail current in a self-consistent plasma sheet. A technique to generate self-consistent two-dimensional (2D) current sheets is described. Groups of monoenergetic protons are followed in a model magnetic field. The sample current sheets are characterized by resonant quasiadiabatic and stochastic orbits. Several ion and electron groups are combined to produce a plasma sheet in which the charged particles carry the currents needed to generate the magnetic field in which the orbits are traced. An electric field also is …

Deep Inelastic Scattering Of Polarized Electrons By Polarized ³He And The Study Of The Neutron Spin Structure, P. L. Anthony, R. G. Arnold, H. R. Band, H. Borel, P. E. Bosted, V. Breton, G. D. Cates, T. E. Chupp, F. S. Dietrich, J. Dunne, R. Erbacher, J. Felbauum, H. Fonvielle, R. Gearhart, R. Holmes, E. W. Hughes, J. R. Johnson, D. Kawall, C. Keppel, S. E. Kuhn, R. M. Lombard-Nelsen, J. Marroncle, T. Maruyama, W. Meyer, Z.- E. Meziani, H. Middleton, J. Morgenstern, N. R. Newbury, G. G. Petratos, R Pitthan, R. Prepost, Y. Robin, S. E. Rock, S. H. Rokni, G. Shapiro, T. Smith, P. A. Souder, M. Spengos, F. Staley, L. M. Stuart, Z. M. Szlata, Y. Terrien, A. K. Thompson, J. L. White, M. Woods, J. Xu, C. C. Young, G. Zaplac, E142 Collaboration

Physics Faculty Publications

The neutron longitudinal and transverse asymmetries A₁ⁿ and A₂ⁿ have been extracted from deep inelastic scattering of polarized electrons by a polarized ³He target at incident energies of 19.42, 22.66, and 25.51 GeV. The measurement allows for the determination of the neutron spin structure functions g₁ⁿ (x,Q²) and g₂ⁿ(x,Q²) over the range 0.032 of 2 (GeV/c)². The data are used for the evaluation of the Ellis-Jaffe and Bjorken sum rules. The neutron spin structure function g₁ⁿ(x,Q²) is small and …

Inclusive Electron Scattering From Nuclei At X≃1, J. Arrington, P. Anthony, R. G. Arnold, E. J. Beise, J. E. Belz, P. E. Bosted, H.- J. Bulten, M. S. Chapman, K. P. Coulter, F. Dietrich, R. Ent, M. Epstein, B. W. Filippone, H. Gao, R. A. Gearhart, D. F. Geesaman, J.- O. Hansen, R. J. Holt, H. E. Jackson, C. E. Jones, C. E. Keppel, E. R. Kinney, S. Kuhn, K. Lee, W. Lorenzon, A. Lung, N.C.R. Malkins, D. J. Margaziotis, R. D. Mckeown, R. G. Milner, B. Mueller, J. Napolitano, J. Nelson, T.G. O'Neill, V. Papavassiliou, G. G. Petratos, D. H. Potterveld, S. E. Rock, M. Spengos, Z. M. Szalata, L. H. Tao, K. Van Bibber, J.F.J. Van Den Brand, J. L. White, D. Winter, B. Zeidman

Physics Faculty Publications

The inclusive A(e,e') cross section for x≃1 was measured on ²H, C, Fe, and Au for momentum transfers Q² from 1 to 6.8 (GeV/c)². The scaling behavior of the data was examined in the region of transition from y scaling to x scaling. Throughout this transitional region, the data exhibit ξ scaling, reminiscent of the Bloom-Gilman duality seen in free nucleon scattering.

Basic Astronomy Labs, Terry L. Smith, Michael D. Reynolds, Jay S. Huebner

Physics Faculty Research and Scholarship

Providing the tools and know-how to apply the principles of astronomy first-hand, these 43 laboratory exercises each contain an introduction that clearly shows budding astronomers why the particular topic of that lab is of interest and relevant to astronomy. About one-third of the exercises are devoted solely to observation, and no mathematics is required beyond simple high school algebra and trigonometry.Organizes exercises into six major topics—sky, optics and spectroscopy, celestial mechanics, solar system, stellar properties, and exploration and other topics—providing clear outlines of what is involved in the exercise, its purpose, and what procedures and apparatus are to be used. …

Amorphization And Fracture In Silicon Selenium(2) Nanowires: Molecular-Dynamics Simulations On Parallel Computer Architectures., Wei Li

LSU Historical Dissertations and Theses

The primary goal of this dissertation is to investigate the structural and mechanical properties and dynamical fracture in SiSe$\sb2$ nanowires using the molecular-dynamics (MD) simulation technique. The present work is the first study of SiSe$\sb2$ nanowires. Large-scale simulations reported in this thesis are carried out with parallel multiresolution schemes for the long-range Coulomb and the three-body covalent potentials. The multiresolution scheme reduces the computational complexity from O(N$\sp2$) to O(N). Using an effective interatomic potential containing both 2- and 3-body interactions, MD simulations are performed for SiSe$\sb2$ nanowires composed of finite (1-64) number of chains. Under small uniaxial strain, the nanowires …

Effect Of Disorder On Synchronization In Prototype 2-Dimensional Josephson Arrays, Adam S. Landsberg, Yuri Braiman, Kurt Wiesenfeld

WM Keck Science Faculty Papers

We study the effects of quenched disorder on the dynamics of two-dimensional arrays of overdamped Josephson junctions. Disorder in both the junction critical currents and resistances is considered. Analytical results for small arrays are used to identify a physical mechanism which promotes frequency locking across each row of the array, and to show that no such locking mechanism exists between rows. The intrarow locking mechanism is surprisingly strong, so that a row can tolerate large amounts of disorder before frequency locking is destroyed.

Disorder And Synchronization In A Josephson Junction Plaquette, Adam S. Landsberg, Yuri Braiman, Kurt Wiesenfeld

WM Keck Science Faculty Papers

We describe the effects of disorder on the coherence properties of a 2 x 2 array of Josephson junctions (a "plaquette"). The disorder is introduced through variations in the junction characteristics. We show that the array will remain one-to-one frequency locked despite large amounts of the disorder, and determine analytically the maximum disorder that can be tolerated before a transition to a desynchronized state occurs. Connections with larger N x M arrays are also drawn.

Oscillons: Resonant Configurations During Bubble Collapse, E J. Copeland, M Gleiser, H R. Müller

Dartmouth Scholarship

Oscillons are localized, non-singular, time-dependent, spherically-symmetric solutions of nonlinear scalar field theories which, although unstable, are extremely long-lived. We show that they naturally appear during the collapse of subcritical bubbles in models with symmetric and asymmetric double-well potentials. By a combination of analytical and numerical work we explain several of their properties, including the conditions for their existence, their longevity, and their final demise. We discuss several contexts in which we expect oscillons to be relevant. In particular, their nucleation during cosmological phase transitions may have wide-rangingconsequences.

Radiation Transport In The Atmosphere - Sea Ice - Ocean System, Zhonghai Jin

Physics

A comprehensive radiative transfer model for the coupled atmosphere-sea ice-ocean system has been developed. The theoretical work required for constructing such a coupled model is described first. This work extends the discrete ordinate method, which has been proven to be effective in studies of radiative transfer in the atmosphere, to solve the radiative transfer problem pertaining to a system consisting of two strata with different indices of refraction, such as the atmosphere-ocean system and the atmosphere-sea ice-ocean system. The relevant changes (as compared to the standard problem with constant index of refraction throughout the medium) in formulation and solution of …

Justifying A Search For A Unifying Theory Of Unconstitutional Conditions, Roberto L. Corrada

Sturm College of Law: Faculty Scholarship

This essay explores why many scholars, including Frederick Schauer and Larry Alexander, feel that an attempt at unification of the doctrine of unconstitutional conditions is unworthy of scholarly attention. Although the subject of this particular essay is less ambitious than the many attempts that have been made to unify the doctrine of unconstitutional conditions, and indeed proposes no unifying theory itself, it nevertheless examines why attempts to explain the doctrine in a unified way might be valid even if no unification is ultimately possible. It also attempts to persuade that a unifying theory of the doctrine may be attainable, although …

Theory Of Spin Waves In Heisenberg Ferromagnetic And Antiferromagnetic Thin Films With Nonuniaxial Single-Ion Anisotropy, Paula R. Heron

Digitized Theses

This thesis describes the microscopic, quantum mechanical theory of exchange-dominated spin waves in Heisenberg ferromagnetic and antiferromagnetic thin films including the effects of nonuniaxial single-ion anisotropy. The results constitute a generalization of previous theoretical studies on spin waves in thin films with uniaxial anisotropy and in semi-infinite ferromagnets with nonuniaxial anisotropy.;A spin Hamiltonian containing nearest-neighbour exchange terms, Zeeman terms, and single-ion anisotropy terms is used. The films may be asymmetric with respect to surface exchange and anisotropy parameters which are also assured to be perturbed from the bulk values. The results apply both to cases in which the nonuniaxial anisotropy …

A-Dependence Of Nuclear Transparency In Quasielastic A (E, E'P) At High Q², T. G. O'Neill, W. Lorenzon, P. Anthony, R. G. Arnold, J. Arrington, E. J. Beise, J. E. Belz, P. E. Bosted, H.- J. Bulten, M. S. Chapman, K. P. Coulter, F. Dietrich, R. Ent, M. Epstein, B. W. Filippone, H. Gao, R. A. Gearhart, D. F. Geesaman, J.- O. Hansen, R. J. Holt, H. E. Jackson, C. E. Jones, C. E. Keppel, E. R. Kinney, S. Kuhn, K. Lee, A. Lung, N.C.R. Makins, D.J. Margaziotis, R. D. Mckeown, R. G. Milner, B. Mueller, J. Napolitano, J. Nelson, V. Papavassiliou, G. G. Petratos, D. H. Potterveld, S. E. Rock, M. Spengos, Z. M. Szalata, L. H. Tao, K. Van Bibber, J.F.J. Van Den Brand, J. L. White, B. Zeidman

Physics Faculty Publications

The A-dependence of the quasielastic A(e, ef'p) reaction has been studied at SLAC with ²H, C, Fe, and Au nuclei at momentum transfers Q² = 1, 3, 5, and 6.8 (GeV/c)². We extract the nuclear transparency T(A, Q²), a measure of the average probability that the struck proton escapes from the nucleus A without interaction. Several calculations predict a significant increase in T with momentum transfer, a phenomenon known as Color Transparency. Within the measurement uncertainty, no increase is seen for any of the nuclei studied.

Two-Body Photodisintegration Of The Deuteron Up To 2.8 Gev, J. E. Belz, D. H. Potterveld, S. E. Kuhn, J.F. J. Van Den Brand, J. L. White, B. Zeidman, Et Al.

Physics Faculty Publications

Measurements were performed for the photodisintegration cross section of the deuteron for photon energies from 1.6 to 2.8 GeV and center-of-mass angles from 37° to 90°. The measured energy dependence of the cross section at θ_c.m. = 90° is in agreement with the constituent counting rules.

Investigation In The Theory Of Stochastic Processes., Xiao Liang Li

LSU Historical Dissertations and Theses

In Chapter I of this dissertation, we present a pedagogical introduction to the basic concepts of stochastic theory and review the progress made as well as the outstanding unsolved problems in the field. For the rest of this dissertation, we use a generalized quantum Langevin equation (GLE) approach to investigate various properties of quantum dissipative systems. In Chapter II, calculations for the displacement and random force correlation functions for Brownian motion are generalized to the case of an arbitrary heat bath for a damped harmonic quantum oscillator. The mean square displacement of such an oscillator is then evaluated for both …

Phase Space Structures In Chaotic Quantum Dynamics., Barbara Smetana Helmkamp

LSU Historical Dissertations and Theses

I compare the quantum and classical dynamics of a particle moving in a cosine potential while subject to a time-dependent force. I concentrate here on the behavior of an initially well-localized wave packet at times before the classically chaotic motion is fully developed. I find that the quantum and classical dynamics are indistinguishable well beyond the Ehrenfest time where the wave packet delocalizes. The quantum and classical descriptions first differ precisely when the classical probability density is folded in the vicinity of a hyperbolic fixed point. At this point, the wave function acquires a nodal structure which I show to …

Electron Stimulated Desorption Of Alkali Halides, Islamshah Amlani

Mahurin Honors College Capstone Experience/Thesis Projects

No abstract provided.

An Investigation Of The Dynamics Of The Mesopause: Fabry-Perot Observations Of Winds And Temperatures From Nightglow Emissions, James F. Conner

Physics

This work is a study of the behavior of tidal and planetary waves in the upper-middle atmosphere near the geographic south pole. This is accomplished with a characterization of the dynamic state of these motions. I used ground-based Fabry-Perot Spectrometer (FPS) measurements of the multiple-line, $P\sb1$(2)$\sb{c,d}$, nightglow emissions from the X$\sp2$II band of the neutral OH* molecule. I developed analytical techniques to determine a space and time distribution of spectral amplitudes and phases for the dynamic parameters of kinetic temperature and neutral wind in the OH* layer. Spectral analysis of the variations in this layer indicate the existence of two …

Nitrogen Oxides In The Arctic Stratosphere: Implications For Ozone Abundances, James Robert Slusser

Physics

In the high latitude winter stratosphere, NO$\sb2$ sequesters chlorine compounds which are extremely efficient at destroying ozone. During the nighttime, NO$\sb2$ reacts with ozone to form $\rm N\sb2 O\sb5$ which acts as a reservoir of NO$\sb2$. Under heavy aerosol loading, $\rm N\sb2O\sb5$ may react with water on aerosol surfaces to form HNO$\sb3$, a reservoir more resistant to photolysis. This heterogeneous reaction results in reduced NO$\sb2$ concentration when the sun returns at the end of the winter. A spectrograph system has been developed to measure scattered zenith skylight and thereby determine stratospheric NO$\sb2$ slant column abundance. Conversion of the measured slant …

Absence Of Size Dependence Of The Kondo Resistivity, V. Chandrasekhar, P. Santhanam, N. A. Penebre, Richard A. Webb, H. Vloeberghs, C. Van Haesendonck, Y. Bruynseraede

Faculty Publications

We have measured the low temperature resistivity of AuFe wires in the dilute magnetic impurity limit as a function of wire width, temperature, and magnetic field. When the width dependence of the electron-electron interaction contribution to the resistivity is taken into account, the temperature dependence of the remaining Kondo contribution to the resistivity of all samples with the same impurity concentration is identical. Similar behavior is observed for the magnetic field dependent resistivity. Thus, the Kondo contribution to the resistivity is independent of width down to 38 nm, much smaller than the Kondo length ξ_K=ħv_F/k_{B …}

Discrete Singularity Method And Its Application To Incompressible Flows., S K. Venkatesan Dr.

Doctoral Theses

The smooth flow of a fluid has sprung many surprises. A flow which at an instant of time is quite regular and orderly could produce on the slightest of disturbance a complex bewildering varieties of flows, broadly termed as turbulence. Direct numerical simulation of the Navier-Stokes equations have shown that it is quite possible that these turbulent flows are solutions of the Navier-Stokes equations. In fact it is by now well recognized that many non-linear systems produce chaos quite similar to turbulence. However the large number of scales and their complex interactions involved make turbulence difficult to understand. Direct numerical …

Wooster Magazine: Winter 1994, Peter Havholm

Wooster Magazine: 1991-2000

This edition of the Wooster Magazine was published in the winter of 1993. This issue focuses on Black Studies at the College and the experiences of Black Alumni. The first article in the features section complies responses from Black alumni about their experiences at the College of Wooster. The second article is a "sketch" of what Black Studies at the College look like. Other topics covered include swimming and physics. Alumni News and Class Notes are featured at the end of the issue.