Master of Science

ThesisThe work of this thesis was carried on in the Metallurgical Research laboratories of the University of Utah,; in connection with the U. S. Bureau of Mines. The work was under the direct supervision of O. C. Ralstonn, who; is Metallurgist at the Salt Lake Station

A site-controlled quantum dot system offering both high uniformity and spectral purity

In this paper we report on the optical properties of site controlled InGaAs dots with GaAs barriers grown in pyramidal recesses by metalorganic vapour phase epitaxy. The inhomogeneous broadening of excitonic emission from an ensemble of quantum dots is found to be unusually narrow, with a standard deviation of 1.19 meV, and spectral purity of emission lines from individual dots is found to be very high (18-30 ueV), in contrast with other site-controlled systems.Comment: 12 pages, 3 figure

Development of the technology for the fabrication of reliable laminar from control panels

Materials were assessed and fabrication techniques were developed for use in the manufacture of wing surface materials compatible with the application of both aluminum alloys and nonmetallic composites. The concepts investigated included perforations and slots in the metallic test panels and microporosity and perforations in the composite test panels. Perforations were produced in the metallic test panels by the electron beam process and slots were developed by controlled gaps between the metal sheets. Microporosity was produced in the composite test panels by the resin bleed process, and perforations were produced by the fugitive fiber technique. Each of these concepts was fabricated into test panels, and air flow tests were conducted on the panels

Locating Star-Forming Regions in Quasar Host Galaxies

We present a study of the morphology and intensity of star formation in the host galaxies of eight Palomar-Green quasars using observations with the Hubble Space Telescope. Our observations are motivated by recent evidence for a close relationship between black hole growth and the stellar mass evolution in its host galaxy. We use narrow-band [O II] $\lambda$3727, H$\beta$, [O III] $\lambda$5007 and Pa$\alpha$ images, taken with the WFPC2 and NICMOS instruments, to map the morphology of line-emitting regions, and, after extinction corrections, diagnose the excitation mechanism and infer star-formation rates. Significant challenges in this type of work are the separation of the quasar light from the stellar continuum and the quasar-excited gas from the star-forming regions. To this end, we present a novel technique for image decomposition and subtraction of quasar light. Our primary result is the detection of extended line-emitting regions with sizes ranging from 0.5 to 5 kpc and distributed symmetrically around the nucleus, powered primarily by star formation. We determine star-formation rates of order a few tens of M$_\odot$/yr. The host galaxies of our target quasars have stellar masses of order $10^{11}$ M$_\odot$ and specific star formation rates on a par with those of M82 and luminous infrared galaxies. As such they fall at the upper envelope or just above the star-formation mass sequence in the specific star formation vs stellar mass diagram. We see a clear trend of increasing star formation rate with quasar luminosity, reinforcing the link between the growth of the stellar mass of the host and the black hole mass found by other authors.Comment: Accepted for publication in M.N.R.A.

Degeneracy and Strong Fluctuation-Induced First-Order Phase Transition in the Dipolar Pyrochlore Antiferromagnet

We show that a continuous set of degenerate critical soft modes strongly enhances the first-order character of a fluctuation-induced first-order transition in the pyrochlore dipolar Heisenberg antiferromagnet. Such a degeneracy seems essential to explain the strong first-order transition recently observed in Gd(2)Sn(2)O(7). We present some evidence from Monte-Carlo simulations and a perturbative renormalization group expansion.Comment: 8 pages, 9 figures, new version to appear in PRB, added ref

Fast vectorized algorithm for the Monte Carlo Simulation of the Random Field Ising Model

An algoritm for the simulation of the 3--dimensional random field Ising model with a binary distribution of the random fields is presented. It uses multi-spin coding and simulates 64 physically different systems simultaneously. On one processor of a Cray YMP it reaches a speed of 184 Million spin updates per second. For smaller field strength we present a version of the algorithm that can perform 242 Million spin updates per second on the same machine.Comment: 13 pp., HLRZ 53/9

Sound Propagation in Nematic Fermi Liquid

We study the longitudinal sound propagation in the electronic nematic Fermi liquid where the Fermi surface is distorted due to the spontaneously broken rotational symmetry. The behavior of the sound wave in the nematic ordered state is dramatically different from that in the isotropic Fermi liquid. The collective modes associated with the fluctuations of the Fermi surface distortion in the nematic Fermi liquid leads to the strong and anisotropic damping of the sound wave. The relevance of the nematic Fermi liquid in doped Mott insulator is discussed.Comment: 4 pages, no figur

Thermodynamic properties of spin-1/2 transverse XY chain with Dzyaloshinskii-Moriya interaction: Exact solution for correlated Lorentzian disorder

We extend the consideration of the spin-1/2 transverse XY chain with correlated Lorentzian disorder (Phys. Rev. B {\bf 55,} 14298 (1997)) for the case of additional Dzyaloshinskii-Moriya interspin interaction. It is shown how the averaged density of states can be calculated exactly. Results are presented for the density of states and the transverse magnetization.Comment: 2 figure

Rotational resonance of magnetoinductive waves: Basic concept and application to nuclear magnetic resonance

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