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Local Optical Properties, Electron Densities, And London Dispersion Energies Of Atomically Structured Grain Boundaries, Roger H. French Nov 2004

Local Optical Properties, Electron Densities, And London Dispersion Energies Of Atomically Structured Grain Boundaries, Roger H. French

Faculty Scholarship

Quantitative analysis of spatially resolved valence electron energy-loss spectra shows strong physical property contrasts for Σ5 and near Σ13 grain boundaries in Fe-doped SrTiO3, resulting in London dispersion interaction energies of 14 to 50mJ/m2 between the adjacent grains. The determination of local physical properties of grain boundary cores and the appreciable contribution of long-range London dispersion to interface energies provides new information on formation and control of interfaces in materials.

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The Structures Of C-C4F8 And C-C4F8¯ And The Adiabatic Electron Affinity Of C-C4F8, Gordon A. Gallup Nov 2004

The Structures Of C-C4F8 And C-C4F8¯ And The Adiabatic Electron Affinity Of C-C4F8, Gordon A. Gallup

Gordon Gallup Publications

Calculations at the 6311G(dps) level have been used to elucidate the structures of octafluorocyclobutane c-C4F8 and its negative ion c-C4F8¯. With no empirical adjustments, we obtain 0.640 eV for the adiabatic electron affi nity of c-C4F8. This may be compared with an experimental value of 0.63 ± 0.05 eV from the FALP method. c-C4F8 has unusual features in that there is an increase in symmetry, D2d to D4h, in going from the neutral molecule to the negative ion, and …

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Mechanism And Control Of High-Intensity-Laser-Driven Proton Acceleration, T. Lin, K. Flippo, M. Rever, Anatoly Maksimchuk, Donald P. Umstadter Nov 2004

Mechanism And Control Of High-Intensity-Laser-Driven Proton Acceleration, T. Lin, K. Flippo, M. Rever, Anatoly Maksimchuk, Donald P. Umstadter

Donald Umstadter Publications

We discuss the optimization and control of laser-driven proton beams. Specifically, we report on the dependence of high-intensity laser accelerated proton beams on the material properties of various thin-film targets. Evidence of star-like filaments and beam hollowing (predicted from the electrothermal instability theory) is observed on Radiochromic Film (RCF) and CR-39 nuclear track detectors. The proton beam spatial profile is found to depend on initial target conductivity and target thickness. For resistive target materials, these structured profiles are explained by the inhibition of current, due to the lack of a return current. The conductors, however, can support large propagating currents …

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The Nuclear Reddening Curve For Active Galactic Nuclei And The Shape Of The Infrared To X-Ray Spectral Energy Distribution, C. Martin Gaskell, René W. Goosmann, Robert R. J. Antonucci, David H. Whysong Nov 2004

The Nuclear Reddening Curve For Active Galactic Nuclei And The Shape Of The Infrared To X-Ray Spectral Energy Distribution, C. Martin Gaskell, René W. Goosmann, Robert R. J. Antonucci, David H. Whysong

Department of Physics and Astronomy: Faculty Publications

We present extinction curves derived from the broad emission lines and continua of samples of 72 radio-loud and 1018 radio-quiet active galactic nuclei (AGNs). The curves are significantly flatter in the UV than curves for the local interstellar medium. The reddening curves for the radio-quiet Large Bright Quasar Survey quasars are slightly steeper than those of the radio-loud quasars in the UV, probably because of additional reddening by dust farther out in the host galaxies of the former. The UV extinction curves for the radio-loud AGNs are very flat. This is explicable with slight modifications to standard Mathis-Rumpl-Nordsieck dust models: …

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Combination Of Cdf And D0 Results On The W Boson Mass And Width, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Nov 2004

Combination Of Cdf And D0 Results On The W Boson Mass And Width, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

The results based on 1992–95 data (Run 1) from the CDF and D0 experiments on the measurements of the W boson mass and width are presented, along with the combined results. We report a Tevatron collider average MW =80.456±0.059 GeV. We also report the Tevatron collider average of the directly measured W boson width ΓW=2.115±0.105 GeV. We describe a new joint analysis of the direct W mass and width measurements. Assuming the validity of the standard model, we combine the directly measured W boson width with the width extracted from the ratio of W and Z boson …

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Substructure Dependence Of Jet Cross Sections At Hera And Determination Of ΑS, S. Chekanov, M. Derrick, J. H. Loizides, S. Magill, S. Miglioranzi, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, N. Pavel, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, A. Margotti, A. Montanari, R. Nania, F. Palmonari, A. Pesci, L. Rinaldi Nov 2004

Substructure Dependence Of Jet Cross Sections At Hera And Determination Of ΑS, S. Chekanov, M. Derrick, J. H. Loizides, S. Magill, S. Miglioranzi, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, N. Pavel, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, A. Margotti, A. Montanari, R. Nania, F. Palmonari, A. Pesci, L. Rinaldi

Faculty Publications

No abstract provided.

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The Origin Of Fe Ii Emission In Active Galactic Nuclei, J. A. Baldwin, Gary J. Ferland, K. T. Korista, F. Hamann, A. Lacluyzé Nov 2004

The Origin Of Fe Ii Emission In Active Galactic Nuclei, J. A. Baldwin, Gary J. Ferland, K. T. Korista, F. Hamann, A. Lacluyzé

Physics and Astronomy Faculty Publications

We used a very large set of models of broad emission line region (BELR) clouds in active galactic nuclei to investigate the formation of the observed Fe II emission lines. We show that photoionized BELR clouds cannot produce both the observed shape and observed equivalent width of the 2200-2800 Å Fe II UV bump unless there is considerable velocity structure corresponding to a microturbulent velocity parameter vturb≥100 km s-1 for the locally optimally emitting cloud models used here. This could be either microturbulence in gas that is confined by some phenomenon such as MHD waves or a …

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Geometric Acoustic Modeling Of The Lds Conference Center, Heather Smith Nov 2004

Geometric Acoustic Modeling Of The Lds Conference Center, Heather Smith

Theses and Dissertations

This thesis discusses the process of modeling a 21,000 seat fan-shaped auditorium using methods of geometric acoustics. Two commercial geometric acoustics software packages were used in the research: CATT-Acoustic™ 8.0 and EASE™ 4.1. The process first included creating preliminary models of the hall using published absorption coefficients for its surfaces and approximate scattering coefficients based on current best-known techniques. A detailed analysis determined the minimum numbers of rays needed in both packages to produce reliable results with these coefficient values. It was found that 100,000 rays were needed for CATT™ and 500,000 rays were needed for EASE™. Analysis was also …

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Theoretical Study Of The Magnetic Ordering In Rare-Earth Compounds With Face-Centered-Cubic Structure, Chun-Gang Duan, Renat F. Sabirianov, Jianjun Liu, Wai-Ning Mei, Peter A. Dowben, John R. Hardy Nov 2004

Theoretical Study Of The Magnetic Ordering In Rare-Earth Compounds With Face-Centered-Cubic Structure, Chun-Gang Duan, Renat F. Sabirianov, Jianjun Liu, Wai-Ning Mei, Peter A. Dowben, John R. Hardy

Peter Dowben Publications

We present a detailed theoretical study of the magnetic ordering in heavy rare-earth compounds with a face-centered-cubic structure. In addition to the exchange interactions which are counted up to the third nearest neighbors, the effect of the dipolar interactions and magnetic anisotropic effect are also included in our model Hamiltonian. The interactions parameters are obtained from first-principles band-structure calculations by fitting the total energies of different magnetic configurations to the Heisenberg Model. Thus from utilizing the Monte Carlo simulations, we explained the formation of different magnetic structures in the rare-earth compounds.

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Noncollinear Spin States And Competing Interactions In Half-Metals, Ralph Skomski, Jian Zhou, Peter A. Dowben, David J. Sellmyer Nov 2004

Noncollinear Spin States And Competing Interactions In Half-Metals, Ralph Skomski, Jian Zhou, Peter A. Dowben, David J. Sellmyer

Peter Dowben Publications

The high-field spin structure of magnetic perovskites and related magnetoresistive materials is investigated by model calculations. Competing exchange as well as real-structure-dependent random field, random anisotropy, and Dzyaloshinskii–Moriya interactions yield a noncollinear magnetic structure that may be called a spin colloid. The noncollinear structure, which contributes to the zero- and finite-temperature spin mixing and reduces the magnetoresistance, is strongly field dependent. © 2005 American Institute of Physics. [DOI: 10.1063/1.1851412]

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A Geometrical Approach To N=2 Super Yang-Mills Theory On The Two Dimensional Lattice, Simon Catterall Nov 2004

A Geometrical Approach To N=2 Super Yang-Mills Theory On The Two Dimensional Lattice, Simon Catterall

Physics - All Scholarship

We propose a discretization of two dimensional Euclidean Yang-Mills theories with N=2 supersymmetry which preserves exactly both gauge invariance and an element of supersymmetry. The approach starts from the twisted form of the continuum super Yang Mills action which we show may be written in terms of two real Kahler-Dirac fields whose components transform into each other under the twisted supersymmetry. Once the theory is written in this geometrical language it is straightforward to discretize by mapping the component tensor fields to appropriate geometrical structures in the lattice and by replacing the continuum exterior derivative and its adjoint by appropriate …

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Disorder-Induced Depression Of The Curie Temperature In Mechanically Milled Gdal2, Marco Morales Torres, D. S. Williams, P. M. Shand, C. Stark, T. M. Pekarek, Lanping Yue, V. Petkov, Diandra Leslie-Pelecky Nov 2004

Disorder-Induced Depression Of The Curie Temperature In Mechanically Milled Gdal2, Marco Morales Torres, D. S. Williams, P. M. Shand, C. Stark, T. M. Pekarek, Lanping Yue, V. Petkov, Diandra Leslie-Pelecky

Diandra Leslie-Pelecky Publications

The effect of disorder on the ferromagnetic transition is investigated in mechanically milled GdAl2. GdAl2 is a ferromagnet when crystalline and a spin glass when amorphous. Mechanical milling progressively disorders the alloy, allowing observation of the change from ferromagnetic to a disordered magnetic state. X-ray diffraction and pair-distribution-function analysis are used to determine the grain size, lattice parameter, and mean-squared atomic displacements. The magnetization as a function of temperature is described by a Gaussian distribution of Curie temperatures. The mean Curie temperature decreases with decreasing lattice parameter, where lattice parameter serves as a measure of defect concentration. …

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Direct Comparison Between Phase Locked Oscillator And Direct Resonance Oscillator In The Noncontact Atomic Force Microscopy Under Ultrahigh Vacuum, Byung I. Kim Nov 2004

Direct Comparison Between Phase Locked Oscillator And Direct Resonance Oscillator In The Noncontact Atomic Force Microscopy Under Ultrahigh Vacuum, Byung I. Kim

Physics Faculty Publications and Presentations

I have demonstrated the advantage of the phase locked oscillator (PLO) over the conventional direct resonance oscillator (DRO) in noncontact mode atomic force microscopy (AFM) under ultrahigh vacuum. Direct comparison between PLO and DRO has been made in terms of background noise level, temporal response, and stability. Compared to the DRO method without phase coherence, the experimental results show that the PLO method is more effective in reducing the noise level and enhancing the stability over all force regimes in UHV noncontact AFM. The noise reduction and stability enhancement in PLO indicate the important role of the phase coherent effect …

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Theoretical Study Of The Magnetic Ordering In Rare-Earth Compounds With Face-Centered-Cubic Structure, Chun-Gang Duan, Renat F. Sabirianov, Jianjun Liu, Wai-Ning Mei, Peter A. Dowben, John R. Hardy Nov 2004

Theoretical Study Of The Magnetic Ordering In Rare-Earth Compounds With Face-Centered-Cubic Structure, Chun-Gang Duan, Renat F. Sabirianov, Jianjun Liu, Wai-Ning Mei, Peter A. Dowben, John R. Hardy

Physics Faculty Publications

We present a detailed theoretical study of the magnetic ordering in heavy rare-earth compounds with a face-centered-cubic structure. In addition to the exchange interactions which are counted up to the third nearest neighbors, the effect of the dipolar interactions and magnetic anisotropic effect are also included in our model Hamiltonian. The interactions parameters are obtained from first-principles band-structure calculations by fitting the total energies of different magnetic configurations to the Heisenberg Model. Thus from utilizing the Monte Carlo simulations, we explained the formation of different magnetic structures in the rare-earth compounds.

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The Dynamics And Tuning Of Orchestral Crotales, Bradley M. Deutsch, Cherie L. Ramirez, Thomas R. Moore Nov 2004

The Dynamics And Tuning Of Orchestral Crotales, Bradley M. Deutsch, Cherie L. Ramirez, Thomas R. Moore

Student-Faculty Collaborative Research Publications

Crotales are center-weighted, tuned cymbals that are found in the percussion section of most orchestras. They are arranged like a keyboard in octave sets and are commercially available in two octaves, from C6 to C8. Little information about the physics of crotales has been reported in the literature, despite their having the interesting property of producing a particularly pleasing sound. In this study, the acoustic and vibrational properties of crotales from C6 to C8 are theoretically and experimentally investigated. Interferograms of typical vibrational modes are presented, and the frequencies of the acoustically important modes of crotales are identified and reported. …

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Light Hadrons With Improved Staggered Quarks: Approaching The Continuum Limit, James E. Hetrick, C. Aubin Nov 2004

Light Hadrons With Improved Staggered Quarks: Approaching The Continuum Limit, James E. Hetrick, C. Aubin

All Faculty Articles - School of Engineering and Computer Science

We have extended our program of QCD simulations with an improved Kogut-Susskind quark action to a smaller lattice spacing, approximately 0.09 fm. Also, the simulations with a ≈ 0.12 fm have been extended to smaller quark masses. In this paper we describe the new simulations and computations of the static quark potential and light hadron spectrum. These results give information about the remaining dependences on the lattice spacing. We examine the dependence of computed quantities on the spatial size of the lattice, on the numerical precision in the computations, and on the step size used in the numerical integrations. We …

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Light Pseudoscalar Decay Constants, Quark Masses, And Low Energy Constants From Three Flavor Lattice Qcd, James E. Hetrick, C. Aubin Nov 2004

Light Pseudoscalar Decay Constants, Quark Masses, And Low Energy Constants From Three Flavor Lattice Qcd, James E. Hetrick, C. Aubin

All Faculty Articles - School of Engineering and Computer Science

As part of our program of lattice simulations of three-flavor QCD with improved staggered quarks, we have calculated pseudoscalar meson masses and decay constants for a range of valence quark masses and sea-quark masses on lattices with lattice spacings of about 0.125 and 0.09 fm. We fit the lattice data to forms computed with “staggered chiral perturbation theory.” Our results provide a sensitive test of the lattice simulations, and especially of the chiral behavior, including the effects of chiral logarithms. We find: fπ = 129.5 ± 0.9 ± 3.5 MeV, fK = 156.6 ± 1.0 ± 3.6 MeV, and fK/ …

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Relaxation To Native Conformation Of A Bond-Fluctuating Protein Chain With Hydrophobic And Polar Nodes, Johan Bjursell, Ras B. Pandey Nov 2004

Relaxation To Native Conformation Of A Bond-Fluctuating Protein Chain With Hydrophobic And Polar Nodes, Johan Bjursell, Ras B. Pandey

Faculty Publications

The conformation and dynamics of a protein chain with hydrophobic and polar nodes are examined by the bond-fluctuation model using Monte Carlo simulations on a cubic lattice. The minimal (nearest neighbor) interaction leads to standard (self-avoiding walk) conformation, i.e., the scaling of the radius of gyration Rg with the molecular weight N Rg ∝ Nγ with γ ≃ 3/5/ Specific interactions with longer range and higher strength are needed to approach the native globular conformations with γ < 3/5. Relaxation into the globular ground state shows a weak power-law decay, i.e., Rg ∝ t-α, α ~ 0.06-0.12.

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Two-Loop Bethe Logarithms For Higher Excited S Levels, Ulrich D. Jentschura Nov 2004

Two-Loop Bethe Logarithms For Higher Excited S Levels, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

Processes mediated by two virtual low-energy photons contribute quite significantly to the energy of hydrogenic S states. The corresponding level shift is of the order of ( α / π )2 ( Z α )6 mec2 and may be ascribed to a two-loop generalization of the Bethe logarithm. For 1 S and 2 S states, the correction has recently been evaluated by Pachucki and Jentschura [Phys. Rev. Lett. 91, 113005 (2003)]. Here, we generalize the approach to higher excited S states, which in contrast to the 1 S and 2 S states can decay to …

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Nucleation Rates Of Water And Heavy Water Using Equations Of State, Abdalla Obeidat, Jin-Song Li, Gerald Wilemski Nov 2004

Nucleation Rates Of Water And Heavy Water Using Equations Of State, Abdalla Obeidat, Jin-Song Li, Gerald Wilemski

Physics Faculty Research & Creative Works

The original formula of Gibbs for the reversible work of critical nucleus formation is evaluated in three approximate ways for ordinary and heavy water. The least approximate way employs an equation of state to evaluate the pressure difference between the new and old phases. This form of the theory yields a temperature dependence for the nucleation rate close to that observed experimentally. This is a substantial improvement over the most commonly used (and most approximate) form of classical theory.©2004 American Institute of Physics.

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Computing The M = 1 Diocotron Frequency Via An Equilibrium Calculation In Non-Neutral Plasmas, Ross L. Spencer Oct 2004

Computing The M = 1 Diocotron Frequency Via An Equilibrium Calculation In Non-Neutral Plasmas, Ross L. Spencer

Faculty Publications

The m = 1 diocotron mode in non-neutral plasmas has long been thought of as a shifted equilibrium, and its frequency has been approximately calculated in this way by Fine and Driscoll [Phys. Plasmas 5, 601 (1998)]. This article shows that this idea can be coupled with a standard axisymmetric equilibrium calculation on a grid to calculate the frequency of this mode to very high precision including both finite-length and thermal effects, provided that the Debye length is small enough. As the Debye length begins to approach the plasma size not only does the shifted equilibrium calculation fail to predict …

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Direct Photon Cross Section With Conversions At Cdf, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Oct 2004

Direct Photon Cross Section With Conversions At Cdf, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present a measurement of the isolated direct photon cross section in pp̅ collisions at √s =1.8 TeV and |η|0→γγ and η→γγ events from the data we use a new background subtraction technique which takes advantage of the tracking information available in a photon conversion event. We find that the shape of the cross section as a function of photon pT is poorly described by next-to-leading-order QCD predictions, but agrees with previous CDF measurements.

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Observation And Properties Of The X(3872) Decaying To J/Ψπ+Π- In Pp̅ Collisions At √S = 1.96 Tev, V. M. Abazov, Gregory R. Snow, D0 Collaboration Oct 2004

Observation And Properties Of The X(3872) Decaying To J/Ψπ+Π- In Pp̅ Collisions At √S = 1.96 Tev, V. M. Abazov, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

We report the observation of the X(3872) in the J/ψπ+π- channel, with J/ψ decaying to μ+μ-, in pp̅ collisions at √s = 1.96 TeV. Using approximately 230 pb-1 of data collected with the Run II D0 detector, we observe 522 ± 100 X(3872) candidates. The mass difference between the X(3872) state and the J=J/ψ is measured to be 774.9 ± 3.1(stat) ± 3.0(syst) MeV/c2. We have investigated the production and decay characteristics of the X(3872) and find them to be …

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Underlying Event In Hard Interactions At The Fermilab Tevatron P̅P Collider, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Oct 2004

Underlying Event In Hard Interactions At The Fermilab Tevatron P̅P Collider, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

For comparison of inclusive jet cross sections measured at hadron-hadron colliders to next-to-leading order (NLO) parton-level calculations, the energy deposited in the jet cone by spectator parton interactions must first be subtracted. The assumption made at the Tevatron is that the spectator parton interaction energy is similar to the ambient level measured in minimum bias events. In this paper, we test this assumption by measuring the ambient charged track momentum in events containing large transverse energy jets at √s =1800 GeV and √s =630 GeV and comparing this ambient momentum with that observed both in minimum bias events and with …

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Photon And Neutral Pion Production In Au+Au Collisions At √SNn=130 Gev, Star Collaboration, T.D. Gutierrez Oct 2004

Photon And Neutral Pion Production In Au+Au Collisions At √SNn=130 Gev, Star Collaboration, T.D. Gutierrez

Physics

We report inclusive photon measurements about midrapidity (∣y∣<0.5) from 197Au+197Au collisions at √sNN=130 GeV at RHIC. Photon pair conversions were reconstructed from electron and positron tracks measured with the Time Projection Chamber (TPC) of the STAR experiment. With this method, an energy resolution of ΔE ∕ E≈2% at 0.5GeV has been achieved. Reconstructed photons have also been used to measure the transverse momentum (pt) spectra of π0mesons about midrapidity (∣y∣<1) via the π0→γγ decay channel. The fractional contribution of the π0→γγ decay to the inclusive photon spectrum decreases by 20%±5% between pt …

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Rapidity And Centrality Dependence Of Proton And Antiproton Production From 197Au + 197Au Collisions At √SNn=130 Gev, Star Collaboration, T.D. Gutierrez Oct 2004

Rapidity And Centrality Dependence Of Proton And Antiproton Production From 197Au + 197Au Collisions At √SNn=130 Gev, Star Collaboration, T.D. Gutierrez

Physics

We report on the rapidity and centrality dependence of proton and antiproton transverse mass distributions from 197Au+197Au collisions at √sNN=130 GeV as measured by the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). Our results are from the rapidity and transverse momentum range of ∣y∣<0.5 and 0.35 < pt < 1.00 GeV ∕ c. For both protons and antiprotons, transverse mass distributions become more convex from peripheral to central collisions demonstrating characteristics of collective expansion. The measured rapidity distributions and the mean transverse momenta versus rapidity are flat within ∣y∣<0.5. Comparisons of our data with results from model calculations indicate that in order to obtain a consistent picture of the proton (antiproton) yields and transverse mass distributions the possibility of prehadronic collective expansion may have to be taken into account.

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Centrality And Pseudorapidity Dependence Of Charged Hadron Production At Intermediate PT In Au+Au Collisions At √SNn=130 Gev, Star Collaboration, T.D. Gutierrez Oct 2004

Centrality And Pseudorapidity Dependence Of Charged Hadron Production At Intermediate PT In Au+Au Collisions At √SNn=130 Gev, Star Collaboration, T.D. Gutierrez

Physics

We present STAR measurements of charged hadron production as a function of centrality in Au+Au collisions at √sNN=130 GeV. The measurements cover a phase space region of 0.2T<6.0GeV∕c in transverse momentum and −1<η<1 in pseudorapidity. Inclusive transverse momentum distributions of charged hadrons in the pseudorapidity region 0.5<∣η∣<1 are reported and compared to our previously published results for ∣η∣<0.5. No significant difference is seen for inclusive pT distributions of charged hadrons in these two pseudorapidity bins. We measured dN∕dη distributions and truncated mean pT in a region of pT>pTcut, and studied the results in the framework of participant and binary scaling. No clear evidence is observed for participant scaling of charged hadron yield in the measured pT region. The relative importance of hard scattering processes is investigated through binary …

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Analysis And Comparison Of Three Acoustic Energy Density Probes, Lance Lester Locey Oct 2004

Analysis And Comparison Of Three Acoustic Energy Density Probes, Lance Lester Locey

Theses and Dissertations

Traditional methods for the investigation of sound fields generally rely on a microphone to convert sound pressure into an electrical signal which can be recorded, displayed, and so forth. The squared sound pressure is directly related to potential energy density. Consequently, the measurement of sound pressure alone does not inherently provide insight into the total energy density of the sound field. Specifically, no information about the kinetic energy density of the sound field is available from this measurement alone. However, it is possible to use two microphones to estimate particle velocity. The squared particle velocity magnitude is directly related to …

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Stabilizing Moduli With String Cosmology, Scott Watson Oct 2004

Stabilizing Moduli With String Cosmology, Scott Watson

Physics - All Scholarship

In this talk I will discuss the role of finite temperature quantum corrections in string cosmology and show that they can lead to a stabilization mechanism for the volume moduli. I will show that from the higher dimensional perspective this results from the effect of states of enhanced symmetry on the one-loop free energy. These states lead not only to stabilization, but also suggest an alternative model for cold dark matter. At late times, when the low energy effective field theory gives the appropriate description of the dynamics, the moduli will begin to slow-roll and stabilization will generically fail. However, …

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Wide Angle Decentered Lens Beam Steering For Infrared Countermeasures Applications, Jennifer L. Gibson, Bradley D. Duncan, Edward A. Watson, John S. Loomis Oct 2004

Wide Angle Decentered Lens Beam Steering For Infrared Countermeasures Applications, Jennifer L. Gibson, Bradley D. Duncan, Edward A. Watson, John S. Loomis

Electro-Optics and Photonics Faculty Publications

A beam-steering system consisting of three cemented achromatic doublets is presented. Intended for use in IR countermeasure applications, our system is designed to operate over the 2- to 5-μm spectrum with minimum angular dispersion. We show that dispersion can be minimized by using doublet lenses fashioned from AMTIR-1 and germanium. Our system is designed to be compact and lightweight, with no internal foci, while allowing steering to ±22.5 deg. We also maintain a minimum 2-in. clear aperture for all steering angles, and a nominal divergence of 1 mrad. Plane wave and Gaussian beam analyses of our system are presented.

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