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2005

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Articles 31 - 60 of 738

Full-Text Articles in Physics

Percolation Quantum Phase Transitions In Diluted Magnets, Thomas Vojta, Jörg Schmalian Nov 2005

Percolation Quantum Phase Transitions In Diluted Magnets, Thomas Vojta, Jörg Schmalian

Physics Faculty Research & Creative Works

We show that the interplay of geometric criticality and quantum fluctuations leads to a novel universality class for the percolation quantum phase transition in diluted magnets. All critical exponents involving dynamical correlations are different from the classical percolation values, but in two dimensions they can nonetheless be determined exactly. We develop a complete scaling theory of this transition, and we relate it to recent experiments in La2Cu1-p(Zn,Mg)pO4. Our results are also relevant for disordered interacting boson systems.

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Dynamics Of A Nanomechanical Resonator Coupled To A Superconducting Single-Electron Transistor, M. P. Blencowe, J. Imbers, A. D. Armour Nov 2005

Dynamics Of A Nanomechanical Resonator Coupled To A Superconducting Single-Electron Transistor, M. P. Blencowe, J. Imbers, A. D. Armour

Dartmouth Scholarship

We present an analysis of the dynamics of a nanomechanical resonator coupled to a superconducting single-electron transistor (SSET) in the vicinity of Josephson quasi-particle (JQP) and double Josephson quasi-particle (DJQP) resonances. For weak coupling and wide separation of dynamical timescales, we find that for either superconducting resonances the dynamics of the resonator are given by a Fokker–Planck equation, i.e. the SSET behaves effectively as an equilibrium heat bath, characterized by an effective temperature, which also damps the resonator and renormalizes its frequency. Depending on the gate and drain–source voltage bias points with respect to the superconducting resonance, the SSET can …

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Fluorescence Measurements Of Expanding Strongly Coupled Neutral Plasmas, E. A. Cummings, J. E. Daily, Dallin S. Durfee, Scott D. Bergeson Nov 2005

Fluorescence Measurements Of Expanding Strongly Coupled Neutral Plasmas, E. A. Cummings, J. E. Daily, Dallin S. Durfee, Scott D. Bergeson

Faculty Publications

We report new detailed density profile measurements in expanding strongly coupled neutral calcium plasmas. Using laser-induced fluorescence techniques, we determine plasma densities in the range of 10^5 to 10^9 cm^-3 with a time resolution limit as small as 7 ns. Strong coupling in the plasma ions is inferred directly from the fluorescence signals. Evidence for strong coupling at late times is presented, confirming a recent theoretical result.

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Reversible Hysteresis Loop Tuning, Andreas Berger, Christian Binek, D. T. Margulies, A. Moser, E. E. Fullerton Nov 2005

Reversible Hysteresis Loop Tuning, Andreas Berger, Christian Binek, D. T. Margulies, A. Moser, E. E. Fullerton

Christian Binek Publications

We utilize antiferromagnetically coupled bilayer structures to magnetically tune hysteresis loop properties. Key element of this approach is the non-overlapping switching fi eld distribution of the two magnetic layers that make up the system: a hard magnetic CoPtCrB layer (HL) and a soft magnetic CoCr layer (SL). Both layers are coupled antiferromagnetically through an only 0.6-nm-thick Ru interlayer. The nonoverlapping switching fi eld distribution allows the measurement of magnetization reversal in the SL at low fi elds while keeping the magnetization state of the HL unperturbed. Applying an appropriate high fi eld or high fi eld sequence changes the magnetic …

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Ferroelectric Switch For Spin Injection, Mikhail Y. Zhuravlev, Sitaram Jaswal, Evgeny Y. Tsymbal, Renat F. Sabirianov Nov 2005

Ferroelectric Switch For Spin Injection, Mikhail Y. Zhuravlev, Sitaram Jaswal, Evgeny Y. Tsymbal, Renat F. Sabirianov

Physics Faculty Publications

A method for the switching of the spin polarization of the electric current injected into a semiconductor is proposed, based on injecting spins from a diluted magnetic semiconductor through a ferroelectric tunnel barrier. We show that the reversal of the electric polarization of the ferroelectric results in a sizable change in the spin polarization of the injected current, thereby providing a two-state electrical control of this spintronic device. We also predict a possibility of switching of tunneling magnetoresistance in magnetic tunnel junctions with a ferroelectric barrier and coexistence of tunneling magnetoresistance and giant electroresistance effects in these multiferroic tunnel junctions.

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Inclusive Jet Cross Sections And Dijet Correlations In D*± Photoproduction At Hera, S. Chekanov, M. Derrick, S. Magill, S. Miglioranzi, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, N. Pavel, A. G. Yagües Molina, 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, A. Polini Nov 2005

Inclusive Jet Cross Sections And Dijet Correlations In D*± Photoproduction At Hera, S. Chekanov, M. Derrick, S. Magill, S. Miglioranzi, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, N. Pavel, A. G. Yagües Molina, 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, A. Polini

Faculty Publications

Inclusive jet cross sections in photoproduction for events containing a D* meson have been measured with the ZEUS detector at HERA using an integrated luminosity of 78.6 pb-1. The events were required to have a virtuality of the incoming photon, Q2, of less than 1 GeV2, and a photon-proton centre-of-mass energy in the range 130 < Wγp < 280 GeV. The measurements are compared with next-to-leading-order (NLO) QCD calculations. Good agreement is found with the NLO calculations over most of the measured kinematic region. Requiring a second jet in the event allowed a more detailed comparison with QCD calculations. The measured dijet cross sections are also compared to Monte Carlo (MC) models which incorporate leading-order matrix elements followed by parton showers and hadronisation. The NLO QCD predictions are in general agreement with the data although differences have been isolated to regions where contributions from higher orders are expected to be significant. The MC models give a better description than the NLO predictions of the shape of the measured cross sections. © 2005 Elsevier B.V. All rights reserved.

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Search For BS0→Μ+Μ- And BD0→Μ+Μ- Decays In PΡ̅ Collisions With Cdf Ii, A. Abulencia, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Nov 2005

Search For BS0→Μ+Μ- And BD0→Μ+Μ- Decays In PΡ̅ Collisions With Cdf Ii, A. Abulencia, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We report on a search for Bs0→µ+µ- and Bd0→µ+µ- decays in pρ̅ collisions at √8=1.96 TeV using 364 pb-1 of data collected by the CDF II detector at the Fermilab Tevatron Collider. After applying all selection requirements, we observe no candidates inside the Bs0 or Bd0 mass windows. The resulting upper limits on the branching fractions are Ɓ (Bs0→µ+µ-)<1.5×10-7 and Ɓ (Bd0→µ+µ-)<3.9×10-8 at 90% confidence level.

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Performance Of A C4f8o Gas Radiator Ring Imaging Cherenkov Detector Using Multi-Anode Photomultiplier Tubes, Raymond Mountain, Marina Artuso, Chaouki Boulahouache, S. Blusk Nov 2005

Performance Of A C4f8o Gas Radiator Ring Imaging Cherenkov Detector Using Multi-Anode Photomultiplier Tubes, Raymond Mountain, Marina Artuso, Chaouki Boulahouache, S. Blusk

Physics - All Scholarship

We report on test results of a novel ring imaging Cherenkov (RICH) detection system consisting of a 3 meter long gaseous C4F8O radiator, a focusing mirror, and a photon detector array based on Hamamatsu multi-anode photomultiplier tubes. This system was developed to identify charged particles in the momentum range from 3-70 GeV/c for the BTeV experiment.

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Acoustics Of The Salt Lake Tabernacle: Characterization And Study Of Spatial Variation, Sarah Rollins Nov 2005

Acoustics Of The Salt Lake Tabernacle: Characterization And Study Of Spatial Variation, Sarah Rollins

Theses and Dissertations

In order to preserve the acoustics of the Salt Lake Tabernacle after the seismic renovation of 2005-2006, it was necessary to characterize these acoustics immediately preceding the renovation. This thesis discusses the characterization process that began with the measurement of hundreds of impulse responses for five different source positions and several receiver locations throughout the hall seating areas. The acoustics were further characterized by deriving various parameters from these responses that correlate with subjective preferences for music and speech. Impulse responses were also generated by a CATT-Acoustic™ computer model of the Tabernacle for the same purpose. The parameter values were …

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Charge-Exchange Spectra Of Hydrogenic And He-Like Iron, B. J. Wargelin, P. Beiersdorfer, P. A. Neill, Ronald E. Olson, J. H. Scofield Nov 2005

Charge-Exchange Spectra Of Hydrogenic And He-Like Iron, B. J. Wargelin, P. Beiersdorfer, P. A. Neill, Ronald E. Olson, J. H. Scofield

Physics Faculty Research & Creative Works

We present H-like Fe XXVI and He-like Fe XXV charge-exchange spectra resulting from collisions of highly charged iron with N2 gas at an energy of ∼10 eV amu-1 in an electron beam ion trap. Although individual high-n emission lines are not resolved in our measurements, we observe that the most likely level for Fe+25 → Fe+24 electron capture is nmax ∼ 9, in line with expectations, while the most likely value for Fe+26 → Fe+25 charge exchange is significantly higher. in the Fe XXV spectrum, the Kα emission feature dominates, whether produced via charge exchange …

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Low Magnetic Prandtl Number Dynamos With Helical Forcing, Pablo D. Mininni, David C. Montgomery Nov 2005

Low Magnetic Prandtl Number Dynamos With Helical Forcing, Pablo D. Mininni, David C. Montgomery

Dartmouth Scholarship

We present direct numerical simulations of dynamo action in a forced Roberts flow. The behavior of the dynamo is followed as the mechanical Reynolds number is increased, starting from the laminar case until a turbulent regime is reached. The critical magnetic Reynolds for dynamo action is found, and in the turbulent flow it is observed to be nearly independent on the magnetic Prandtl number in the range from ∼0.3 to ∼0.1. Also the dependence of this threshold with the amount of mechanical helicity in the flow is studied. For the different regimes found, the configuration of the magnetic and velocity …

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Nanomesa And Nanowell Formation In Langmuir–Blodgett Polyvinylidene Fluoride Trifluoroethylene Copolymer Films, Jiangyu Li, Yang Luo, Mengjun Bai, Stephen Ducharme Nov 2005

Nanomesa And Nanowell Formation In Langmuir–Blodgett Polyvinylidene Fluoride Trifluoroethylene Copolymer Films, Jiangyu Li, Yang Luo, Mengjun Bai, Stephen Ducharme

Department of Physics and Astronomy: Faculty Publications

In this letter, we report an energetics-based model to explain the self-organizing nanomesa and nanowell patterns recently observed in Langmuir-Blodgett (LB) films of polyvinylidene fluoride trifluoroethylene [P(VDF-TrFE)] copolymers. The feature size of nanomesas and nanowells has been estimated using a linear stability analysis, and the morphology of the nanomesas and nanowells has been revealed by the numerical simulation, both in good agreement with experiments. A number of other model predictions regarding the nanomesa and nanowell formation also agree with experimental observations. The model can be used to guide the design and optimization of nanostructures in the P(VDF-TrFE) LB films and …

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Progress Towards Terahertz Acoustic Phonon Generation In Doping Superlattices, Thomas E. Wilson Nov 2005

Progress Towards Terahertz Acoustic Phonon Generation In Doping Superlattices, Thomas E. Wilson

Physics Faculty Research

Progress is described in experiments to generate coherent terahertz acoustic phonons in silicon doping superlattices by the resonant absorption of nanosecond-pulsed far-infrared laser radiation. Future experiments are proposed that would use the superlattice as a transducer in a terahertz cryogenic acoustic reflection microscope with sub-nanometer resolution.

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Pumping Or Mixing System Using A Levitating Magnetic Element, Aexandre N. Terentiev Nov 2005

Pumping Or Mixing System Using A Levitating Magnetic Element, Aexandre N. Terentiev

Physics and Astronomy Faculty Patents

A system capable of pumping or mixing fluids using a rotating magnetic element or bearing levitated by a cold superconducting element is disclosed.

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Combination Of Cdf And D0 Results On The W Boson Mass And Width, V. M. Abazov, Gregory Snow, D0 Collaboration Nov 2005

Combination Of Cdf And D0 Results On The W Boson Mass And Width, V. M. Abazov, Gregory Snow, D0 Collaboration

Gregory Snow 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 …

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Photovoltaic Effect In Bent Quantum Wires In The Ballistic Transport Regime, Yuriy V. Pershin Dr, Carlo Piermarocchi Nov 2005

Photovoltaic Effect In Bent Quantum Wires In The Ballistic Transport Regime, Yuriy V. Pershin Dr, Carlo Piermarocchi

Faculty Publications

A scheme for the generation of a photocurrent in bent quantum wires is proposed. We calculate the current using a generalized Landauer-Büttiker approach that takes into account the electromagnetic radiation. For circularly polarized light, it is demonstrated that the curvature in the bent wire induces an asymmetry in the scattering coefficients for left and right moving electrons. This asymmetry results in a current at zero bias voltage. The effect is due to the geometry of the wire which transforms the photon angular momentum into translational motion for the electrons. Possible experimental realizations of this scheme are discussed.

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Parametrizations And Dynamical Analysis Of Angle-Integrated Cross Sections For Double Photoionization Including Nondipole Effects, Andrei Y. Istomin, Anthony F. Starace, N. L. Manakov, A. V. Meremianin, A. S. Kheifets, Igor Bray Nov 2005

Parametrizations And Dynamical Analysis Of Angle-Integrated Cross Sections For Double Photoionization Including Nondipole Effects, Andrei Y. Istomin, Anthony F. Starace, N. L. Manakov, A. V. Meremianin, A. S. Kheifets, Igor Bray

Department of Physics and Astronomy: Faculty Publications

Similarly to differential cross sections for one-electron photoionization, the doubly differential cross section for double photoionization (DPI) may be conveniently described by four parameters: the singly differential (with respect to energy sharing) cross section (sigma0), the dipole asymmetry parameter (beta), and two nondipole asymmetry parameters (gamma and delta). Here we derive two model-independent representations for these parameters for DPI from a 1S0 atomic bound state: (i) in terms of one-dimensional integrals of the polarization-invariant DPI amplitudes and (ii) in terms of the exact two-electron reduced matrix elements. For DPI of He at excess energies, Eexc, of 100 eV, 450 eV, …

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Nonlinear All-Optical Gan/Algan Multi-Quantum-Well Devices For 100 Gb/S Applications At Λ = 1.55 Μm, Greg Sun, Jacob B. Khurgin, Richard A. Soref Nov 2005

Nonlinear All-Optical Gan/Algan Multi-Quantum-Well Devices For 100 Gb/S Applications At Λ = 1.55 Μm, Greg Sun, Jacob B. Khurgin, Richard A. Soref

Physics Faculty Publications

Using quantum-mechanical analysis, a strain-balanced stack of coupled GaN/AlGaNquantum wells has been engineered for bandwidth-optimized all-optical switching at low switching powers. Intersubband transitions between three conduction subbands provide the basis for the large, fast, nonlinear optical response. Optimized performance for a given symbol rate is obtained by engineering the response time and nonlinear phase shift.

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Using Ultrasonic Atomization To Produce An Aerosol Of Micron-Scale Particles, Thomas D. Donnelly, J. Hogan '03, A. Mugler '04, M. Schubmehl '02, N. Schommer '04, Andrew J. Bernoff, S. Dasnurkar, T. Ditmire Nov 2005

Using Ultrasonic Atomization To Produce An Aerosol Of Micron-Scale Particles, Thomas D. Donnelly, J. Hogan '03, A. Mugler '04, M. Schubmehl '02, N. Schommer '04, Andrew J. Bernoff, S. Dasnurkar, T. Ditmire

All HMC Faculty Publications and Research

A device that uses ultrasonic atomization of a liquid to produce an aerosol of micron-scale droplets is described. This device represents a new approach to producing targets relevant to laser-driven fusion studies, and to rare studies of nonlinear optics in which wavelength-scale targets are irradiated. The device has also made possible tests of fluid dynamics models in a novel phase space. The distribution of droplet sizes produced by the device and the threshold power required for droplet production are shown to follow scaling laws predicted by fluid dynamics.

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Effects Of Disorder On Electron Transport In Arrays Of Quantum Dots, Alan Middleton, Shantenu Jha Nov 2005

Effects Of Disorder On Electron Transport In Arrays Of Quantum Dots, Alan Middleton, Shantenu Jha

Physics - All Scholarship

We investigate the zero-temperature transport of electrons in a model of quantum dot arrays with a disordered background potential. One effect of the disorder is that conduction through the array is possible only for voltages across the array that exceed a critical voltage $V_T$. We investigate the behavior of arrays in three voltage regimes: below, at and above the critical voltage. For voltages less than $V_T$, we find that the features of the invasion of charge onto the array depend on whether the dots have uniform or varying capacitances. We compute the first conduction path at voltages just above $V_T$ …

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Laser-Powered Thermoelectric Generators Operating At Cryogenic Temperatures, S. R. Harutyunyan, V. H. Vardanyan, A. S. Kuzanyan, V. R. Nikoghosyan, S. Kunii, K. Winzer, K. S. Wood, Armen Gulian Nov 2005

Laser-Powered Thermoelectric Generators Operating At Cryogenic Temperatures, S. R. Harutyunyan, V. H. Vardanyan, A. S. Kuzanyan, V. R. Nikoghosyan, S. Kunii, K. Winzer, K. S. Wood, Armen Gulian

Mathematics, Physics, and Computer Science Faculty Articles and Research

A thermoelectric generator, operating in a cryostat at liquid helium temperatures, is described. Energy to the generator is supplied via an external laser beam. For this prototype device the associated heat load at permanent operation is comparable with the heat load associated with power delivery via metallic wires. Estimates indicate that still better performance can be enabled with existing thermoelectric materials, thereby far exceeding efficiency of traditional cryostat wiring. We used a prototype generator to produce electric power for measuring critical currents in Nb3Sn-films at 4K.

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Spontaneous Lorentz Violation And Nonpolynomial Interactions, Brett Altschul, V. Alan Kostelecký Nov 2005

Spontaneous Lorentz Violation And Nonpolynomial Interactions, Brett Altschul, V. Alan Kostelecký

Faculty Publications

Gauge-noninvariant vector field theories with superficially nonrenormalizable nonpolynomial interactions are studied. We show that nontrivial relevant and stable theories have spontaneous Lorentz violation, and we present a large class of asymptotically free theories. The Nambu-Goldstone modes of these theories can be identified with the photon, with potential experimental implications. © 2005 Elsevier B.V. All rights reserved.

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Observations And Analysis Of Uncorrelated Rain, Michael L. Larsen, Alexander Kostinski, Ali Tokay Nov 2005

Observations And Analysis Of Uncorrelated Rain, Michael L. Larsen, Alexander Kostinski, Ali Tokay

Department of Physics Publications

Most microphysical models in precipitation physics and radar meteorology assume (at least implicitly) that raindrops are completely uncorrelated in space and time. Yet, several recent studies have indicated that raindrop arrivals are often temporally and spatially correlated. Resolution of this conflict must begin with observations of perfectly uncorrelated rainfall, should such “perfectly steady rain” exist at all. Indeed, it does. Using data with high temporal precision from a two-dimensional video disdrometer and the pair-correlation function, a scale-localized statistical tool, several ∼10–20-min rain episodes have been uncovered where no clustering among droplet arrival times is found. This implies that (i) rain …

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Coherence And Polarization Properties Of Far Fields Generated By Quasi-Homogeneous Planar Electromagnetic Sources, Olga Korotkova, Brian G. Hoover, Victor L. Gamiz, Emil Wolf Nov 2005

Coherence And Polarization Properties Of Far Fields Generated By Quasi-Homogeneous Planar Electromagnetic Sources, Olga Korotkova, Brian G. Hoover, Victor L. Gamiz, Emil Wolf

Physics Articles and Papers

In studies of radiation from partially coherent sources the so-called quasi-homogeneous (QH) model sources have been very useful, for instance in elucidating the behavior of fields produced by thermal sources. The analysis of the fields generated by such sources has, however, been largely carried out in the framework of scalar wave theory. In this paper we generalize the concept of the QH source to the domain of the electromagnetic theory, and we derive expressions for the elements of the cross-spectral density matrix, for the spectral density, the spectral degree of coherence, the degree of polarization, and the Stokes parameters of …

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Entropic Characterization Of Mixing In Microchannels, Marco Camesasca, Ica Manas Zloczower, Miron Kaufman Nov 2005

Entropic Characterization Of Mixing In Microchannels, Marco Camesasca, Ica Manas Zloczower, Miron Kaufman

Physics Faculty Publications

A methodology for rigorous mixing assessment in microchannels is presented. The analysis is based on numerical simulations of flow in different geometries coupled with mixing assessment using entropic measures. The results show enhanced mixing efficiency for the staggered herringbone micromixer by comparison with a mixer with straight diagonal ridges and a lack of mixing in a non-patterned channel. These results are in agreement with published experimental data.

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Evidence For Native-Defect Donors In N-Type Zno, David C. Look, Gary C. Farlow, Pakpoom Reunchan, Sukit Limpijumnong, S. B. Zhang, K. Nordlund Nov 2005

Evidence For Native-Defect Donors In N-Type Zno, David C. Look, Gary C. Farlow, Pakpoom Reunchan, Sukit Limpijumnong, S. B. Zhang, K. Nordlund

Physics Faculty Publications

Recent theory has found that native defects such as the O vacancy VO and Zn interstitial ZnI have high formation energies in n-type ZnO and, thus, are not important donors, especially in comparison to impurities such as H. In contrast, we use both theory and experiment to show that, under N ambient, the complex ZnI-NO is a stronger candidate than H or any other known impurity for a 30 meV donor commonly found in bulk ZnO grown from the vapor phase. Since the Zn vacancy is also the dominant acceptor in such material, we must …

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Spectroscopic And Thermodynamic Characterization Of The E151d And E151a Altered Leucine Aminopeptidases From Aeromonas Proteolytica, Krzysztof P. Bzymek, Sabina I. Swierczek, Brian Bennett, Richard C. Holz Nov 2005

Spectroscopic And Thermodynamic Characterization Of The E151d And E151a Altered Leucine Aminopeptidases From Aeromonas Proteolytica, Krzysztof P. Bzymek, Sabina I. Swierczek, Brian Bennett, Richard C. Holz

Physics Faculty Research and Publications

Previous kinetic characterization of the glutamate 151 (E151)-substituted forms of the leucine aminopeptidase from Aeromonas proteolytica (Vibrio proteolyticus; AAP) has provided critical evidence that this residue functions as the general acid/base. The close proximity of similar glutamate residues to the bridging water/hydroxide of the dinuclear active sites of metalloenzymes (2.80 and 3.94 Å in carboxypeptidase G2 and 3.30 and 3.63 Å in AAP), suggests it may also be involved in stabilizing the active-site metal ions. Therefore, the structural perturbations of the dinuclear active site of AAP were examined for two E151-substituted forms, namely E151D-AAP and E151A-AAP, by …

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Erratum: Publisher's Note: Calculation Of The One- And Two-Loop Lamb Shift For Arbitrary Excited Hydrogenic States (Physical Review Letters (2005) 95 (180404)), Andrzej Czarnecki, Ulrich D. Jentschura, Krzysztof Pachucki Nov 2005

Erratum: Publisher's Note: Calculation Of The One- And Two-Loop Lamb Shift For Arbitrary Excited Hydrogenic States (Physical Review Letters (2005) 95 (180404)), Andrzej Czarnecki, Ulrich D. Jentschura, Krzysztof Pachucki

Physics Faculty Research & Creative Works

No abstract provided.

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Towards A Precision Measurement Of The Casimir Force In A Cylinder-Plane Geometry, M. Brown-Hayes, D. A.R. Dalvit, F. D. Mazzitelli, W. J. Kim, R. Onofrio Nov 2005

Towards A Precision Measurement Of The Casimir Force In A Cylinder-Plane Geometry, M. Brown-Hayes, D. A.R. Dalvit, F. D. Mazzitelli, W. J. Kim, R. Onofrio

Dartmouth Scholarship

We report on a proposal aimed at measuring the Casimir force in the cylinder-plane configuration. The Casimir force is evaluated including corrections due to finite parallelism, conductivity, and temperature. The range of validity of the proximity force approximation is also discussed. An apparatus to test the feasibility of a precision measurement in this configuration has been developed, and we describe both a procedure to control the parallelism and the results of the electrostatic calibration. Finally we discuss the possibility of measuring the thermal contribution to the Casimir force and deviations from the proximity force approximation, both of which are expected …

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Intra-Atomic Aspects Of Magnon-Plasmon Interactions, Ralph Skomski, Peter A. Dowben Nov 2005

Intra-Atomic Aspects Of Magnon-Plasmon Interactions, Ralph Skomski, Peter A. Dowben

Peter Dowben Publications

Magnon-plasmon interactions are modeled by considering the spin-dependent dielectric response of atoms placed in crystalline environment. Hund's exchange rules favor parallel spin alignment, but the strength of the exchange depends on the displacement of the centers of gravity of the atomic spin-up and spin-down electron charge clouds. The intra-atomic exchange is modeled by considering a Hubbard-type interaction, and interatomic interaction then yields a k-space dispersion. The eigenmodes of the plasma are a mixture of spin-up and spin-down degrees of freedom, described by a 2×2 interaction matrix. Minority and majority bands yield different plasmon frequencies. However, these modes are not orthogonal …

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