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Selected Works

2000

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Articles 1 - 21 of 21

Full-Text Articles in Physics

Optically Induced Periodic Structures In Smectic-C Liquid Crystals, Antal Jákli, A. Vajda, E. Benkler, Janossy, Peter Palffy-Muhoray Dec 2000

Optically Induced Periodic Structures In Smectic-C Liquid Crystals, Antal Jákli, A. Vajda, E. Benkler, Janossy, Peter Palffy-Muhoray

Antal Jakli

We explore periodic structures of smectic-C (SmC) liquid crystals, induced optically by a polarization grating. The studied cells contain a passive surface of rubbed polyimide and an active photosensitive substrate of ate-dye doped polyimide. In a nematic phase the director field can be periodic independent of the angle between the grating vector and the rubbing direction. In the SmA phase periodic structure can be induced only by layer undulations. The SmC behaves similarly to the nematic phase, but the director can rotate only on a cone, which results in a more complex geometry. The periodic pattern is superimposed with four ...


Topology And Metastability In The Lattice Skyrme Model, Alec Schramm, Benjamin Svetitsky Nov 2000

Topology And Metastability In The Lattice Skyrme Model, Alec Schramm, Benjamin Svetitsky

Alec J Schramm

We offer the Skyrme model on a lattice as an effective field theory—fully quantized—of baryon-meson interactions at temperatures below the chiral phase transition. We define a local topological density that involves the volumes of tetrahedra in the target space S3 and we make use of Coxeter’s formula for the Schläfli function to implement it. This permits us to calculate the mean-square radius of a Skyrmion in the three-dimensional lattice Skyrme model, which may be viewed as a Ginzburg-Landau effective theory for the full quantum theory at finite temperature. We find that, contrary to expectations, the Skyrmion shrinks ...


Calculating The Tension Of Domain Wall Junctions And Vortices In Generalized Wess-Zumino Models, M Shifman, Tonnis Ter Veldhuis Sep 2000

Calculating The Tension Of Domain Wall Junctions And Vortices In Generalized Wess-Zumino Models, M Shifman, Tonnis Ter Veldhuis

Tonnis ter Veldhuis

No abstract provided.


Relaxation Dynamics Of Rubbed Polystyrene Thin Films, D. M. G. Agra, A. D. Schwab, J-H. Kim, Satyendra Kumar, A. Dhinojwala Aug 2000

Relaxation Dynamics Of Rubbed Polystyrene Thin Films, D. M. G. Agra, A. D. Schwab, J-H. Kim, Satyendra Kumar, A. Dhinojwala

Satyendra Kumar

Optical retardation measurements were used to probe the chain relaxation dynamics in rubbed polystyrene films of varying thicknesses on glass substrates. A model based on Kohlrausch-Williams-Watts relaxation was developed and used to determine the glass transition temperature (Tg) of the films. Results showed reductions of 15–20 K in Tg for thin films of thicknesses comparable to the radius of gyration as well as for cast films rubbed with different strengths. These results provide evidence of a faster relaxation dynamics relative to the polymer-substrate interface for thinner films and enhanced chain mobility at the polymer-air interface.


Measurements Of The Hyperpolarizability Tensor By Means Of Hyper-Rayleigh Scattering, Liang-Chy Chien, V. Ostroverkhova, R. G. Petschek, K. D. Singer, L. Sukhomlinova, R. J. Twieg, S.-X. Wang Aug 2000

Measurements Of The Hyperpolarizability Tensor By Means Of Hyper-Rayleigh Scattering, Liang-Chy Chien, V. Ostroverkhova, R. G. Petschek, K. D. Singer, L. Sukhomlinova, R. J. Twieg, S.-X. Wang

Liang-Chy Chien

We describe improvements to a previously reported hyper-Rayleigh scattering technique [J. Opt. Sec. Am. B 15, 289 (1998)], for measuring all rotational invariants of the first hyperpolarizability tensor. The full hyper-Rayleigh scattering tensor is expressed in terms of its rotationally invariant components leading to a figures of merit corresponding to each of the rotationally invariant tensors. With elliptically polarized incident light, the polarization state and the intensity of the harmonic light are measured at a scattering angle of 45 degrees. A new analytical fitting method is applied to the signal for two polarization measurements to yield the invariants. We have ...


On The Effect Of Long-Wavelength Electron Plasma Waves On Large-Angle Stimulated Raman Scattering Of Short Laser Pulse In Plasmas, Nikolai E. Andreev, Serguei Y. Kalmykov Jul 2000

On The Effect Of Long-Wavelength Electron Plasma Waves On Large-Angle Stimulated Raman Scattering Of Short Laser Pulse In Plasmas, Nikolai E. Andreev, Serguei Y. Kalmykov

Serge Youri Kalmykov

Spectral features of a large-angle stimulated Raman scattering (LA SRS) of a short electromagnetic pulse in an underdense plasma, which are caused by the presence in a plasma of a given linear long-wavelength electron plasma wave (LW EPW), are investigated. It is shown that the LW EPW, whose phase velocity coincides with a group velocity of a pulse and a density perturbation normalized to a background electron density, \delta n_{LW} / n_0, exceeds the ratio of the electron plasma frequency to the laser frequency, \omega_{pe} / \omega_0, suppresses the well-known Stokes branch of the weakly coupled LA SRS. Under the ...


Structure Variation Of Intersubband Electron-Acoustic Phonon Scattering Rate In Coupled Quantum Wells, K Pozela, S.B. Naran, J.P. Leburton, James Heyman Jul 2000

Structure Variation Of Intersubband Electron-Acoustic Phonon Scattering Rate In Coupled Quantum Wells, K Pozela, S.B. Naran, J.P. Leburton, James Heyman

James Heyman

No abstract provided.


Few-Cycle Thz Spectroscopy Of Nanostructures, K Unterrainer, R Kersting, R Bratschitsch, G Strasser, James Heyman, K.D. Maranowski, A.C. Gossard Jun 2000

Few-Cycle Thz Spectroscopy Of Nanostructures, K Unterrainer, R Kersting, R Bratschitsch, G Strasser, James Heyman, K.D. Maranowski, A.C. Gossard

James Heyman

No abstract provided.


Direct And Indirect Limits On The Electro-Magnetic Form Factors Of Wimps, M Pospelov, Tonnis Ter Veldhuis May 2000

Direct And Indirect Limits On The Electro-Magnetic Form Factors Of Wimps, M Pospelov, Tonnis Ter Veldhuis

Tonnis ter Veldhuis

No abstract provided.


The Spectral Function Of A Composite From Reflectance Data., Anthony Day, M. Thorpe, A. Grant, A. Sievers Mar 2000

The Spectral Function Of A Composite From Reflectance Data., Anthony Day, M. Thorpe, A. Grant, A. Sievers

Anthony Roy Day

In the Bergman-Milton spectral representation for the effective dielectric constant of a composite all relevant geometric information is captured in a spectral function that is independent of material properties. We present numerical simulations of the reflectance of a model two component composite, where both components have temperature-dependant dielectric resonances, and show that the spectral function can be extracted from the data. The same spectral function is obtained from simulation data corresponding to different temperatures but the resolution depends on the width of the resonance line and is greatest at low-temperatures.


Domain Wall Junctions In A Generalized Wess-Zumino Model, D Binosi, Tonnis Ter Veldhuis Mar 2000

Domain Wall Junctions In A Generalized Wess-Zumino Model, D Binosi, Tonnis Ter Veldhuis

Tonnis ter Veldhuis

No abstract provided.


Sampling A Terahertz Dipole Transition With Subcycle Time Resolution, R Hersting, R Bratschitsch, G Strassar, K Unterrainer, James Heyman Feb 2000

Sampling A Terahertz Dipole Transition With Subcycle Time Resolution, R Hersting, R Bratschitsch, G Strassar, K Unterrainer, James Heyman

James Heyman

No abstract provided.


Mind-Matter Interaction In Quantum Physics, Milan Meszaros Physicist Feb 2000

Mind-Matter Interaction In Quantum Physics, Milan Meszaros Physicist

Milan Meszaros physicist

By the end of the 20th century, the Einstein-Podolsky-Rosen, Schrödinger’s cat and Wigner’s friend paradoxes of quantum theory were already known. The Bell’s inequalities, the Aharonov-Bohm effect and the holographical principles etc. were also acquainted. There were positive experiments of Aspect, Daligbard and Roger just as Aspect, Grangier and Roger etc. In connection with these paradoxes and paradoxical experiments etc., the questions are raised: What is the ontological frame for description of these effects or notions: nonlocal, guiding wave (pilot wave), instantenous, delayed-choice experiments, superluminal, ghost wave, immaterial or mind, mind-matter interaction, holographical universe or entangled states ...


Spectral Function Of Composites From Reflectivity Measurements, Anthony Day, A. Grant, A. Sievers, M. Thorpe Jan 2000

Spectral Function Of Composites From Reflectivity Measurements, Anthony Day, A. Grant, A. Sievers, M. Thorpe

Anthony Roy Day

We demonstrate a method of calculating the spectral function of a composite from measured reflectivity data. To solve this inverse problem it is necessary for the reflectivity data to be taken through a strong, high Q, resonance. By analyzing the reststrahlen region of different fill fraction KCl-diamond composites at three different temperatures, we find accurate spectral functions that are independent of temperature with the low temperature data giving the best resolution. These spectral functions are then used to successfully predict the optical response of RbCl-diamond composites.


Scalar Absorption By Spinning D3-Branes, George Siopsis Jan 2000

Scalar Absorption By Spinning D3-Branes, George Siopsis

George Siopsis

We discuss absorption of scalars by a distribution of spinning D3-branes. The D3-branes are multi-center solutions of supergravity theory. We solve the wave equation in various cases of supergravity backgrounds in which the equation becomes separable. We show that the absorption coefficients exhibit a universal behavior as functions of the angular momentum quantum number and the Hawking temperature. This behavior is similar to the form of the gray-body factors one encounters in scattering by black holes. Our discussion includes the problematic case of spherically symmetric distributions of D-branes, where resonances arise. We obtain the same universal form for the absorption ...


Evaluating The Effective Action, Br Holstein Dec 1999

Evaluating The Effective Action, Br Holstein

Barry R Holstein

The use of effective field theory, in situations wherein the energy-momentum of light particles is much lower than the rest mass of heavy degrees of freedom, has become an important one in contemporary physics. Herein we examine various means by which this effective action can be evaluated, using the effective photon–photon interaction—the Euler–Heisenberg Lagrangian—as a pedagogical example.


Mirage Mirror On The Wall, T. Kosa, Peter Palffy-Muhoray Dec 1999

Mirage Mirror On The Wall, T. Kosa, Peter Palffy-Muhoray

Peter Palffy-Muhoray

We discuss mirages formed near a sun-heated wall, and consider the underlying physics. The temperature and refractive index variations in air near the wall are estimated, and a simple approximate picture of ray propagation is presented. Estimates of the thermal decay length and ray curvature are compared with experimental observations.


Cluster Monte Carlo Study Of Multicomponent Fluids Of The Stillinger-Helfand And Widom-Rowlinson Type, Rongfeng Sun, Harvey Gould, Jonathan Machta, L. W. Chayes Dec 1999

Cluster Monte Carlo Study Of Multicomponent Fluids Of The Stillinger-Helfand And Widom-Rowlinson Type, Rongfeng Sun, Harvey Gould, Jonathan Machta, L. W. Chayes

Jonathan Machta

Phase transitions of fluid mixtures of the type introduced by Stillinger and Helfand are studied using a continuum version of the invaded cluster algorithm. Particles of the same species do not interact, but particles of different types interact with each other via a repulsive potential. Examples of interactions include the Gaussian molecule potential and a repulsive step potential. Accurate values of the critical density, fugacity, and magnetic exponent are found in two and three dimensions for the two-species model. The effect of varying the number of species and of introducing quenched impurities is also investigated. In all the cases studied ...


Dimension Eight Operators In The Weak Operator Product Expansion, Vincenzo Cirigliano, John Donoghue, Eugene Golowich Dec 1999

Dimension Eight Operators In The Weak Operator Product Expansion, Vincenzo Cirigliano, John Donoghue, Eugene Golowich

John Donoghue

We expose a potential flaw in standard treatments of weak decay amplitudes, including that of epsilon'/epsilon. We show that (contrary to conventional wisdom) dimension-eight operators do contribute to weak amplitudes, at order G_F alpha_s and without 1/M_W^2 suppression. We demonstrate the existence of these operators with a simple weak hamiltonian and proceed to discuss their contribution in a general context. We estimate the effect of dimension-eight operators to be at the 100% level in a sum rule determination of the operator O_7 for mu = 1.5 GeV, suggesting presently available values of mu are too low to ...


Trajectory Mapping: A Tool For Validation Of Trace Gas Observations, Gary A. Morris, James F. Gleason, Jerald Ziemke, Mark R. Schoeberl Dec 1999

Trajectory Mapping: A Tool For Validation Of Trace Gas Observations, Gary A. Morris, James F. Gleason, Jerald Ziemke, Mark R. Schoeberl

Gary A. Morris

We investigate the effectiveness of trajectory mapping(TM) as a data validation tool. TM combines a dynamical model of the atmosphere with trace gas observations to provide more statistically robust estimates of instrument performance over much broader geographic areas than traditional techniques are able to provide. We present four detailed case studies selected so that the traditional techniques are expected to work well. In each case the TM results are equivalent to or improve upon the measurement comparisons performed with traditional approaches. The TM results are statistically more robust than those achieved using traditional approaches since the TM comparisons occur ...


Configurational Entropy And Diffusivity Of Supercooled Water, Francis W. Starr, A. Scala, E. La Nave, F. Sciortino, H. E. Stanley Dec 1999

Configurational Entropy And Diffusivity Of Supercooled Water, Francis W. Starr, A. Scala, E. La Nave, F. Sciortino, H. E. Stanley

Francis Starr

No abstract provided.