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Sample records for plane-wave nonlocal pseudopotential

  1. Complex band structure under plane-wave nonlocal pseudopotential Hamiltonian of metallic wires and electrodes

    SciTech Connect

    Yang, Chao

    2009-07-17

    We present a practical approach to calculate the complex band structure of an electrode for quantum transport calculations. This method is designed for plane wave based Hamiltonian with nonlocal pseudopotentials and the auxiliary periodic boundary condition transport calculation approach. Currently there is no direct method to calculate all the evanescent states for a given energy for systems with nonlocal pseudopotentials. On the other hand, in the auxiliary periodic boundary condition transport calculation, there is no need for all the evanescent states at a given energy. The current method fills this niche. The method has been used to study copper and gold nanowires and bulk electrodes.

  2. Parallel Implementation of Gamma-Point Pseudopotential Plane-Wave DFT with Exact Exchange

    SciTech Connect

    Bylaska, Eric J.; Tsemekhman, Kiril L.; Baden, Scott B.; Weare, John H.; Jonsson, Hannes

    2011-01-15

    One of the more persistent failures of conventional density functional theory (DFT) methods has been their failure to yield localized charge states such as polarons, excitons and solitons in solid-state and extended systems. It has been suggested that conventional DFT functionals, which are not self-interaction free, tend to favor delocalized electronic states since self-interaction creates a Coulomb barrier to charge localization. Pragmatic approaches in which the exchange correlation functionals are augmented with small amount of exact exchange (hybrid-DFT, e.g. B3LYP and PBE0) have shown promise in localizing charge states and predicting accurate band gaps and reaction barriers. We have developed a parallel algorithm for implementing exact exchange into pseudopotential plane-wave density functional theory and we have implemented it in the NWChem program package. The technique developed can readily be employed in plane-wave DFT programs. Furthermore, atomic forces and stresses are straightforward to implement, making it applicable to both confined and extended systems, as well as to Car-Parrinello ab initio molecular dynamic simulations. This method has been applied to several systems for which conventional DFT methods do not work well, including calculations for band gaps in oxides and the electronic structure of a charge trapped state in the Fe(II) containing mica, annite.

  3. Ground- and excited-state properties of DNA base molecules from plane-wave calculations using ultrasoft pseudopotentials.

    PubMed

    Preuss, M; Schmidt, W G; Seino, K; Furthmüller, J; Bechstedt, F

    2004-01-15

    We present equilibrium geometries, vibrational modes, dipole moments, ionization energies, electron affinities, and optical absorption spectra of the DNA base molecules adenine, thymine, guanine, and cytosine calculated from first principles. The comparison of our results with experimental data and results obtained by using quantum chemistry methods show that in specific cases gradient-corrected density-functional theory (DFT-GGA) calculations using ultrasoft pseudopotentials and a plane-wave basis may be a numerically efficient and accurate alternative to methods employing localized orbitals for the expansion of the electron wave functions.

  4. Elastic stability of β-Ti under pressure calculated using a first-principles plane-wave pseudopotential method

    NASA Astrophysics Data System (ADS)

    Hu, Qing-Miao; Lu, Song; Yang, Rui

    2008-08-01

    The elastic moduli c' and c44 of β-Ti with respect to external pressure P (up to about 138 GPa) are calculated with a first-principles plane-wave pseudopotential method. The accuracy of the calculations regarding the plane-wave cut-off energy, k -point mesh, and transferability of the pseudopotentials is carefully tested. It is found that the critical pressure beyond which β-Ti satisfies the elastic stability conditions is about 60 GPa. The Mulliken population analysis shows that both s and p electrons transfer to the d orbitals with increasing pressure, however, the number of s electrons starts to increase when the pressure exceeds about 70 GPa. The number of d electrons at the critical pressure is about 2.96, in perfect agreement with the critical number of d electrons for a stable bcc Ti-V alloy, which demonstrates the correlation between the stability of bcc metals and their d orbital occupation. The bonding charge density calculations show charge accumulation on the d-t2g orbitals under high pressure, which may improve the elastic stability of β-Ti .

  5. Self-interaction corrected LDA + U investigations of BiFeO3 properties: plane-wave pseudopotential method

    NASA Astrophysics Data System (ADS)

    Yaakob, M. K.; Taib, M. F. M.; Lu, L.; Hassan, O. H.; Yahya, M. Z. A.

    2015-11-01

    The structural, electronic, elastic, and optical properties of BiFeO3 were investigated using the first-principles calculation based on the local density approximation plus U (LDA + U) method in the frame of plane-wave pseudopotential density functional theory. The application of self-interaction corrected LDA + U method improved the accuracy of the calculated properties. Results of structural, electronic, elastic, and optical properties of BiFeO3, calculated using the LDA + U method were in good agreement with other calculation and experimental data; the optimized choice of on-site Coulomb repulsion U was 3 eV for the treatment of strong electronic localized Fe 3d electrons. Based on the calculated band structure and density of states, the on-site Coulomb repulsion U had a significant effect on the hybridized O 2p and Fe 3d states at the valence and the conduction band. Moreover, the elastic stiffness tensor, the longitudinal and shear wave velocities, bulk modulus, Poisson’s ratio, and the Debye temperature were calculated for U = 0, 3, and 6 eV. The elastic stiffness tensor, bulk modulus, sound velocities, and Debye temperature of BiFeO3 consistently decreased with the increase of the U value.

  6. First-principles calculation of spectral features, chemical shift and absolute threshold of ELNES and XANES using a plane wave pseudopotential method

    NASA Astrophysics Data System (ADS)

    Mizoguchi, Teruyasu; Tanaka, Isao; Gao, Shang-Peng; Pickard, Chris J.

    2009-03-01

    Spectral features, chemical shifts, and absolute thresholds of electron energy loss near-edge structure (ELNES) and x-ray absorption near-edge structure (XANES) for selected compounds, i.e. TiO2 (rutile), TiO2 (anatase), SrTiO3, Ti2O3, Al2O3, AlN and β-Ga2O3, were calculated by a plane wave pseudopotential method. Experimental ELNES/XANES of those compounds were well reproduced when an excited pseudopotential, which includes a core hole, was used. In addition to the spectral features, it was found that chemical shifts among different compounds were also reproduced by correcting the contribution of the excited pseudopotentials to the energy of the core orbital.

  7. Study on the maximum accuracy of the pseudopotential density functional method with localized atomic orbitals versus plane-wave basis sets.

    PubMed

    Gusso, Michele

    2008-01-28

    A detailed study on the accuracy attainable with numerical atomic orbitals in the context of pseudopotential first-principles density functional theory is presented. Dimers of first- and second-row elements are analyzed: bond lengths, atomization energies, and Kohn-Sham eigenvalue spectra obtained with localized orbitals and with plane-wave basis sets are compared. For each dimer, the cutoff radius, the shape, and the number of the atomic basis orbitals are varied in order to maximize the accuracy of the calculations. Optimized atomic orbitals are obtained following two routes: (i) maximization of the projection of plane wave results into atomic orbital basis sets and (ii) minimization of the total energy with respect to a set of primitive atomic orbitals as implemented in the OPENMX software package. It is found that by optimizing the numerical basis, chemical accuracy can be obtained even with a small set of orbitals.

  8. Cytochrome P450 compound I in the plane wave pseudopotential framework: GGA electronic and geometric structure of thiolate-ligated iron(IV)-oxo porphyrin.

    PubMed

    Elenewski, Justin E; Hackett, John C

    2013-07-15

    The cytochromes P450 constitute a ubiquitous family of metalloenzymes, catalyzing manifold reactions of biological and synthetic importance via a thiolate-ligated iron-oxo (IV) porphyrin radical species denoted compound I (Cpd I). Experimental investigations have implicated this intermediate in a broad spectrum of biophysically interesting phenomena, further augmenting the importance of a Cpd I model system. Ab initio molecular dynamics, including Car-Parrinello and path integral methods, conjoin electronic structure theory with finite temperature simulation, affording tools most valuable to approach such enzymes. These methods are typically driven by density functional theory (DFT) in a plane-wave pseudopotential framework; however, existing studies of Cpd I have been restricted to localized Gaussian basis sets. The appropriate choice of density functional and pseudopotential for such simulations is accordingly not obvious. To remedy this situation, a systematic benchmarking of thiolate-ligated Cpd I is performed using several generalized-gradient approximation (GGA) functionals in the Martins-Troullier and Vanderbilt ultrasoft pseudopotential schemes. The resultant electronic and structural parameters are compared to localized-basis DFT calculations using GGA and hybrid density functionals. The merits and demerits of each scheme are presented in the context of reproducing existing experimental and theoretical results for Cpd I.

  9. Cytochrome P450 compound I in the plane wave pseudopotential framework: GGA electronic and geometric structure of thiolate-ligated iron(IV)-oxo porphyrin.

    PubMed

    Elenewski, Justin E; Hackett, John C

    2013-07-15

    The cytochromes P450 constitute a ubiquitous family of metalloenzymes, catalyzing manifold reactions of biological and synthetic importance via a thiolate-ligated iron-oxo (IV) porphyrin radical species denoted compound I (Cpd I). Experimental investigations have implicated this intermediate in a broad spectrum of biophysically interesting phenomena, further augmenting the importance of a Cpd I model system. Ab initio molecular dynamics, including Car-Parrinello and path integral methods, conjoin electronic structure theory with finite temperature simulation, affording tools most valuable to approach such enzymes. These methods are typically driven by density functional theory (DFT) in a plane-wave pseudopotential framework; however, existing studies of Cpd I have been restricted to localized Gaussian basis sets. The appropriate choice of density functional and pseudopotential for such simulations is accordingly not obvious. To remedy this situation, a systematic benchmarking of thiolate-ligated Cpd I is performed using several generalized-gradient approximation (GGA) functionals in the Martins-Troullier and Vanderbilt ultrasoft pseudopotential schemes. The resultant electronic and structural parameters are compared to localized-basis DFT calculations using GGA and hybrid density functionals. The merits and demerits of each scheme are presented in the context of reproducing existing experimental and theoretical results for Cpd I. PMID:23670855

  10. Nonlocal Symmetry of the Lax Equation Related to Riccati-Type Pseudopotential

    NASA Astrophysics Data System (ADS)

    Wang, Yun-Hu; Chen, Yong; Xin, Xiang-Peng

    2012-12-01

    We investigate the Lax equation that can be employed to describe motions of long waves in shallow water under gravity. A nonlocal symmetry of this equation is given and used to find exact solutions and derive lower integrable models from higher ones. It is interesting that this nonlocal symmetry links with its corresponding Riccati-type pseudopotential. By introducing suitable and simple auxiliary dependent variables, the nonlocal symmetry is localized and used to generate new solutions from trivial solutions. Meanwhile, this equation is reduced to an ordinary differential equation by means of this nonlocal symmetry and some local symmetries.

  11. Ab initio simulation of photoemission spectroscopy in solids: Plane-wave pseudopotential approach with applications to normal-emission spectra of Cu(001) and Cu(111)

    NASA Astrophysics Data System (ADS)

    Stojić, Nataša; Dal Corso, Andrea; Zhou, Bo; Baroni, Stefano

    2008-05-01

    We develop a method for simulating photoemission spectra from bulk crystals in the ultraviolet energy range within a three-step model. Our method explicitly accounts for transmission and matrix-element effects, as calculated from state-of-the-art plane-wave pseudopotential techniques within the density-functional theory. Transmission effects, in particular, are included by extending to the present problem a technique previously employed with success to deal with ballistic conductance in metal nanowires. The spectra calculated for normal emission in Cu(001) and Cu(111) are in fair agreement with previous theoretical results and with experiments, including a recently determined experimental spectrum. The residual discrepancies between our results and the latter are mainly due to the well-known deficiencies of the density-functional theory in accounting for correlation effects in quasiparticle spectra. A significant improvement is obtained by the LDA+U method. Further improvements are obtained by including surface-optics corrections, as described by Snell’s law and Fresnel’s equations.

  12. Plane wave scattering from a plasmonic nanowire-film system with the inclusion of non-local effects.

    PubMed

    Trivedi, Rahul; Sharma, Yashna; Dhawan, Anuj

    2015-10-01

    In this paper we present a theoretical analysis of the electromagnetic response of a plasmonic nanowire-film system. The analytical solution accounts for both the dispersive as well as non-local nature of the plasmonic media. The physical structure comprises of a plasmonic nanowire made of a plasmonic metal such as gold or silver placed over a plasmonic film of the same material. Such a nanostructure exhibits a spectrum that is extremely sensitive to various geometric parameters such as spacer thickness and nanowire radius, which makes it favorable for various sensing applications. The non-locality of the plasmonic medium, which can be captured using the hydrodynamic model, significantly affects the resonant wavelength of this system for structures of small dimensions (~ less than 5 nm gap between the nanowire and the film). We present an analytical method that can be used to predict the effect of non-locality on the resonances of the system. To validate the analytical method, we also report a comparison of our analytical solution with a numerical Finite Difference Time Domain analysis (FDTD) of the same structure with the plasmonic medium being treated as local in nature.

  13. Plane wave scattering from a plasmonic nanowire-film system with the inclusion of non-local effects.

    PubMed

    Trivedi, Rahul; Sharma, Yashna; Dhawan, Anuj

    2015-10-01

    In this paper we present a theoretical analysis of the electromagnetic response of a plasmonic nanowire-film system. The analytical solution accounts for both the dispersive as well as non-local nature of the plasmonic media. The physical structure comprises of a plasmonic nanowire made of a plasmonic metal such as gold or silver placed over a plasmonic film of the same material. Such a nanostructure exhibits a spectrum that is extremely sensitive to various geometric parameters such as spacer thickness and nanowire radius, which makes it favorable for various sensing applications. The non-locality of the plasmonic medium, which can be captured using the hydrodynamic model, significantly affects the resonant wavelength of this system for structures of small dimensions (~ less than 5 nm gap between the nanowire and the film). We present an analytical method that can be used to predict the effect of non-locality on the resonances of the system. To validate the analytical method, we also report a comparison of our analytical solution with a numerical Finite Difference Time Domain analysis (FDTD) of the same structure with the plasmonic medium being treated as local in nature. PMID:26480121

  14. Nonlocal Pseudopotentials and Long-Range Interactions in Ab Initio Finite-Element Electronic-Structure Calculations

    NASA Astrophysics Data System (ADS)

    Pask, J. E.; Sterne, P. A.

    2004-03-01

    The finite-element (FE) method is a general approach for the solution of partial differential equations. Like the planewave (PW) method, the FE method is a systematically improvable expansion approach. Unlike the PW method, however, its basis functions are strictly local in real space, which allows for variable resolution in real space and facilitates massively parallel implementation. We discuss the application of the FE method to ab initio electronic-structure calculations.(J.E. Pask, B.M. Klein, C.Y. Fong, and P.A. Sterne, Phys. Rev. B 59), 12352 (1999). In particular, we discuss the use of nonlocal pseudopotentials in bulk calculations, and the handling of long-range interactions in the construction of the Kohn-Sham effective potential and total energy. We show that the total energy converges variationally, and at the optimal theoretical rate consistent with the cubic completeness of the basis. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

  15. Plane-wave DFT-LDA calculation of the electronic structure and absorption spectrum of copper

    NASA Astrophysics Data System (ADS)

    Marini, Andrea; Onida, Giovanni; del Sole, Rodolfo

    2001-11-01

    We present an accurate, first-principles study of the electronic structure and absorption spectrum of bulk copper within density functional theory in the local density approximation, including the study of intraband transitions. We construct norm-conserving pseudopotentials (PP's) including the 3d shell (and optionally the underlying 3s and 3p shells) in the valence and requiring a relatively small plane-wave basis (60 and 140 Ry cutoff, respectively). As a consequence, these PP's are strongly nonlocal, yielding macroscopically wrong results in the absorption spectrum when momentum matrix elements are computed naively. Our results are compared with experimental photoemission, absorption, and electron energy loss data, and suggest nontrivial self-energy effects in the quasiparticle spectrum of Cu.

  16. Plane waves as tractor beams

    NASA Astrophysics Data System (ADS)

    Forgács, Péter; Lukács, Árpád; Romańczukiewicz, Tomasz

    2013-12-01

    It is shown that in a large class of systems, plane waves act as tractor beams: i.e., an incident plane wave can exert a pulling force on the scatterer. The underlying physical mechanism for the pulling force is due to the sufficiently strong scattering of the incoming wave into another mode carrying more momentum, in which case excess momentum is created behind the scatterer. This tractor beam or negative radiation pressure (NRP) effect, is found to be generic in systems with multiple scattering channels. In a birefringent medium, electromagnetic plane waves incident on a thin plate exert NRP of the same order of magnitude as optical radiation pressure, while in artificial dielectrics (metamaterials), the magnitude of NRP can even be macroscopic. In two dimensions, we study various scattering situations on vortices, and NRP is shown to occur by the scattering of heavy baryons into light leptons off cosmic strings, and by neutron scattering off vortices in the XY model.

  17. Plane waves in noncommutative fluids

    NASA Astrophysics Data System (ADS)

    Abdalla, M. C. B.; Holender, L.; Santos, M. A.; Vancea, I. V.

    2013-08-01

    We study the dynamics of the noncommutative fluid in the Snyder space perturbatively at the first order in powers of the noncommutative parameter. The linearized noncommutative fluid dynamics is described by a system of coupled linear partial differential equations in which the variables are the fluid density and the fluid potentials. We show that these equations admit a set of solutions that are monochromatic plane waves for the fluid density and two of the potentials and a linear function for the third potential. The energy-momentum tensor of the plane waves is calculated.

  18. Optimization Algorithm for the Generation of ONCV Pseudopotentials

    NASA Astrophysics Data System (ADS)

    Schlipf, Martin; Gygi, Francois

    2015-03-01

    We present an optimization algorithm to construct pseudopotentials and use it to generate a set of Optimized Norm-Conserving Vanderbilt (ONCV) pseudopotentials for elements up to Z=83 (Bi) (excluding Lanthanides). We introduce a quality function that assesses the agreement of a pseudopotential calculation with all-electron FLAPW results, and the necessary plane-wave energy cutoff. This quality function allows us to use a Nelder-Mead optimization algorithm on a training set of materials to optimize the input parameters of the pseudopotential construction for most of the periodic table. We control the accuracy of the resulting pseudopotentials on a test set of materials independent of the training set. We find that the automatically constructed pseudopotentials provide a good agreement with the all-electron results obtained using the FLEUR code with a plane-wave energy cutoff of approximately 60 Ry. Supported by DOE/BES Grant DE-SC0008938.

  19. Explosive plane-wave lens

    DOEpatents

    Marsh, S.P.

    1988-03-08

    An explosive plane-wave air lens which enables a spherical wave form to be converted to a planar wave without the need to specially machine or shape explosive materials is described. A disc-shaped impactor having a greater thickness at its center than around its periphery is used to convert the spherical wave into a plane wave. When the wave reaches the impactor, the center of the impactor moves first because the spherical wave reaches the center of the impactor first. The wave strikes the impactor later in time as one moves radially along the impactor. Because the impactor is thinner as one moves radially outward, the velocity of the impactor is greater at the periphery than at the center. An acceptor explosive is positioned so that the impactor strikes the acceptor simultaneously. Consequently, a plane detonation wave is propagated through the acceptor explosive. 4 figs.

  20. Explosive plane-wave lens

    DOEpatents

    Marsh, Stanley P.

    1988-01-01

    An explosive plane-wave air lens which enables a spherical wave form to be converted to a planar wave without the need to specially machine or shape explosive materials is described. A disc-shaped impactor having a greater thickness at its center than around its periphery is used to convert the spherical wave into a plane wave. When the wave reaches the impactor, the center of the impactor moves first because the spherical wave reaches the center of the impactor first. The wave strikes the impactor later in time as one moves radially along the impactor. Because the impactor is thinner as one moves radially outward, the velocity of the impactor is greater at the periphery than at the center. An acceptor explosive is positioned so that the impactor strikes the acceptor simultaneously. Consequently, a plane detonation wave is propagated through the acceptor explosive.

  1. Explosive plane-wave lens

    DOEpatents

    Marsh, S.P.

    1987-03-12

    An explosive plane-wave air lens which enables a spherical wave form to be converted to a planar wave without the need to specially machine or shape explosive materials is described. A disc-shaped impactor having a greater thickness at its center than around its periphery is used to convert the spherical wave into a plane wave. When the wave reaches the impactor, the center of the impactor moves first because the spherical wave reaches the center of the impactor first. The wave strikes the impactor later in time as one moves radially along the impactor. Because the impactor is thinner as one moves radially outward, the velocity of the impactor is greater at the periphery than at the center. An acceptor explosive is positioned so that the impactor strikes the acceptor simultaneously. Consequently, a plane detonation wave is propagated through the acceptor explosive. 3 figs., 3 tabs.

  2. Harmonic plane wave propagation in gyroelectric media

    NASA Astrophysics Data System (ADS)

    Hillion, Pierre

    2006-05-01

    We analyse the behaviour of harmonic plane waves in unbounded gyroelectric media once the refractive index in the direction of propagation is known from the Fresnel equation. We get, for the electric and magnetic fields, analytical expressions simple enough to use in a plane wave spectrum representation of more structured electromagnetic fields in these media. We also discuss the reflection and refraction of harmonic plane waves at the boundary between an isotropic medium and a gyroelectric material.

  3. Optimization algorithm for the generation of ONCV pseudopotentials

    NASA Astrophysics Data System (ADS)

    Schlipf, Martin; Gygi, François

    2015-11-01

    We present an optimization algorithm to construct pseudopotentials and use it to generate a set of Optimized Norm-Conserving Vanderbilt (ONCV) pseudopotentials for elements up to Z = 83 (Bi) (excluding Lanthanides). We introduce a quality function that assesses the agreement of a pseudopotential calculation with all-electron FLAPW results, and the necessary plane-wave energy cutoff. This quality function allows us to use a Nelder-Mead optimization algorithm on a training set of materials to optimize the input parameters of the pseudopotential construction for most of the periodic table. We control the accuracy of the resulting pseudopotentials on a test set of materials independent of the training set. We find that the automatically constructed pseudopotentials

  4. Plane wave spectrum of electromagnetic beams

    NASA Astrophysics Data System (ADS)

    Doicu, A.; Wriedt, T.

    1997-02-01

    A plane wave spectrum method of Gaussian beams can be derived by using Davis' approximations for the vector potential. An equivalent vector potential is introduced by considering the inverse Fourier transform of the spectrum function of the original vector potential in a given plane. The electromagnetic field, which corresponds to the equivalent vector potential, satisfies Maxwell's equations and can be written as a sum of plane waves. The beam shape coefficients, or the expansion coefficients in terms of regular spherical vector wave functions, are expressed as simple integrals. This version of the plane wave spectrum method offers the possibility to compute higher-order corrections for Gaussian beams.

  5. Double plane wave reverse time migration with plane wave Green's function

    NASA Astrophysics Data System (ADS)

    Zhao, Z.; Sen, M. K.; Stoffa, P. L.

    2015-12-01

    Reverse time migration (RTM) is effective in obtaining complex subsurface structures from seismic data. By solving the two-way wave equation, RTM can use entire wavefield for imaging. Although powerful computer are becoming available, the conventional pre-stack shot gather RTM is still computationally expensive. Solving forward and backward wavefield propagation for each source location and shot gather is extremely time consuming, especially for large seismic datasets. We present an efficient, accurate and flexible plane wave RTM in the frequency domain where we utilize a compressed plane wave dataset, known as the double plane wave (DPW) dataset. Provided with densely sampled seismic dataset, shot gathers can be decomposed into source and receiver plane wave components with minimal artifacts. The DPW RTM is derived under the Born approximation and utilizes frequency domain plane wave Green's function for imaging. Time dips in the shot profiles can help to estimate the range of plane wave components present in shot gathers. Therefore, a limited number of plane wave Green's functions are needed for imaging. Plane wave Green's functions can be used for imaging both source and receiver plane waves. Source and receiver reciprocity can be used for imaging plane wave components at no cost and save half of the computation time. As a result, the computational burden for migration is substantially reduced. Plane wave components can be migrated independently to recover specific targets with given dips, and ray parameter common image gathers (CIGs) can be generated after migration directly. The ray parameter CIGs can be used to justify the correctness of velocity models. Subsurface anisotropy effects can also be included in our imaging condition, provided with plane wave Green's functions in the anisotropic media.

  6. Horizons and plane waves: A review

    SciTech Connect

    Hubeny, Veronika E.; Rangamani, Mukund

    2003-11-06

    We review the attempts to construct black hole/string solutions in asymptotically plane wave spacetimes. First, we demonstrate that geometries admitting a covariantly constant null Killing vector cannot admit event horizons, which implies that pp-waves can't describe black holes. However, relaxing the symmetry requirements allows us to generate solutions which do possess regular event horizons while retaining the requisite asymptotic properties. In particular, we present two solution generating techniques and use them to construct asymptotically plane wave black string/brane geometries.

  7. Simple Harmonic Motion in Harmonic Plane Waves.

    ERIC Educational Resources Information Center

    Benumof, Reuben

    1980-01-01

    Discusses the distribution of kinetic and potential energy in transverse and longitudinal waves and examines the transmission of power and momentum. This discussion is intended to aid in understanding the simple harmonic motion of a particle involved in the propagation of a harmonic mechanical plane wave. (HM)

  8. NEXAFS spectra of aromatic molecules by plane-wave calculations

    NASA Astrophysics Data System (ADS)

    Fratesi, Guido; Brivio, Gian Paolo

    2013-03-01

    Near-edge x-ray absorption fine structure (NEXAFS) is a powerful technique which allows one to determine several important properties of organic molecules, both in the gas phase and in the bulk or adsorbed one and especially, by performing angle-dependent measurements with polarized x-rays, to the absolute orientation of molecules. This calls for the association of measured peaks to specific transitions, which can be guided by theory. To this respect, the use of numerically-efficient yet accurate first-principles simulations in determining the spectral features is desirable, aiming at simulating fairly large systems such as molecules interacting with metal/dielectric surfaces. We consider here a technique from the literature to derive effectively the spectrum from density-functional theory, using pseudopotentials and plane wave basis sets, that was mostly applied to bulk systems. The basic aspects to its applicability to molecular systems will be discussed, taking as examples benzene, pentacene, and related molecules and comparing to experimental and theoretical data in the literature with special emphasis on the spectrum dependence on the photon polarization.

  9. Strings in plane wave backgrounds reexamined

    SciTech Connect

    Jofre, O.; Nunez, C. Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires )

    1994-10-15

    String theory in an exact plane wave background is explored. The four-tachyon scattering amplitude is constructed. The spectrum of states found from the poles in the factorization turns out to be equivalent to that of the theory in flat space-time. The massless vertex operator is obtained from the residue of the first order pole. It exhibits nontrivial modifications with respect to the flat space case.

  10. Basis set effects on frontier molecular orbital energies and energy gaps: a comparative study between plane waves and localized basis functions in molecular systems.

    PubMed

    Matus, Myrna H; Garza, Jorge; Galván, Marcelo

    2004-06-01

    In order to study the Kohn-Sham frontier molecular orbital energies in the complete basis limit, a comparative study between localized functions and plane waves, obtained with the local density approximation exchange-correlation functional is made. The analyzed systems are ethylene and butadiene, since they are theoretical and experimentally well characterized. The localized basis sets used are those developed by Dunning. For the plane-waves method, the pseudopotential approximation is employed. The results obtained by the localized basis sets suggest that it is possible to get an estimation of the orbital energies in the limit of the complete basis set, when the basis set size is large. It is shown that the frontier molecular orbital energies and the energy gaps obtained with plane waves are similar to those obtained with a large localized basis set, when the size of the supercell and the plane-wave expansion have been appropriately calibrated.

  11. Blackfolds, plane waves and minimal surfaces

    NASA Astrophysics Data System (ADS)

    Armas, Jay; Blau, Matthias

    2015-07-01

    Minimal surfaces in Euclidean space provide examples of possible non-compact horizon geometries and topologies in asymptotically flat space-time. On the other hand, the existence of limiting surfaces in the space-time provides a simple mechanism for making these configurations compact. Limiting surfaces appear naturally in a given space-time by making minimal surfaces rotate but they are also inherent to plane wave or de Sitter space-times in which case minimal surfaces can be static and compact. We use the blackfold approach in order to scan for possible black hole horizon geometries and topologies in asymptotically flat, plane wave and de Sitter space-times. In the process we uncover several new configurations, such as black helicoids and catenoids, some of which have an asymptotically flat counterpart. In particular, we find that the ultraspinning regime of singly-spinning Myers-Perry black holes, described in terms of the simplest minimal surface (the plane), can be obtained as a limit of a black helicoid, suggesting that these two families of black holes are connected. We also show that minimal surfaces embedded in spheres rather than Euclidean space can be used to construct static compact horizons in asymptotically de Sitter space-times.

  12. Polarization of almost-plane waves.

    PubMed

    Sheppard, C J

    2000-02-01

    The general polarization behavior of almost-plane waves, in which the electric field varies slowly over a circular pupil, is considered, on the basis of an axial Hertz potential treatment and expansion in Zernike polynomials. The resultant modes of a circular aperture are compared with the well-known waveguide (or optical fiber) modes and Gaussian beam modes. The wave can be decomposed into partial waves of electric and magnetic types. The modes for a square pupil are also considered. The particular application of the effect on polarization of focusing the waves is discussed. Another application discussed is the Fresnel reflection from a dielectric interface, it being shown that the Fresnel reflection alters the relative strength of the electric and magnetic components.

  13. Plane wave gravitons, curvature singularities and string physics

    SciTech Connect

    Brooks, R. . Center for Theoretical Physics)

    1991-03-21

    This paper discusses bounded (compactifying) potentials arising from a conspiracy between plane wave graviton and dilaton condensates. So are string propagation and supersymmetry in spacetimes with curvature singularities.

  14. Open strings in the plane wave background II: superalgebras and spectra

    NASA Astrophysics Data System (ADS)

    Skenderis, Kostas; Taylor, Marika

    2003-07-01

    In hep-th/0211011 we started a systematic investigation of open strings in the plane wave background. In this paper we continue the analysis by discussing the superalgebras of conserved charges, the spectra of open strings, and the spectra of DBI fluctuations around D-brane embeddings. We also derive the gluing conditions for corresponding boundary states and analyze their symmetries. All results are consistent with each other, and confirm the existence of additional supersymmetries as previously discussed. We further show that for every symmetry current one can construct a (countably) infinite number of related currents that contain more worldsheet derivatives, and discuss non-local symmetries.

  15. Pseudopotentials for quantum Monte Carlo studies of transition metal oxides

    DOE PAGES

    Krogel, Jaron T.; Santana Palacio, Juan A.; Reboredo, Fernando A.

    2016-02-22

    Quantum Monte Carlo (QMC) calculations of transition metal oxides are partially limited by the availability of high-quality pseudopotentials that are both accurate in QMC and compatible with major plane-wave electronic structure codes. We have generated a set of neon-core pseudopotentials with small cutoff radii for the early transition metal elements Sc to Zn within the local density approximation of density functional theory. The pseudopotentials have been directly tested for accuracy within QMC by calculating the first through fourth ionization potentials of the isolated transition metal (M) atoms and the binding curve of each M-O dimer. We find the ionization potentialsmore » to be accurate to 0.16(1) eV, on average, relative to experiment. The equilibrium bond lengths of the dimers are within 0.5(1)% of experimental values, on average, and the binding energies are also typically accurate to 0.18(3) eV. The level of accuracy we find for atoms and dimers is comparable to what has recently been observed for bulk metals and oxides using the same pseudopotentials. Our QMC pseudopotential results compare well with the findings of previous QMC studies and benchmark quantum chemical calculations.« less

  16. Pseudopotentials for quantum Monte Carlo studies of transition metal oxides

    NASA Astrophysics Data System (ADS)

    Krogel, Jaron T.; Santana, Juan A.; Reboredo, Fernando A.

    2016-02-01

    Quantum Monte Carlo (QMC) calculations of transition metal oxides are partially limited by the availability of high-quality pseudopotentials that are both accurate in QMC and compatible with major plane-wave electronic structure codes. We have generated a set of neon-core pseudopotentials with small cutoff radii for the early transition metal elements Sc to Zn within the local density approximation of density functional theory. The pseudopotentials have been directly tested for accuracy within QMC by calculating the first through fourth ionization potentials of the isolated transition metal (M) atoms and the binding curve of each M-O dimer. We find the ionization potentials to be accurate to 0.16(1) eV, on average, relative to experiment. The equilibrium bond lengths of the dimers are within 0.5(1)% of experimental values, on average, and the binding energies are also typically accurate to 0.18(3) eV. The level of accuracy we find for atoms and dimers is comparable to what has recently been observed for bulk metals and oxides using the same pseudopotentials. Our QMC pseudopotential results also compare well with the findings of previous QMC studies and benchmark quantum chemical calculations.

  17. Pseudopotential Computations for Metal/Alumina Interfaces

    NASA Astrophysics Data System (ADS)

    Zhang, Wenqing

    2003-03-01

    Metal/alumina interfaces are found, for example, in electronic devices, as thermal barrier coatings in gas turbines, and in coatings to inhibit corrosion and wear. Of particular importance to their performance is their adhesion. Ultrasoft pseudopotentials combined with plane wave methods and density-functional theory have been employed to compute the properties of these relatively complex interfaces, including effects of impurity segregation. Interfacial stoichiometry and impurity content affect interfacial properties importantly. Thermodynamic links between our first principles results and metallurgical variables such as oxygen activity and oxygen partial pressure are established. This allows for a comparison between theoretical predictions and experimental measurements. Good agreement is obtained for predicted interfacial variables such as atomic structure and adhesive bond strengths on comparison with results of sessile drop, fracture, and other experiments on interfaces of Ni, Cu, Al, and Ag with alumina [1-3], including effects of water and sulfur interfacial impurities. Understanding of the nature of the adhesive bonding at the atomic level is obtained by the pseudopotential first principles approach. [1] W.Zhang, and J.R.Smith, and A.G.Evans, Acta Mater., 50,3803(2002). [2] W.Zhang, and J.R.Smith, Phys. Rev. Lett. 85, 3225(2000). [3] W.Zhang, and J.R.Smith, Phys. Rev. B61, 16883(2000).

  18. Fast plane wave density functional theory molecular dynamics calculations on multi-GPU machines

    SciTech Connect

    Jia, Weile; Fu, Jiyun; Cao, Zongyan; Wang, Long; Chi, Xuebin; Gao, Weiguo; Wang, Lin-Wang

    2013-10-15

    Plane wave pseudopotential (PWP) density functional theory (DFT) calculation is the most widely used method for material simulations, but its absolute speed stagnated due to the inability to use large scale CPU based computers. By a drastic redesign of the algorithm, and moving all the major computation parts into GPU, we have reached a speed of 12 s per molecular dynamics (MD) step for a 512 atom system using 256 GPU cards. This is about 20 times faster than the CPU version of the code regardless of the number of CPU cores used. Our tests and analysis on different GPU platforms and configurations shed lights on the optimal GPU deployments for PWP-DFT calculations. An 1800 step MD simulation is used to study the liquid phase properties of GaInP.

  19. Plane wave density functional theory studies of the structural and the electronic properties of amino acids attached to graphene oxide via peptide bonding

    NASA Astrophysics Data System (ADS)

    Min, Byeong June; Jeong, Hae Kyung; Lee, ChangWoo

    2015-08-01

    We studied via plane wave pseudopotential total-energy calculations within the local spin density approximation (LSDA) the electronic and the structural properties of amino acids (alanine, glycine, and histidine) attached to graphene oxide (GO) by peptide bonding. The HOMO-LUMO gap, the Hirshfeld charges, and the equilibrium geometrical structures exhibit distinctive variations that depend on the species of the attached amino acid. The GO-amino acid system appears to be a good candidate for a biosensor.

  20. Pseudopotential study of barium chalcogenides under hydrostatic pressure

    NASA Astrophysics Data System (ADS)

    Benamrani, A.; Kassali, K.; Bouamama, Kh.

    2010-03-01

    We present first-principles calculations within the pseudo-potential plane wave method in the local density approximation (LDA) and the generalised gradient approximation so as to study the structural properties of BaX (X=S, Se and Te) in both NaCl and CsCl structures. The elastic, vibrational properties and lattice dynamics are calculated with the LDA and the density functional perturbation theory. The pressure dependence of the structural, vibrational and lattice dynamics has been investigated by varying the volume. A good agreement is obtained between our calculation and the available experimental and theoretical data.

  1. Colliding plane waves in F(R)=RN gravity

    NASA Astrophysics Data System (ADS)

    Tahamtan, T.; Halilsoy, M.; Habib Mazharimousavi, S.

    2016-10-01

    We identify a region of a specific F( R)= R N gravity solution without external sources which is isometric to the spacetime of colliding plane waves (CPW). The analogy renders construction and collision of plane waves in F( R)= R N gravity possible. The geometry of the interaction region is equivalent to the Reissner-Nordström (RN) one, however there is no Einstein-Maxwell (EM) source --this is made possible by using the model of RN gravity and the parameter N>1 creates the source. For N=1, we naturally recover the plane waves (and their collision) in Einstein's theory.

  2. Plane-wave decomposition of spatially random fields.

    PubMed

    Nguyen, Tan H; Majeed, Hassaan; Popescu, Gabriel

    2015-04-01

    We investigate the uniqueness of the plane-wave decomposition of temporally deterministic, spatially random fields. Specifically, we consider the decomposition of spatially ergodic and, thus, statistically homogeneous fields. We show that when the spatial power spectrum is injective, the plane waves are the only possible coherent modes. Furthermore, the randomness of such fields originates in the spatial spectral phase, i.e., the phase associated with the coefficients of each plane wave in the expansion. By contrast, the spectral amplitude is deterministic and is specified by the spatial power spectrum. We end with a discussion showing how the results can be translated in full to the time domain.

  3. DLCQ and plane wave matrix Big Bang models

    NASA Astrophysics Data System (ADS)

    Blau, Matthias; O'Loughlin, Martin

    2008-09-01

    We study the generalisations of the Craps-Sethi-Verlinde matrix big bang model to curved, in particular plane wave, space-times, beginning with a careful discussion of the DLCQ procedure. Singular homogeneous plane waves are ideal toy-models of realistic space-time singularities since they have been shown to arise universally as their Penrose limits, and we emphasise the role played by the symmetries of these plane waves in implementing the flat space Seiberg-Sen DLCQ prescription for these curved backgrounds. We then analyse various aspects of the resulting matrix string Yang-Mills theories, such as the relation between strong coupling space-time singularities and world-sheet tachyonic mass terms. In order to have concrete examples at hand, in an appendix we determine and analyse the IIA singular homogeneous plane wave - null dilaton backgrounds.

  4. X-ray absorption spectra of water within a plane-wave Car-Parrinello molecular dynamics framework

    NASA Astrophysics Data System (ADS)

    Cavalleri, Matteo; Odelius, Michael; Nilsson, Anders; Pettersson, Lars G. M.

    2004-11-01

    We describe the implementation of a simple technique to simulate core-level spectra within the Car-Parrinello plane-waves molecular dynamics framework. The x-ray absorption (XA) spectra are generated using the transition potential technique with the effect of the core hole included through a specifically developed pseudopotential for the core-excited atom. Despite the lack of 1s core orbitals in the pseudopotential treatment, the required transition moments are accurately calculated without reconstruction of the all-electron orbitals. The method is applied to the oxygen XA spectra of water in its various aggregation states, but it is transferable to any first-row element. The computed spectra are compared favorably with the results from all-electron cluster calculations, as well as with experimental data. The periodicity of the plane-wave technique improves the description of condensed phases. The molecular dynamics simulation enables in principle a proper treatment of thermal effects and dynamical averaging in complex systems.

  5. The Plane-Wave/Super Yang-Mills Duality

    SciTech Connect

    Sadri, D

    2003-10-14

    We present a self-contained review of the Plane-wave/super-Yang-Mills duality, which states that strings on a plane-wave background are dual to a particular large R-charge sector of N=4, D=4 superconformal U(N) gauge theory. This duality is a specification of the usual AdS/CFT correspondence in the ''Penrose limit''. The Penrose limit of AdS{sub 5} S{sup 5} leads to the maximally supersymmetric ten dimensional plane-wave (henceforth the plane-wave) and corresponds to restricting to the large R-charge sector, the BMN sector, of the dual superconformal field theory. After assembling the necessary background knowledge, we state the duality and review some of its supporting evidence. We review the suggestion by 't Hooft that Yang-Mills theories with gauge groups of large rank might be dual to string theories and the realization of this conjecture in the form of the AdS/CFT duality. We discuss plane-waves as exact solutions of supergravity and their appearance as Penrose limits of other backgrounds, then present an overview of string theory on the plane-wave background, discussing the symmetries and spectrum. We then make precise the statement of the proposed duality, classify the BMN operators, and mention some extensions of the proposal. We move on to study the gauge theory side of the duality, studying both quantum and non-planar corrections to correlation functions of BMN operators, and their operator product expansion. The important issue of operator mixing and the resultant need for re-diagonalization is stressed. Finally, we study strings on the plane-wave via light-cone string field theory, and demonstrate agreement on the one-loop correction to the string mass spectrum and the corresponding quantity in the gauge theory. A new presentation of the relevant superalgebra is given.

  6. Liquid Water through Density-Functional Molecular Dynamics: Plane-Wave vs Atomic-Orbital Basis Sets.

    PubMed

    Miceli, Giacomo; Hutter, Jürg; Pasquarello, Alfredo

    2016-08-01

    We determine and compare structural, dynamical, and electronic properties of liquid water at near ambient conditions through density-functional molecular dynamics simulations, when using either plane-wave or atomic-orbital basis sets. In both frameworks, the electronic structure and the atomic forces are self-consistently determined within the same theoretical scheme based on a nonlocal density functional accounting for van der Waals interactions. The overall properties of liquid water achieved within the two frameworks are in excellent agreement with each other. Thus, our study supports that implementations with plane-wave or atomic-orbital basis sets yield equivalent results and can be used indiscriminately in study of liquid water or aqueous solutions.

  7. Liquid Water through Density-Functional Molecular Dynamics: Plane-Wave vs Atomic-Orbital Basis Sets.

    PubMed

    Miceli, Giacomo; Hutter, Jürg; Pasquarello, Alfredo

    2016-08-01

    We determine and compare structural, dynamical, and electronic properties of liquid water at near ambient conditions through density-functional molecular dynamics simulations, when using either plane-wave or atomic-orbital basis sets. In both frameworks, the electronic structure and the atomic forces are self-consistently determined within the same theoretical scheme based on a nonlocal density functional accounting for van der Waals interactions. The overall properties of liquid water achieved within the two frameworks are in excellent agreement with each other. Thus, our study supports that implementations with plane-wave or atomic-orbital basis sets yield equivalent results and can be used indiscriminately in study of liquid water or aqueous solutions. PMID:27434607

  8. Coded excitation plane wave imaging for shear wave motion detection.

    PubMed

    Song, Pengfei; Urban, Matthew W; Manduca, Armando; Greenleaf, James F; Chen, Shigao

    2015-07-01

    Plane wave imaging has greatly advanced the field of shear wave elastography thanks to its ultrafast imaging frame rate and the large field-of-view (FOV). However, plane wave imaging also has decreased penetration due to lack of transmit focusing, which makes it challenging to use plane waves for shear wave detection in deep tissues and in obese patients. This study investigated the feasibility of implementing coded excitation in plane wave imaging for shear wave detection, with the hypothesis that coded ultrasound signals can provide superior detection penetration and shear wave SNR compared with conventional ultrasound signals. Both phase encoding (Barker code) and frequency encoding (chirp code) methods were studied. A first phantom experiment showed an approximate penetration gain of 2 to 4 cm for the coded pulses. Two subsequent phantom studies showed that all coded pulses outperformed the conventional short imaging pulse by providing superior sensitivity to small motion and robustness to weak ultrasound signals. Finally, an in vivo liver case study on an obese subject (body mass index = 40) demonstrated the feasibility of using the proposed method for in vivo applications, and showed that all coded pulses could provide higher SNR shear wave signals than the conventional short pulse. These findings indicate that by using coded excitation shear wave detection, one can benefit from the ultrafast imaging frame rate and large FOV provided by plane wave imaging while preserving good penetration and shear wave signal quality, which is essential for obtaining robust shear elasticity measurements of tissue.

  9. Vector plane wave spectrum of an arbitrary polarized electromagnetic wave.

    PubMed

    Guo, Hanming; Chen, Jiabi; Zhuang, Songlin

    2006-03-20

    By using the method of modal expansions of the independent transverse fields, a formula of vector plane wave spectrum (VPWS) of an arbitrary polarized electromagnetic wave in a homogenous medium is derived. In this formula VPWS is composed of TM- and TE-mode plane wave spectrum, where the amplitude and unit polarized direction of every plane wave are separable, which has more obviously physical meaning and is more convenient to apply in some cases compared to previous formula of VPWS. As an example, the formula of VPWS is applied to the well-known radially and azimuthally polarized beam. In addition, vector Fourier-Bessel transform pairs of an arbitrary polarized electromagnetic wave with circular symmetry are also derived.

  10. Arrayed Ultrasonic Transducers on Arc Surface for Plane Wave Synthesis

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Soon; Kim, Jung-Ho; Kim, Moo-Joon; Ha, Kang-Lyeol; Yamada, Akira

    2004-05-01

    In ultrasonic computed tomography (UCT), it is necessary to synthesize a plane wave using waves emitted from sound sources arranged in the interior surface of a cylinder. In order to transmit a plane wave into a cylindrical surface, an ultrasonic transducer which has many vibrating elements with piezoelectric transverse effect arrayed on an arc surface is proposed. To achieve a wide beam width, the elements should have a small radiation area with a much narrow width. The measured electroacoustic efficiency for the elements was approximately 40% and the beam width defined by -3 dB level from the maximum was as wide as 120 deg. It was confirmed that plane wave synthesis is possible using the proposed transducer array.

  11. Vector plane wave spectrum of an arbitrary polarized electromagnetic wave

    NASA Astrophysics Data System (ADS)

    Guo, Hanming; Chen, Jiabi; Zhuang, Songlin

    2006-03-01

    By using the method of modal expansions of the independent transverse fields, a formula of vector plane wave spectrum (VPWS) of an arbitrary polarized electromagnetic wave in a homogenous medium is derived. In this formula VPWS is composed of TM- and TE-mode plane wave spectrum, where the amplitude and unit polarized direction of every plane wave are separable, which has more obviously physical meaning and is more convenient to apply in some cases compared to previous formula of VPWS. As an example, the formula of VPWS is applied to the well-known radially and azimuthally polarized beam. In addition, vector Fourier-Bessel transform pairs of an arbitrary polarized electromagnetic wave with circular symmetry are also derived.

  12. Pseudopotentials for correlated electron systems

    NASA Astrophysics Data System (ADS)

    Trail, J. R.; Needs, R. J.

    2013-07-01

    A scheme is developed for creating pseudopotentials for use in correlated-electron calculations. Pseudopotentials for the light elements H, Li, Be, B, C, N, O, and F, are reported, based on data from high-level quantum chemical calculations. Results obtained with these correlated electron pseudopotentials (CEPPs) are compared with data for atomic energy levels and the dissociation energies, molecular geometries, and zero-point vibrational energies of small molecules obtained from coupled cluster single double triple calculations with large basis sets. The CEPPs give better results in correlated-electron calculations than Hartree-Fock-based pseudopotentials available in the literature.

  13. Adaptive density partitioning technique in the auxiliary plane wave method

    NASA Astrophysics Data System (ADS)

    Kurashige, Yuki; Nakajima, Takahito; Hirao, Kimihiko

    2006-01-01

    We have developed the adaptive density partitioning technique (ADPT) in the auxiliary plane wave method, in which a part of the density is expanded to plane waves, for the fast evaluation of Coulomb matrix. Our partitioning is based on the error estimations and allows us to control the accuracy and efficiency. Moreover, we can drastically reduce the core Gaussian products that are left in Gaussian representation (its analytical integrals is the bottleneck in this method). For the taxol molecule with 6-31G** basis, the core Gaussian products accounted only for 5% in submicrohartree error.

  14. Improved fake mode free plane wave expansion method.

    PubMed

    Jiang, Bin; Zhou, Wenjun; Chen, Wei; Liu, Anjin; Zheng, Wanhua

    2011-08-01

    We analyze the origin of the fake modes introduced by the plane wave expansion method with three-dimension (3D) supercell approximation. Through the detailed analysis of the energy distribution of fake modes and real modes, we propose the plane wave expansion-three planar-slab waveguides method to remove the fake modes and obtain the fake mode free band structure of a two-dimensional air hole photonic crystal slab. To the best of our knowledge, this is the first time that such a fake mode free photonic crystal band structure is presented. Our method is also definitely useful in designing other 3D devices.

  15. Pseudopotential Calculation of the Excited States of Semiconductor Quantum Dots

    NASA Astrophysics Data System (ADS)

    Williamson, Andrew; Wang, Lin-Wang; Fu, Hiauxiang; Zunger, Alex

    1998-03-01

    We present the results of our pseudopotential calculations of up to 10 single-exciton states in free standing InP, InAs and CdSe quantum dots with diameters ranging from 10 to 50ÅIn the first step we solve for ≈20-40 single particle hole and electron states using a screened atomic pseudopotential Hamiltonian[1], solved within a plane wave basis using the Folded Spectrum Method[2]. In the second step, we calculate the electron-hole Coulomb energy[3] and the dipole transition probability for each of the ≈1000 possible single particle excitations. We present a comparison of the size scaling of the peaks in absorption and emission spectra obtained in our calculations with those from recent experiments and those of the effective mass based, k.p method. We also compare pseudopotential and k.p predictions of the character of the initial and final single particle states associated with each of these emission peaks. [1] J. Kim, A.J. Williamson, L.W. Wang, S.H-. Wei and A. Zunger, submitted to Phys. Rev. B [2] L. W. Wang and A. Zunger, J. Chem. Phys. 100, 2394 (1994). [3] A. Franceschetti and A. Zunger, Phys. Rev. Lett. 78, 915 (1997). *Supported under BES/OER/DMS contract No. DE---AC36---83CH10093

  16. A differentiated plane wave as an electromagnetic vortex

    NASA Astrophysics Data System (ADS)

    Hannay, J. H.; Nye, J. F.

    2015-04-01

    Differentiating a complex scalar plane wave with respect to its direction produces an isolated straight vortex line and has a natural extension, described in earlier papers, to the vector waves of electromagnetism—a differentiated plane wave (DPW). It epitomizes destructive interference and will be shown to have the local structure of an electromagnetic vortex. In this paper its polarization structure and Poynting vector field are compared and contrasted with that of the family of linear polynomial waves, of which it is a special member. By definition this wider family has a general linear complex vector function of position multiplying a plane wave, but the function must be such that the combination satisfies Maxwell’s equations. This forces translational invariance of the function along the wavevector direction—in other words the wave is ‘non-diffracting’. In a natural sense all possible polarizations are exhibited once only. But the DPW has a distinctive polarization structure only partly explored previously. Both classes of waves share similar Poynting vector fields, which can be ‘elliptic’ (helix-like flow lines) or ‘hyperbolic’, of a repulsive nature, unexpected for a vortex. Both classes can be considered as a limit in the superposition of three closely parallel ordinary plane waves in destructive interference, and this derivation is supplied in full here.

  17. An Apparatus for Constructing an Electromagnetic Plane Wave Model

    ERIC Educational Resources Information Center

    Kneubil, Fabiana Botelho; Loures, Marcus Vinicius Russo; Amado, William

    2015-01-01

    In this paper we report on an activity aimed at building an electromagnetic wave. This was part of a class on the concept of mass offered to a group of 20 pre-service Brazilian physics teachers. The activity consisted of building a plane wave using an apparatus in which it is possible to fit some rods representing electric and magnetic fields into…

  18. Shirley Reduced Basis DFT: plane-wave generality and accuracy at reduced computational cost

    NASA Astrophysics Data System (ADS)

    Hutchinson, Maxwell; Prendergast, David

    2014-03-01

    The Shirley Reduced Basis (SRB) provides a means for performing density functional theory electronic structure calculations with plane-wave accuracy and generality in a basis of significantly reduced size. The SRB is comprised of linear combinations of periodic Bloch functions sampled coarsely over the Brillouin zone (BZ) and selected for maximal information content using proper orthogonal decomposition [E. Shirley, Phys. Rev. B 54, 464 (1996)]. A basis produced from only order 10 samples, lying on the BZ boundary, is able to reproduce energies and stresses to sub meV and kbar accuracy, respectively, with order 10 basis functions per electronic band. Unlike other electronic structure bases of similar sizes, the SRB is adaptive and automatic, making no model assumptions beyond the use of pseudopotentials. We provide the first self-consistent implementation of this approach, enabling both relaxations and molecular dynamics. We demonstrate the usefulness of the method on a variety of physical systems, from crystalline solids to reduced dimensional systems under periodic boundary conditions, realizing order of magnitude performance improvements while kept within physically relevant error tolerances. M.H. acknowledges support from the DoE CSGF Program, Grant No. DE-FG02-97ER25308. Work by D.P. was performed at the Molecular Foundry, supported by the Office of Science, Office of Basic Energy Sciences, DoE under Contract No. DE-AC02-05CH11231.

  19. Ab initio Sternheimer-GW method for quasiparticle calculations using plane waves

    NASA Astrophysics Data System (ADS)

    Lambert, Henry; Giustino, Feliciano

    2013-08-01

    We report on the extension and implementation of the Sternheimer-GW method introduced by Giustino [Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.81.115105 81, 115105 (2010)] to the case of first-principles pseudopotential calculations based on a plane-waves basis. The Sternheimer-GW method consists of calculating the GW self-energy operator without resorting to the standard expansion over unoccupied Kohn-Sham electronic states. The Green's function is calculated by solving linear systems for frequencies along the real axis. The screened Coulomb interaction is calculated for frequencies along the imaginary axis by using the Sternheimer equation. Analytic continuation to the real axis is performed using Padé approximants. The generalized plasmon-pole approximation is avoided by performing explicit calculations at multiple frequencies using Frommer's multishift solver. We demonstrate our methodology by reporting tests on common insulators and semiconductors, including Si, diamond, LiCl, and SiC. Our calculated quasiparticle energies are in agreement with the results of fully converged calculations based on the sum-over-states approach. As the Sternheimer-GW method yields the complete self-energy Σ(r,r',ω) and not only its expectation values on Kohn-Sham states, this work opens the way to nonperturbative GW calculations and to direct calculations of spectral functions for angle-resolved photoemission spectroscopy. As an example of the capabilities of the method we calculate the G0W0 spectral functions of silicon and diamond.

  20. Calculating the density of states and optical-absorption spectra of large quantum systems by the plane-wave moments method

    NASA Astrophysics Data System (ADS)

    Wang, Lin-Wang

    1994-04-01

    The moments method is used to calculate the density of states and optical-absorption spectra of large quantum systems. This method uses random wave functions to calculate 500 Chebyshev moments of the density of states (5002 for the optical-absorption spectra), and transforms these moments back to energy space. The results compare well with direct calculations on a large, 2048 Si-atom bulklike supercell system. To demonstrate its utility, the spectra of a realistic quantum dot with 1035 Si and 452 H atoms are calculated using an empirical pseudopotential Hamiltonian and a plane-wave basis of wave functions.

  1. On the propagation of plane waves above an impedance surface

    NASA Technical Reports Server (NTRS)

    Zhong, F. H.; Vanmoorhem, W. K.

    1990-01-01

    The propagation of grazing incidence plane waves along a finite impedance boundary is investigated. A solution of the semi-infinite problem, where a harmonic motion, parallel to the boundary, is imposed along a line perpendicular to the boundary, is obtained. This solution consists of quasiplane waves, waves moving parallel to the boundary with amplitude and phase variations perpendicular to the boundary. Several approximations to the full solution are considered.

  2. Ultrafast vascular strain compounding using plane wave transmission.

    PubMed

    Hansen, H H G; Saris, A E C M; Vaka, N R; Nillesen, M M; de Korte, C L

    2014-03-01

    Deformations of the atherosclerotic vascular wall induced by the pulsating blood can be estimated using ultrasound strain imaging. Because these deformations indirectly provide information on mechanical plaque composition, strain imaging is a promising technique for differentiating between stable and vulnerable atherosclerotic plaques. This paper first explains 1-D radial strain estimation as applied intravascularly in coronary arteries. Next, recent methods for noninvasive vascular strain estimation in a transverse imaging plane are discussed. Finally, a compounding technique that our group recently developed is explained. This technique combines motion estimates of subsequently acquired focused ultrasound images obtained at various insonification angles. However, because the artery moves and deforms during the multi-angle acquisition, errors are introduced when compounding. Recent advances in computational power have enabled plane wave ultrasound acquisition, which allows 100 times faster image acquisition and thus might resolve the motion artifacts. In this paper the performance of strain imaging using plane wave compounding is investigated using simulations of an artery with a vulnerable plaque and experimental data of a two-layered vessel phantom. The results show that plane wave compounding outperforms 0° focused strain imaging. For the simulations, the root mean squared error reduced by 66% and 50% for radial and circumferential strain, respectively. For the experiments, the elastographic signal-to-noise and contrast-to-noise ratio (SNR(e) and CNR(e)) increased with 2.1 dB and 3.7 dB radially, and 5.6 dB and 16.2dB circumferentially. Because of the high frame rate, the plane wave compounding technique can even be further optimized and extended to 3D in future.

  3. Plane-wave expansion of elliptic cylindrical functions

    NASA Astrophysics Data System (ADS)

    Santini, Carlo; Frezza, Fabrizio; Tedeschi, Nicola

    2015-08-01

    Elliptic Cylindrical Waves (ECW), defined as the product of an angular Mathieu function by its corresponding radial Mathieu function, occur in the solution of scattering problems involving two-dimensional structures with elliptic cross sections. In this paper, we explicitly derive the expansion of ECW, along a plane surface, in terms of homogeneous and evanescent plane waves, showing the accuracy of the numerical implementation of the formulas and discussing possible applications of the result.

  4. Holography and entropy bounds in the plane wave matrix model

    SciTech Connect

    Bousso, Raphael; Mints, Aleksey L.

    2006-06-15

    As a quantum theory of gravity, matrix theory should provide a realization of the holographic principle, in the sense that a holographic theory should contain one binary degree of freedom per Planck area. We present evidence that Bekenstein's entropy bound, which is related to area differences, is manifest in the plane wave matrix model. If holography is implemented in this way, we predict crossover behavior at strong coupling when the energy exceeds N{sup 2} in units of the mass scale.

  5. CONDENSED MATTER: STRUCTURE, THERMAL AND MECHANICAL PROPERTIES: Pseudo-potential investigations of structural, elastic and thermal properties of tungsten disilicide

    NASA Astrophysics Data System (ADS)

    Xu, Guo-Liang; Chen, Jing-Dong; Xia, Yao-Zheng; Liu, Xue-Feng

    2009-08-01

    The plane-wave pseudopotential method using the generalized gradient approximation within the density functional theory is used to investigate the structure and bulk modulus of WSi2. The quasi-harmonic Debye model, using a set of total energy versus cell volume obtained with the plane-wave pseudopotential method, is applied to the study of the elastic properties and vibrational effects. We have analysed the bulk modulus of WSi2 up to 1600 K. The major trend shows that the WSi2 crystal becomes more compressible when the temperature rises and the increase of compressibility leads to the decrease of Debye temperature. The predicted temperature and pressure effects on the thermal expansion, heat capacity and Debye temperatures are determined from the non-equilibrium Gibbs functions and compared with the data available.

  6. Stolt's f-k migration for plane wave ultrasound imaging.

    PubMed

    Garcia, Damien; Le Tarnec, Louis; Muth, Stéphan; Montagnon, Emmanuel; Porée, Jonathan; Cloutier, Guy

    2013-09-01

    Ultrafast ultrasound is an emerging modality that offers new perspectives and opportunities in medical imaging. Plane wave imaging (PWI) allows one to attain very high frame rates by transmission of planar ultrasound wave-fronts. As a plane wave reaches a given scatterer, the latter becomes a secondary source emitting upward spherical waves and creating a diffraction hyperbola in the received RF signals. To produce an image of the scatterers, all the hyperbolas must be migrated back to their apexes. To perform beamforming of plane wave echo RFs and return high-quality images at high frame rates, we propose a new migration method carried out in the frequency-wavenumber (f-k) domain. The f-k migration for PWI has been adapted from the Stolt migration for seismic imaging. This migration technique is based on the exploding reflector model (ERM), which consists in assuming that all the scatterers explode in concert and become acoustic sources. The classical ERM model, however, is not appropriate for PWI. We showed that the ERM can be made suitable for PWI by a spatial transformation of the hyperbolic traces present in the RF data. In vitro experiments were performed to outline the advantages of PWI with Stolt's f-k migration over the conventional delay-and-sum (DAS) approach. The Stolt's f-k migration was also compared with the Fourier-based method developed by J.-Y. Lu. Our findings show that multi-angle compounded f-k migrated images are of quality similar to those obtained with a stateof- the-art dynamic focusing mode. This remained true even with a very small number of steering angles, thus ensuring a highly competitive frame rate. In addition, the new FFT-based f-k migration provides comparable or better contrast-to-noise ratio and lateral resolution than the Lu's and DAS migration schemes. Matlab codes for the Stolt's f-k migration for PWI are provided. PMID:24626107

  7. Stolt's f-k migration for plane wave ultrasound imaging.

    PubMed

    Garcia, Damien; Le Tarnec, Louis; Muth, Stéphan; Montagnon, Emmanuel; Porée, Jonathan; Cloutier, Guy

    2013-09-01

    Ultrafast ultrasound is an emerging modality that offers new perspectives and opportunities in medical imaging. Plane wave imaging (PWI) allows one to attain very high frame rates by transmission of planar ultrasound wave-fronts. As a plane wave reaches a given scatterer, the latter becomes a secondary source emitting upward spherical waves and creating a diffraction hyperbola in the received RF signals. To produce an image of the scatterers, all the hyperbolas must be migrated back to their apexes. To perform beamforming of plane wave echo RFs and return high-quality images at high frame rates, we propose a new migration method carried out in the frequency-wavenumber (f-k) domain. The f-k migration for PWI has been adapted from the Stolt migration for seismic imaging. This migration technique is based on the exploding reflector model (ERM), which consists in assuming that all the scatterers explode in concert and become acoustic sources. The classical ERM model, however, is not appropriate for PWI. We showed that the ERM can be made suitable for PWI by a spatial transformation of the hyperbolic traces present in the RF data. In vitro experiments were performed to outline the advantages of PWI with Stolt's f-k migration over the conventional delay-and-sum (DAS) approach. The Stolt's f-k migration was also compared with the Fourier-based method developed by J.-Y. Lu. Our findings show that multi-angle compounded f-k migrated images are of quality similar to those obtained with a stateof- the-art dynamic focusing mode. This remained true even with a very small number of steering angles, thus ensuring a highly competitive frame rate. In addition, the new FFT-based f-k migration provides comparable or better contrast-to-noise ratio and lateral resolution than the Lu's and DAS migration schemes. Matlab codes for the Stolt's f-k migration for PWI are provided.

  8. Numerical errors of diffraction computing using plane wave spectrum decomposition

    NASA Astrophysics Data System (ADS)

    Kozacki, Tomasz

    2008-09-01

    In the paper the numerical determination of diffraction patterns using plane wave spectrum decomposition (PWS) is investigated. The simple formula for sampling selection for error-free numerical computation is proposed and its applicability is discussed. The usage of this formula presents practical difficulty for some diffraction problems due to required large memory load. A new multi-Fourier transform PWS (MPWS) method is elaborated which overcomes memory requirement of the PWS method. The performances of the PWS and MPWS methods are verified through extensive numerical simulations.

  9. Decoding the matrix: Coincident membranes on the plane wave

    SciTech Connect

    Bousso, Raphael; Mints, Aleksey L.

    2006-03-15

    At the core of nonperturbative theories of quantum gravity lies the holographic encoding of bulk data in large matrices. At present this mapping is poorly understood. The plane wave matrix model provides a laboratory for isolating aspects of this problem in a controlled setting. At large boosts, configurations of concentric membranes become superselection sectors, whose exact spectra are known. From the bulk point of view, one expects product states of individual membranes to be contained within the full spectrum. However, for non-BPS states this inclusion relation is obscured by Gauss law constraints. Its validity rests on nontrivial relations in representation theory, which we identify and verify by explicit computation.

  10. Various approximations made in augmented-plane-wave calculations

    NASA Astrophysics Data System (ADS)

    Bacalis, N. C.; Blathras, K.; Thomaides, P.; Papaconstantopoulos, D. A.

    1985-10-01

    The effects of various approximations used in performing augmented-plane-wave calculations were studied for elements of the fifth and sixth columns of the Periodic Table, namely V, Nb, Ta, Cr, Mo, and W. Two kinds of approximations have been checked: (i) variation of the number of k points used to iterate to self-consistency, and (ii) approximations for the treatment of the core states. In addition a comparison between relativistic and nonrelativistic calculations is made, and an approximate method of calculating the spin-orbit splitting is given.

  11. Waveguide characteristics of coupled in-plane waves.

    PubMed

    Pan, Jie; Lu, Jing; Qiu, Xiaojun

    2012-06-01

    In-plane waves in a waveguide made from a thin plate are described by a superposition of a set of orthogonal functions that satisfy the edge conditions of the waveguide. Due to the Poisson and shear effects, the displacement components of the in-plane waves along the two in-plane orthogonal coordinates are coupled and this coupling affects the propagation and spatial properties of the waveguide modes. The orthogonal functions and their associated wavenumbers represent the characteristics of the uncoupled modes of the waveguide where the above mentioned couplings are ignored. This study demonstrates that the characteristics of the waveguide modes are determined by the couplings of the uncoupled mode pairs, which become significant when the pairs satisfy the conditions of spatial coincidence. At some frequencies, certain waveguide modes can be determined by a single pair of uncoupled modes. For this case, the analytical solution for the waveguide modes exists and provides both a qualitative and quantitative interpretation of the characteristics of the waveguide mode.

  12. The implementation of holography in the plane wave matrix model

    NASA Astrophysics Data System (ADS)

    Mints, Aleksey Leonidovich

    It is expected that at the core of nonperturbative theories of quantum gravity, such as M-theory, lies the realization of the holographic principle, in the sense that a holographic theory should contain one binary degree of freedom per Planck area. Present understanding of such theories requires the holographic encoding of bulk data in large matrices. Currently this mapping is poorly understood. The plane wave matrix model provides a laboratory for isolating aspects of this problem in a controlled setting. At large boosts, configurations of concentric membranes become superselection sectors, whose exact spectra are known. From the bulk point of view one expects product states of individual membranes to be contained within the full spectrum. However, for non-BPS states this inclusion relation is obscured by Gauss law constraints. Its validity rests on nontrivial relations in representation theory, which we identify and verify by explicit computation. Beyond the decoding and partial identification of selected states in large matrices, one would like to get a better understanding of the holographic state counting of these degrees of freedom, i.e., entropy. Contrary to the naive expectation of holography realized in terms of the covariant entropy bound, we present evidence that it is the Bekenstein entropy bound, which is related to area differences, that is manifest in the plane wave matrix model. If holography is implemented in this way, we predict crossover behavior at strong coupling when the energy exceeds N2 in units of the mass scale.

  13. Ultrasoft pseudopotentials for lanthanide solvation complexes: core or valence character of the 4f electrons.

    PubMed

    Pollet, Rodolphe; Clavaguéra, Carine; Dognon, Jean-Pierre

    2006-04-28

    The 4f electrons of lanthanides, because of their strong localization in the region around the nucleus, are traditionally included in a pseudopotential core. This approximation is scrutinized by optimizing the structures and calculating the interaction energies of Gd(3+)(H(2)O) and Gd(3+)(NH(3)) microsolvation complexes within plane wave Perdew-Burke-Ernzerhof calculations using ultrasoft pseudopotentials where the 4f electrons are included either in the core or in the valence space. Upon comparison to quantum chemical MP2 and CCSD(T) reference calculations it is found that the explicit treatment of the 4f electrons in the valence shell yields quite accurate results including the required small spin polarization due to ligand charge transfer with only modest computational overhead.

  14. Superstring theory in AdS(3) and plane waves

    NASA Astrophysics Data System (ADS)

    Son, John Sang Won

    This thesis is devoted to the study of string theory in AdS 3 and its applications to recent developments in string theory. The difficulties associated with formulating a consistent string theory in AdS3 and its underlying SL(2, R) WZW model are explained. We describe how these difficulties can be overcome by assuming that the SL(2, R) WZW model contains spectral flow symmetry. The existence of spectral flow symmetry in the fully quantum treatment is proved by a calculation of the one-loop string partition function. We consider Euclidean AdS 3 with the time direction periodically identified, and compute the torus partition function in this background. The string spectrum can be reproduced by viewing the one-loop calculation as the free energy of a gas of strings, thus providing a rigorous proof of the results based on spectral flow arguments. Next, we turn to spacetimes that are quotients of AdS 3, which include the BTZ black hole and conical spaces. Strings propagating in the conical space are described by taking an orbifold of strings in AdS3. We show that the twisted states of these orbifolds can be obtained by fractional spectral flow. We show that the shift in the ground state energy usually associated with orbifold twists is absent in this case, and offer a unified framework in which to view spectral flow. Lastly, we consider the RNS superstrings in AdS 3 x S3 x M , where M may be K3 or T 4, based on supersymmetric extensions of SL(2, R) and SU(2) WZW models. We construct the physical states and calculate the spectrum. A subsector of this theory describes strings propagating in the six dimensional plane wave obtained by the Penrose limit of AdS3 x S3 x M . We reproduce the plane wave spectrum by taking J and the radius to infinity. We show that the plane wave spectrum actually coincides with the large J spectrum at fixed radius, i.e. in AdS3 x S3. Relation to some recent topics of interest such as the Frolov-Tseytlin string and strings with critical tension

  15. Initial Operation of S-Band Plane Wave Transformer Photoinjector

    NASA Astrophysics Data System (ADS)

    Ding, Xiaodong; Pellegrini, Claudio; Rosenzweig, James; Telfer, Soren; Physics, Dept Of; Astronomy Team

    2000-04-01

    An integrated S-Band RF photoinjector based on the plane wave transformer (PWT) is being built and operated in the Particle Beam Physics Laboratory at UCLA. This novel structure integrates a photocathode directly into a PWT Linac making the structure simple and compact. Due to the strong coupling between each adjacent cell, this structure is relatively easy to fabricate and operate. This photoinjector can provide high brightness beams at energies of 15 to 20MeV, with emittance less than 1mm-mrad at charge of 1 nC. These short-pulse beams can be used in various applications: space charge dominated beam physics studies, plasma lenses, plasma accelerators, free-electron laser microbunching techniques, and SASE-FEL physics studies. It will also provide commercial opportunities in chemistry, biology and medicine. The initial operation of the PWT photoinjector with high RF power is described. A comparation of experimental result and theoretical design is also discussed.

  16. Gravitational scattering of zero-rest-mass plane waves

    NASA Technical Reports Server (NTRS)

    De Logi, W. K.; Kovacs, S. J., Jr.

    1977-01-01

    The Feyman-diagram technique is used to calculate the differential cross sections for the scattering of zero-rest-mass plane waves of spin 0, 1, and 2 by linearized Schwarzschild and Kerr geometries in the long-wavelength weak-field limit. It is found that the polarization of right (or left) circularly polarized electromagnetic waves is unaffected by the scattering process (i.e., helicity is conserved) and that the two helicity (polarization) states of the photon are scattered differently by the Kerr geometry. This coupling between the photon helicity and the angular momentum of the scatterer also leads to a partial polarization of unpolarized incident light. For gravitational waves, on the other hand, there is neither helicity conservation nor helicity-dependent scattering; the angular momentum of the scatterer has no polarizing effect on incident unpolarized gravitational waves.

  17. Six-mm, plane-wave shock driver

    NASA Astrophysics Data System (ADS)

    Frank, Alan M.; Chau, Henry H.

    1994-07-01

    A 6-mm-diameter, plane-wave shock generation system has been developed and characterized as a laboratory bench driver for small scale experiments. The driver is based on an exploding-foil-driven slapper used either directly or to initiate an HE pellet. The slapper is driven by a low-inductance fireset with burst currents on the order of 30 kA and burst times of about 250 ns, with time-to-burst jitter under 10 ns. Both the slapper impact and the detonation breakout of the pellet have been measured to be flat to within 10 ns over a 6-mm diameter. Fabry-Perot velocimetry of impacts with LiF crystals were used to characterize shock pressures and durations. Attenuator plates and flyers driven by the HE were also measured, which provided a variety of available pulse shapes and data for modeling efforts.

  18. Six-mm, plane-wave shock driver

    SciTech Connect

    Frank, A.M.; Chau, H.H.

    1993-06-14

    A 6-mm-diameter, plane-wave shock generation system has been developed and characterized as a laboratory bench driver for small scale experiments. The driver is based on an exploding-foil-driven slapper used either directly or to initiate an HE pellet. The slapper is driven by a low-inductance fireset with burst currents on the order of 30 kA and burst times of about 250ns, with a time-to-burst jitter under 10ns. Both the slapper impact and the detonation breakout of the pellet have been measured to be flat to within 10ns over a 6-mm diameter. Fabry-Perot velocimetry of impacts with LiF crystals were used to characterize shock pressures and durations. Attenuator plates and flyers driven by the HE were also measured, which provided a variety of available pulse shapes and data for modeling efforts.

  19. Six-mm, plane-wave shock driver

    SciTech Connect

    Frank, A.M.; Chau, H.H. )

    1994-07-10

    A 6-mm-diameter, plane-wave shock generation system has been developed and characterized as a laboratory bench driver for small scale experiments. The driver is based on an exploding-foil-driven slapper used either directly or to initiate an HE pellet. The slapper is driven by a low-inductance fireset with burst currents on the order of 30 kA and burst times of about 250 ns, with time-to-burst jitter under 10 ns. Both the slapper impact and the detonation breakout of the pellet have been measured to be flat to within 10 ns over a 6-mm diameter. Fabry-Perot velocimetry of impacts with LiF crystals were used to characterize shock pressures and durations. Attenuator plates and flyers driven by the HE were also measured, which provided a variety of available pulse shapes and data for modeling efforts. [copyright]American Institute of Physics

  20. Inhomogeneous plane wave and the most energetic complex ray.

    PubMed

    Deschamps, M; Poncelet, O

    2002-05-01

    This paper presents a study on the wave surfaces of anisotropic solids. In addition to the classical and real rays, which are defined by the normal to the slowness surfaces, it is obtained complex rays, which are associated to specific inhomogeneous plane waves. Referring to the complex Christoffel's equation and to the Fermat's principle, an intrinsic equation can be associated to these complex rays. Limiting the study to principal planes and plotting the associated complex wave surfaces, it can be shown that four energetic rays always exist in any directions for both quasi-isotropic and anisotropic media (even beyond the cusp). Consequently, it is always possible to define four closed wave surfaces (real or not). PMID:12159950

  1. Partial-wave expansions of angular spectra of plane waves.

    PubMed

    Lock, James A

    2006-11-01

    Focused electromagnetic beams are frequently modeled by either an angular spectrum of plane waves or a partial-wave sum of spherical multipole waves. The connection between these two beam models is explored here. The partial-wave expansion of an angular spectrum containing evanescent components is found to possess only odd partial waves. On the other hand, the partial-wave expansion of an alternate angular spectrum constructed so as to be free of evanescent components contains all partial waves but describes a propagating beam with a small amount of standing-wave component mixed in. A procedure is described for minimizing the standing-wave component so as to more accurately model a purely forward propagating experimental beam.

  2. Plane-wave spectrum approach for tilted waveguides.

    PubMed

    Einziger, P D; Salzman, J

    1988-12-01

    Scattering of guided modes from an abruptly terminated waveguide is analyzed through an integral-equation formulation. First the boundary-value problem for a plane-stratified waveguide with arbitrary profile is reduced to a canonical system of surface integral equations. A Born-type iterative procedure is then employed to obtain a tractable solution of the scattering field at the termination. The specific choice of a tilted planar termination renders an explicit closed-form expression for the first Born approximation, represented by the plane-wave spectrum of the incident modal field modified by the appropriate Fresnel coefficient. Thus previous ad hoc formulations can be recovered as limiting cases of the suggested rigorous expansion scheme.

  3. Reflectarray Demonstrated to Transform Spherical Waves into Plane Waves

    NASA Technical Reports Server (NTRS)

    Zaman, Afrosz J.

    1998-01-01

    The development of low-cost, high-efficiency array antennas has been the research focus of NASA Lewis Research Center's Communications Technology Division for the past 15 years. One area of current interest is reflectarray development. Reflectarrays have generally been used to replace reflector antennas. In this capacity, different configurations (such as prime focus and offset) and various applications (such as dual frequency and scanning) have been demonstrated with great success. One potential application that has not been explored previously is the use of reflectarrays to compensate for phase errors in space-power-combining applications, such as a space-fed lens and power-combining amplifiers. Recently, we experimentally investigated the feasibility of using a reflectarray as an alternative to a dielectric lens for such applications. The experiment involved transforming the spherical waves from an orthomode horn to plane waves at the horn aperture. The reflectarray consists of square patches terminated in open stubs to provide the necessary phase compensation.

  4. Ultrafast acousto-optic imaging with ultrasonic plane waves.

    PubMed

    Laudereau, Jean-Baptiste; Grabar, Alexander A; Tanter, Mickaël; Gennisson, Jean-Luc; Ramaz, François

    2016-02-22

    Due to multiple light scattering inside biological tissues, deep non-invasive optical medical imaging is very challenging. Acousto-optic imaging is a technique coupling ultrasound and light that allows recovering optical contrast at depths of few centimeters with a millimeter resolution. Recent advances in acousto-optic imaging are using short focused ultrasound pulses often averaged over several hundred or thousand pulses. As the pulsing rate of commercial probes is limited to about few ultrasound cycles every 100 μs, acquiring an acousto-optic image usually takes several tens of seconds due to the high number of acoustic pulses excitation. We propose here a new acousto-optic imaging technique based on the use of ultrasound plane waves instead of focused ones that allows increasing drastically the imaging rate. PMID:26907033

  5. Partial-wave expansions of angular spectra of plane waves

    NASA Astrophysics Data System (ADS)

    Lock, James A.

    2006-11-01

    Focused electromagnetic beams are frequently modeled by either an angular spectrum of plane waves or a partial-wave sum of spherical multipole waves. The connection between these two beam models is explored here. The partial-wave expansion of an angular spectrum containing evanescent components is found to possess only odd partial waves. On the other hand, the partial-wave expansion of an alternate angular spectrum constructed so as to be free of evanescent components contains all partial waves but describes a propagating beam with a small amount of standing-wave component mixed in. A procedure is described for minimizing the standing-wave component so as to more accurately model a purely forward propagating experimental beam.

  6. The angular apodization in coherent plane-wave compounding.

    PubMed

    Rodriguez-Molares, Alfonso; Torp, Hans; Denarie, Bastien; Løvstakken, Lasse

    2015-11-01

    This article describes the relation between apodization in conventional focused imaging and apodization in coherent plane-wave compounding (CPWC). We pose the hypothesis that equivalent transmit beams can be produced with both methods if the transmit apodization is adequately transformed. We derive a relation between apodization in CPWC and in synthetic transmit aperture imaging (STAI), which we argue to be equivalent to conventional optimal multifocus imaging. We find that under certain conditions, the transformation of the apodization becomes trivial and the same window used in STAI can be applied for CPWC but extended to the whole angle sequence. We test the hypothesis with in silico data and find that the transformed apodization accurately mimics the objective transmit apodization, with differences in the lateral resolution between 3% and 6%. PMID:26559630

  7. Wind velocity profile reconstruction from intensity fluctuations of a plane wave propagating in a turbulent atmosphere.

    PubMed

    Banakh, V A; Marakasov, D A

    2007-08-01

    Reconstruction of a wind profile based on the statistics of plane-wave intensity fluctuations in a turbulent atmosphere is considered. The algorithm for wind profile retrieval from the spatiotemporal spectrum of plane-wave weak intensity fluctuations is described, and the results of end-to-end computer experiments on wind profiling based on the developed algorithm are presented. It is shown that the reconstructing algorithm allows retrieval of a wind profile from turbulent plane-wave intensity fluctuations with acceptable accuracy.

  8. Transfer matrix approach to propagation of angular plane wave spectra through metamaterial multilayer structures

    NASA Astrophysics Data System (ADS)

    Banerjee, Partha P.; Li, Han; Aylo, Rola; Nehmetallah, Georges

    2011-10-01

    The development of electromagnetic (EM) metamaterials for perfect lensing and optical cloaking has given rise to novel multilayer bandgap structures using stacks of positive and negative index materials. Propagation of a collection of TE or TM plane waves, comprising the angular plane wave spectrum, through such structures is analyzed by using the transfer matrix method (TMM) on every plane wave component. Results obtained from this TMM approach for a Gaussian spectrum are compared with those using standard FEM techniques.

  9. Condition for invariant spectral degree of coherence of an electromagnetic plane wave on scattering

    NASA Astrophysics Data System (ADS)

    Li, Jia; Chen, Yanru; Xu, Shixue; Wang, Yongqing; Zhou, Muchun; Zhao, Qi; Xin, Yu; Chen, Feinan

    2011-02-01

    Within the accuracy of the first-order Born approximation, the condition for invariant spectral degree of coherence of an electromagnetic plane wave scattered from random media is presented. The condition for the electromagnetic plane wave is different from the one for the scalar plane wave. Results also indicate that, different polarizations of the incident plane wave would have essential effects on analytical forms of the condition. These effects may be due to the correlation-induced changes in the scattered spectral degree of coherence.

  10. Development of the plane wave transformer photoelectron linear accelerator

    NASA Astrophysics Data System (ADS)

    Ding, Xiaodong

    2000-11-01

    The design, fabrication and characterization of the UCLA integrated S-Band RF photocathode electron linear accelerator (Linac) based on the plane wave transformer (PWT) structure is presented. This new generation photoinjector integrates a photocathode directly into a PWT linac making the structure simple and compact. Due to the strong coupling between each adjacent cell, the PWT structure is relatively easy to fabricate and operate. This photoinjector can provide high brightness beams at energies of 15 to 20MeV, with emittance less than 1mm.mrad at charge of 1 nC [3]. These short-pulse beams can be used in various applications: space charge dominated beam physics studies, plasma lenses, plasma accelerators, free-electron laser microbunching techniques, and SASE-FEL physics studies. It will also provide commercial opportunities in chemistry, biology and medicine. The principle of photoelectron gun setup, accelerating structure design and beam dynamic study is described. The design, fabrication and testing of this UCLA 10 full cell and 2 half cell PWT structure is discussed in detail. The results of Microwave measurements and first step high power test have showed the success of the UCLA PWT photoinjector design. The measurement results met all the design goals and operation requirements. The experimental requirements for the beam diagnostics are also presented.

  11. Acoustic plane wave preferential orientation of metal oxide superconducting materials

    DOEpatents

    Tolt, Thomas L.; Poeppel, Roger B.

    1991-01-01

    A polycrystalline metal oxide such as YBa.sub.2 Cu.sub.3 O.sub.7-X (where 0plane wave in the acoustic or ultrasonic frequency range (either progressive or standing) in applying a torque to each crystal particle. The ceramic slip is then set and fired by conventional methods to produce a conductor with preferentially oriented grains and substantially enhanced current carrying capacity.

  12. NMR Shielding in Metals Using the Augmented Plane Wave Method

    PubMed Central

    2015-01-01

    We present calculations of solid state NMR magnetic shielding in metals, which includes both the orbital and the complete spin response of the system in a consistent way. The latter contains an induced spin-polarization of the core states and needs an all-electron self-consistent treatment. In particular, for transition metals, the spin hyperfine field originates not only from the polarization of the valence s-electrons, but the induced magnetic moment of the d-electrons polarizes the core s-states in opposite direction. The method is based on DFT and the augmented plane wave approach as implemented in the WIEN2k code. A comparison between calculated and measured NMR shifts indicates that first-principle calculations can obtain converged results and are more reliable than initially concluded based on previous publications. Nevertheless large k-meshes (up to 2 000 000 k-points in the full Brillouin-zone) and some Fermi-broadening are necessary. Our results show that, in general, both spin and orbital components of the NMR shielding must be evaluated in order to reproduce experimental shifts, because the orbital part cancels the shift of the usually highly ionic reference compound only for simple sp-elements but not for transition metals. This development paves the way for routine NMR calculations of metallic systems. PMID:26322148

  13. Photoelectron wave function in photoionization: plane wave or Coulomb wave?

    PubMed

    Gozem, Samer; Gunina, Anastasia O; Ichino, Takatoshi; Osborn, David L; Stanton, John F; Krylov, Anna I

    2015-11-19

    The calculation of absolute total cross sections requires accurate wave functions of the photoelectron and of the initial and final states of the system. The essential information contained in the latter two can be condensed into a Dyson orbital. We employ correlated Dyson orbitals and test approximate treatments of the photoelectron wave function, that is, plane and Coulomb waves, by comparing computed and experimental photoionization and photodetachment spectra. We find that in anions, a plane wave treatment of the photoelectron provides a good description of photodetachment spectra. For photoionization of neutral atoms or molecules with one heavy atom, the photoelectron wave function must be treated as a Coulomb wave to account for the interaction of the photoelectron with the +1 charge of the ionized core. For larger molecules, the best agreement with experiment is often achieved by using a Coulomb wave with a partial (effective) charge smaller than unity. This likely derives from the fact that the effective charge at the centroid of the Dyson orbital, which serves as the origin of the spherical wave expansion, is smaller than the total charge of a polyatomic cation. The results suggest that accurate molecular photoionization cross sections can be computed with a modified central potential model that accounts for the nonspherical charge distribution of the core by adjusting the charge in the center of the expansion.

  14. Photoelectron wave function in photoionization: plane wave or Coulomb wave?

    PubMed

    Gozem, Samer; Gunina, Anastasia O; Ichino, Takatoshi; Osborn, David L; Stanton, John F; Krylov, Anna I

    2015-11-19

    The calculation of absolute total cross sections requires accurate wave functions of the photoelectron and of the initial and final states of the system. The essential information contained in the latter two can be condensed into a Dyson orbital. We employ correlated Dyson orbitals and test approximate treatments of the photoelectron wave function, that is, plane and Coulomb waves, by comparing computed and experimental photoionization and photodetachment spectra. We find that in anions, a plane wave treatment of the photoelectron provides a good description of photodetachment spectra. For photoionization of neutral atoms or molecules with one heavy atom, the photoelectron wave function must be treated as a Coulomb wave to account for the interaction of the photoelectron with the +1 charge of the ionized core. For larger molecules, the best agreement with experiment is often achieved by using a Coulomb wave with a partial (effective) charge smaller than unity. This likely derives from the fact that the effective charge at the centroid of the Dyson orbital, which serves as the origin of the spherical wave expansion, is smaller than the total charge of a polyatomic cation. The results suggest that accurate molecular photoionization cross sections can be computed with a modified central potential model that accounts for the nonspherical charge distribution of the core by adjusting the charge in the center of the expansion. PMID:26509428

  15. Plane-wave theory of three-dimensional magnonic crystals

    NASA Astrophysics Data System (ADS)

    Krawczyk, M.; Puszkarski, H.

    2008-02-01

    We use the plane-wave method to determine spin-wave spectra of three-dimensional magnonic crystals (the magnetic counterpart of photonic crystals) composed of two different ferromagnetic materials. The scattering centers in the magnonic crystal considered are ferromagnetic spheroids (spheres being a special case) distributed in sites of a cubic (sc, fcc, or bcc) lattice embedded in a matrix of a different ferromagnetic material. We demonstrate that magnonic gaps in such structures occur at spontaneous magnetization contrast and/or exchange contrast values above a certain critical level, which depends on the lattice type. Optimum conditions for magnonic gaps to open are offered by the structure in which the scattering centers are the most densely packed (the fcc lattice). We show that in all three lattice types considered the reduced width of the gap (i.e., the width referred to the gap center) is, in good approximation, a linear function of both the exchange contrast and the magnetization contrast. Also, the gap width proves sensitive to scattering center deformation, and its maximum value to correspond to a scattering center shape close to a sphere. Moreover, our numerical results seem to indicate that dipolar interactions in general result in an effective reduction of the gap width, but their impact only becomes of importance when the lattice constant of the cubic magnonic structure is greater than the ferromagnetic exchange length of the matrix material.

  16. The plain truth about forming a plane wave of neutrons

    NASA Astrophysics Data System (ADS)

    Wagh, Apoorva G.; Abbas, Sohrab; Treimer, Wolfgang

    2011-04-01

    We have attained the first sub-arcsecond collimation of a monochromatic neutron beam by diffracting neutrons from a Bragg prism, viz. a single crystal prism operating in the vicinity of Bragg incidence. Analytical as well numerical computations based on the dynamical diffraction theory, led to the optimised collimator configuration of a silicon {1 1 1} Bragg prism for 5.26 Å neutrons. We fabricated a Bragg prism to these specifications, tested and operated it at the double diffractometer setup in Helmholtz Zentrum Berlin to produce a 0.58 arcsec wide monochromatic neutron beam. With a similarly optimised Bragg prism analyser of opposite asymmetry, we recorded a 0.62 arcsec wide virgin rocking curve for this ultra-parallel beam. With this nearly plane-wave neutron beam, we have recorded the first ever USANS spectrum in Q˜10-6 Å-1 range with a hydroxyapatite casein protein sample and demonstrated the instrument capability to characterise agglomerates up to 150 μm in size. The super-collimated monochromatic beam has also enabled us to record the first neutron diffraction pattern from a macroscopic grating of 200 μm period. The transverse coherence length of 175 μm (FWHM) of the ultra-parallel beam derived from the analysis of this pattern, is the greatest achieved to date for Å wavelength neutrons.

  17. Compressed plane waves yield a compactly supported multiresolution basis for the Laplace operator.

    PubMed

    Ozoliņš, Vidvuds; Lai, Rongjie; Caflisch, Russel; Osher, Stanley

    2014-02-01

    This paper describes an L1 regularized variational framework for developing a spatially localized basis, compressed plane waves, that spans the eigenspace of a differential operator, for instance, the Laplace operator. Our approach generalizes the concept of plane waves to an orthogonal real-space basis with multiresolution capabilities.

  18. Green's function of the strip-slab guide by plane-wave-spectrum synthesis

    NASA Astrophysics Data System (ADS)

    Sen, T. K.; Basuray, A.; Datta, A. K.

    1987-11-01

    The application of the plane-wave-spectrum method to strip-slab waveguides is described. The dispersion equation of the structure is first evaluated from the condition of self-consistency of rays. By treating the modes as the superpositions of plane waves, Green's function for the structure is subsequently derived.

  19. Tailored complex 3D vortex lattice structures by perturbed multiples of three-plane waves.

    PubMed

    Xavier, Jolly; Vyas, Sunil; Senthilkumaran, Paramasivam; Joseph, Joby

    2012-04-20

    As three-plane waves are the minimum number required for the formation of vortex-embedded lattice structures by plane wave interference, we present our experimental investigation on the formation of complex 3D photonic vortex lattice structures by a designed superposition of multiples of phase-engineered three-plane waves. The unfolding of the generated complex photonic lattice structures with higher order helical phase is realized by perturbing the superposition of a relatively phase-encoded, axially equidistant multiple of three noncoplanar plane waves. Through a programmable spatial light modulator assisted single step fabrication approach, the unfolded 3D vortex lattice structures are experimentally realized, well matched to our computer simulations. The formation of higher order intertwined helices embedded in these 3D spiraling vortex lattice structures by the superposition of the multiples of phase-engineered three-plane waves interference is also studied.

  20. Ultrasoft pseudopotentials and Hubbard U values for rare-earth elements (Re=La-Lu) guided by HSE06 calculations

    NASA Astrophysics Data System (ADS)

    Topsakal, Mehmet; Umemoto, Koichiro; Wentzcovitch, Renata

    2014-03-01

    The lanthanide series of the periodic table comprises fifteen members ranging from La to Lu - the rare-earth (Re) elements. They exhibit unique (and mostly unexplored) chemical properties depending on the fillings of 4f-orbitals. Due to strong electronic correlation, 4f valence electrons are incorrectly described by standard DFT functionals. In order to cope with these inefficiencies, the DFT+U method is often employed where Hubbard-type U is introduced into the standard DFT. Another approach is to use hybrid functionals. Both improve the treatment of strongly correlated electrons. However, DFT+U suffers from ambiguity of U while hybrid functionals suffer from extremely demanding computational costs. Here we provide Vanderbilt type ultrasoft pseudopotentials for Re elements with suggested U values allowing efficient plane-wave calculations. Hubbard U values are determined according to HSE06 calculations on Re-nitrides (ReN). Generated pseudopotentials were further tested on some Re-cobaltite (Re-CoO3) perovskites. Alternative pseudopotentials with f-electrons kept frozen in the core of pseudopotential are also provided and possible outcomes are addressed. We believe that these new pseudopotentials with suggested U values will allow further studies on rare-earth materials.

  1. Pseudopotential Method for Higher Partial Wave Scattering

    SciTech Connect

    Idziaszek, Zbigniew; Calarco, Tommaso

    2006-01-13

    We present a zero-range pseudopotential applicable for all partial wave interactions between neutral atoms. For p and d waves, we derive effective pseudopotentials, which are useful for problems involving anisotropic external potentials. Finally, we consider two nontrivial applications of the p-wave pseudopotential: we solve analytically the problem of two interacting spin-polarized fermions confined in a harmonic trap, and we analyze the scattering of p-wave interacting particles in a quasi-two-dimensional system.

  2. Overall coherence and coherent-mode expansion of spectrally partially coherent plane-wave pulses.

    PubMed

    Lajunen, Hanna; Tervo, Jani; Vahimaa, Pasi

    2004-11-01

    The modal theory for spectrally partially coherent nonstationary plane waves is introduced. The theory is first developed in the space-frequency domain and then extended to the space-time domain. Propagation properties of the coherent modes are analyzed. The concept of the overall degree of coherence is extended to the domain of nonstationary fields, and it is shown that the overall degree of coherence of partially coherent plane-wave pulses is the same in the space-frequency and space-time domains. The theory is applied to the recently introduced concept of spectrally Gaussian Schell-model plane-wave pulses.

  3. Overall coherence and coherent-mode expansion of spectrally partially coherent plane-wave pulses

    NASA Astrophysics Data System (ADS)

    Lajunen, Hanna; Tervo, Jani; Vahimaa, Pasi

    2004-11-01

    The modal theory for spectrally partially coherent nonstationary plane waves is introduced. The theory is first developed in the space-frequency domain and then extended to the space-time domain. Propagation properties of the coherent modes are analyzed. The concept of the overall degree of coherence is extended to the domain of nonstationary fields, and it is shown that the overall degree of coherence of partially coherent plane-wave pulses is the same in the space-frequency and space-time domains. The theory is applied to the recently introduced concept of spectrally Gaussian Schell-model plane-wave pulses.

  4. Plane-wave analysis of solar acoustic-gravity waves: A (slightly) new approach

    NASA Technical Reports Server (NTRS)

    Bogart, Richard S.; Sa, L. A. D.; Duvall, Thomas L., Jr.; Haber, Deborah A.; Toomre, Juri; Hill, Frank

    1995-01-01

    The plane-wave decomposition of the acoustic-gravity wave effects observed in the photosphere provides a computationally efficient technique that probes the structure of the upper convective zone and boundary. In this region, the flat sun approximation is considered as being reasonably accurate. A technique to be used for the systematic plane-wave analysis of Michelson Doppler imager data, as part of the solar oscillations investigation, is described. Estimates of sensitivity are presented, and the effects of using different planar mappings are discussed. The technique is compared with previous approaches to the three dimensional plane-wave problem.

  5. Fraunhofer diffraction of the plane wave by a multilevel (quantized) spiral phase plate.

    PubMed

    Kotlyar, Victor V; Kovalev, Alexey A

    2008-01-15

    We obtain an analytical expression in the form of a finite sum of plane waves that describes the paraxial scalar Fraunhofer diffraction of a limited plane wave by a multilevel (quantized) spiral phase plate (SPP) bounded by a polygonal aperture. For several topological charges of the SPP we numerically obtain the minimal number of SPP sectors for which the RMS between the Fraunhofer diffraction patterns for multilevel and continuous SPP does not exceed 2%.

  6. Analysis for the convergence problem of the plane-wave expansion method for photonic crystals.

    PubMed

    Shen, Linfang; He, Sailing

    2002-05-01

    The convergence feature of two types of plane-wave expansion methods commonly used for photonic crystals is analyzed. It is shown that the reason for the slow convergence of these plane-wave expansion methods is not the slow convergence of the Fourier series for the permittivity profile of the photonic crystal but the inappropriate formulation of the eigenproblem. A new formulation of the eigenproblem is presented to improve the convergence in the one-dimensional case.

  7. Properties of the transformation from the spherical wave expansion to the plane wave expansion

    NASA Astrophysics Data System (ADS)

    Cappellin, Cecilia; Breinbjerg, Olav; Frandsen, Aksel

    2008-02-01

    The transformation between the spherical wave expansion (SWE) and the plane wave expansion (PWE) is investigated with respect to a range of its fundamental properties. First, the transformation of individual spherical waves is studied in order to understand how these contribute to the different regions of the plane wave spectrum. Second, the number of spherical waves necessary to accurately determine the PWE over different regions of the spectral domain is investigated. Third, numerical aspects of the transformation are addressed.

  8. Tails of plane wave spacetimes: Wave-wave scattering in general relativity

    NASA Astrophysics Data System (ADS)

    Harte, Abraham I.

    2013-10-01

    One of the most important characteristics of light in flat spacetime is that it satisfies Huygens’ principle: Initial data for the vacuum Maxwell equations evolve sharply along null (and not timelike) geodesics. In flat spacetime, there are no tails which linger behind expanding wavefronts. Tails generically do exist, however, if the background spacetime is curved. The only nonflat vacuum geometries where electromagnetic fields satisfy Huygens’ principle are known to be those associated with gravitational plane waves. This paper investigates whether perturbations to the plane wave geometry itself also propagate without tails. First-order perturbations to all locally constructed curvature scalars are indeed found to satisfy Huygens’ principles. Despite this, gravitational tails do exist. Locally, they can only perturb one plane wave spacetime into another plane wave spacetime. A weak localized beam of gravitational radiation passing through an arbitrarily strong plane wave therefore leaves behind only a slight perturbation to the waveform of the background plane wave. The planar symmetry of that wave cannot be disturbed by any linear tail. These results are obtained by first deriving the retarded Green function for Lorenz-gauge metric perturbations and then analyzing its consequences for generic initial-value problems.

  9. Benchmarking the pseudopotential and fixed-node approximations in diffusion Monte Carlo calculations of molecules and solids

    DOE PAGES

    Nazarov, Roman; Shulenburger, Luke; Morales, Miguel A.; Hood, Randolph Q.

    2016-03-28

    Diffusion Monte Carlo (DMC) calculations of the spectroscopic properties of a large set of molecules were performed, assessing the effect of different approximations. In systems containing elements with large atomic numbers, we show that the errors associated with the use of nonlocal mean-field-based pseudopotentials in DMC calculations can be significant and may surpass the fixed-node error. We suggest practical guidelines for reducing these pseudopotential errors, which allow us to obtain DMC-computed spectroscopic parameters of molecules and equation of state properties of solids in excellent agreement with experiment.

  10. Variational solution of Poisson's equation using plane waves in adaptive coordinates.

    PubMed

    Pérez-Jordá, José M

    2014-11-01

    A procedure for solving Poisson's equation using plane waves in adaptive coordinates (u) is described. The method, based on Gygi's work, writes a trial potential ξ as the product of a preselected Coulomb weight μ times a plane-wave expansion depending on u. Then, the Coulomb potential generated by a given density ρ is obtained by variationally optimizing ξ, so that the error in the Coulomb energy is second-order with respect to the error in ξ. The Coulomb weight μ is chosen to provide to each ξ the typical long-range tail of a Coulomb potential, so that calculations on atoms and molecules are made possible without having to resort to the supercell approximation. As a proof of concept, the method is tested on the helium atom and the H_{2} and H_{3}^{+} molecules, where Hartree-Fock energies with better than milli-Hartree accuracy require only a moderate number of plane waves.

  11. Ultrasonic elastic modes in solid bars: an application of the plane wave expansion method.

    PubMed

    Manzanares-Martinez, Betsabe; Ramos-Mendieta, Felipe; Baltazar, Arturo

    2010-06-01

    Ultrasonic elastic modes in solid bars are investigated theoretically and experimentally using the plane wave expansion method to calculate the dispersion curves k=k(omega) for longitudinal, torsional, and flexural waves. The plane wave extension method allows to consider rods of circular and square cross sections. The technique, which has received attention in the study of photonic and phononic crystals, is adapted in order to identify the various types of modes. Results are compared with predictions from semi-analytical models. The numerical approximation is validated with the experimental determination of the time-frequency dispersion curves. The technique based on the plane wave expansion method presented here could be a numerical alternative used to determine the wave propagation and modal vibration with high precision in structures like bars and cylinders. Practical applications of this study could include the inspection of long-span engineering systems with bar or cylinder like characteristics.

  12. PlaneWave Admittance Method- a novel approach for determining the electromagnetic modes in photonic structures.

    PubMed

    Dems, Maciej; Kotynski, Rafal; Panajotov, Krassimir

    2005-05-01

    In this article we present a novel approach for determining the electromagnetic modes of photonic multilayer structures. We combine the plane wave expansion method with the method of lines resulting in a fast and accurate computational technique which we named the plane wave admittance method. In addition, we incorporate perfectly matched layers at the boundaries parallel to the multilayer surfaces which allow for easy determination of leaky modes. The convergence of the method is verified for the case of photonic crystal slab showing very good agreement with the results obtained with full three-dimensional plane wave expansion method while the numerical effort is largely reduced. The numerical implementation of the method will be soon available on the web.

  13. Modeling bulk and surface Pt using the "Gaussian and plane wave" density functional theory formalism: validation and comparison to k-point plane wave calculations.

    PubMed

    Santarossa, Gianluca; Vargas, Angelo; Iannuzzi, Marcella; Pignedoli, Carlo A; Passerone, Daniele; Baiker, Alfons

    2008-12-21

    We present a study on structural and electronic properties of bulk platinum and the two surfaces (111) and (100) comparing the Gaussian and plane wave method to standard plane wave schemes, normally employed for density functional theory calculations on metallic systems. The aim of this investigation is the assessment of methods based on the expansion of the Kohn-Sham orbitals into localized basis sets and on the supercell approach, in the description of the metallicity of Pt. Electronic structure calculations performed at Gamma-point only on supercells of different sizes, from 108 up to 864 atoms, are compared to the results obtained for the unit cell of four Pt atoms where the k-point expansion of the wave function over Monkhorst-Pack grids up to (10x10x10) has been employed. The evaluation of the two approaches with respect to bulk properties is done through the calculation of the equilibrium lattice constant, the bulk modulus, and the total and the d-projected density of states. For the Pt(111) and Pt(100) surfaces, we consider the relaxation of the first layers, the surface energies, the work function, the total density of states, as well as the center and filling of the d bands. Our results confirm that the accuracy of two approaches in the description of electronic and structural properties of Pt is equivalent, providing that consistent supercells and k-point meshes are used. Moreover, we estimate the supercell size that can be safely adopted in the Gaussian and plane wave method in order to obtain the same reliability of previous theoretical studies based on well converged plane wave calculations available in literature. The latter studies, in turn, set the level of agreement with experimental data. In particular, we obtain excellent agreement in the evaluation of the density of states for either bulk and surface systems, and our data are also in good agreement with previous works on Pt reported in literature. We conclude that Gaussian and plane wave

  14. Vectorial spherical-harmonics representation of an inhomogeneous elliptically polarized plane wave.

    PubMed

    Frezza, F; Mangini, F

    2015-07-01

    In this paper, a generalization of the vectorial spherical-harmonics expansion of an inhomogeneous elliptically polarized plane wave is presented. The solution has been achieved using the Legendre functions generalized via hypergeometric and gamma functions, shifting the difficulty to the determination of only expansion coefficients. In order to validate the presented method, a Matlab code has been implemented. To compare the results a Mie scattering by a sphere is considered, then a truncation criterion for the numerical evaluation of the series is proposed, and the Mie scattering coefficients by perfectly conducting and dielectric spheres excited by an inhomogeneous elliptically polarized plane wave are shown. PMID:26367169

  15. Population analysis of plane-wave electronic structure calculations of bulk materials

    SciTech Connect

    Segall, M.D.; Shah, R.; Pickard, C.J.; Payne, M.C.

    1996-12-01

    {ital Ab} {ital initio} plane-wave electronic structure calculations are widely used in the study of bulk materials. A technique for the projection of plane-wave states onto a localized basis set is used to calculate atomic charges and bond populations by means of Mulliken analysis. We analyze a number of simple bulk crystals and find correlations of overlap population with covalency of bonding and bond strength, and effective valence charge with ionicity of bonding. Thus, we show that the techniques described in this paper may be usefully applied in the field of solid state physics. {copyright}{ital 1996 The American Physical Society.}

  16. Vectorial spherical-harmonics representation of an inhomogeneous elliptically polarized plane wave.

    PubMed

    Frezza, F; Mangini, F

    2015-07-01

    In this paper, a generalization of the vectorial spherical-harmonics expansion of an inhomogeneous elliptically polarized plane wave is presented. The solution has been achieved using the Legendre functions generalized via hypergeometric and gamma functions, shifting the difficulty to the determination of only expansion coefficients. In order to validate the presented method, a Matlab code has been implemented. To compare the results a Mie scattering by a sphere is considered, then a truncation criterion for the numerical evaluation of the series is proposed, and the Mie scattering coefficients by perfectly conducting and dielectric spheres excited by an inhomogeneous elliptically polarized plane wave are shown.

  17. Electronic excitation spectra from time-dependent density functional response theory using plane-wave methods

    NASA Astrophysics Data System (ADS)

    Doltsinis, Nikos L.; Sprik, Michiel

    2000-11-01

    The time-dependent density functional response theory method for the computation of electronic excitation spectra has been implemented in a plane-wave basis set/pseudo-potential formalism. We compare our test results for N2 and H2CO to literature atomic basis set calculations and find good agreement. We also discuss some of the technical complications specific to the use of plane-wave basis sets. As an application, the thermally broadened photoabsorption spectrum of formamide at room temperature is computed by averaging over a number of vibrational configurations sampled from an ab initio molecular dynamics run and compared to experiment.

  18. The Relativistic Transformation for an Electromagnetic Plane Wave with General Time Dependence

    ERIC Educational Resources Information Center

    Smith, Glenn S.

    2012-01-01

    In special relativity, the transformation between inertial frames for an electromagnetic plane wave is usually derived for the time-harmonic case (the field is a sinusoid of infinite duration), even though all practical waves are of finite duration and may not even contain a dominant sinusoid. This paper presents an alternative derivation in which…

  19. Vector-based plane-wave spectrum method for the propagation of cylindrical electromagnetic fields.

    PubMed

    Shi, S; Prather, D W

    1999-11-01

    We present a vector-based plane-wave spectrum (VPWS) method for efficient propagation of cylindrical electromagnetic fields. In comparison with electromagnetic propagation integrals, the VPWS method significantly reduces time of propagation. Numerical results that illustrate the utility of this method are presented.

  20. A beamforming method for plane wave Doppler imaging of high flow velocities

    NASA Astrophysics Data System (ADS)

    Mansour, Omar; Poepping, Tamie L.; Lacefield, James C.

    2016-04-01

    Plane wave imaging is desirable for its ability to achieve high frame rates, allowing the capture of fast dynamic events, and continuous Doppler data. In most implementations of plane-wave imaging, multiple low resolution image (LRI) frames from different plane wave tilt angles are compounded to form a single high resolution image (HRI) frame, thereby reducing the frame rate. Compounding is a low-pass mean filter that causes attenuation and aliasing to signals with high Doppler shifts. On the other hand, the lateral beam profile and hence the quality of the HRI frames is improved by increasing the number of compounded frames. Therefore, a tradeoff exists between the Doppler limits and beam profile. In this paper, we present a method that eliminates this tradeoff and produces high resolution images without the use of compounding. The method suppresses the off-focus (clutter) signal by spreading its spectrum, while keeping the spectrum of the in-focus signal intact. The spreading is achieved by using a random sequence of tilt angles, as opposed to a linear sweep. Experiments performed using a carotid vessel phantom with constant flow demonstrate that the spread-spectrum method more accurately measures the parabolic flow profile of the vessel and in particular outperforms conventional plane-wave Doppler at higher flow velocities. The spread-spectrum method is expected to be valuable for Doppler applications that require measurement of high velocities at high frame rates.

  1. Non-one-dimensional self-similar solutions with plane waves in gas dynamics

    NASA Astrophysics Data System (ADS)

    Poslavskii, S. A.; Shikin, I. S.

    1986-02-01

    A set of new exact self-similar solutions describing the non-one-dimensional adiabatic motions of an ideal gas with plane waves is presented. The solutions include homogeneous gas expansion in planes perpendicular to the direction of the principal motion. It is shown that for such solutions, the system of gasdynamic equations is reduced to a system of ordinary differental equations.

  2. The use of the plane wave fluid-structure interaction loading approximation in NASTRAN

    NASA Technical Reports Server (NTRS)

    Dawson, R. L.

    1991-01-01

    The Plane Wave Approximation (PWA) is widely used in finite element analysis to implement the loading generated by an underwater shock wave. The method required to implement the PWA in NASTRAN is presented along with example problems. A theoretical background is provided and the limitations of the PWA are discussed.

  3. Time-dependent plane-wave spectrum representations for radiation from volume source distributions

    NASA Astrophysics Data System (ADS)

    Heyman, Ehud

    1996-02-01

    A new time-domain spectral theory for radiation from a time-dependent source distribution, is presented. The full spectral representation is based on a Radon transform of the source distribution in the four-dimensional space-time domain and consists of time-dependent plane waves that propagate in all space directions and with all (spectral) propagation speeds vκ. This operation, termed the slant stack transform, involves projection of the time-dependent source distribution along planes normal to the spectral propagation direction and stacking them with a progressive delay corresponding to the spectral propagation speed vκ along this direction. Outside the source domain, this three-fold representation may be contracted into a two-fold representation consisting of time-dependent plane waves that satisfy the spectral constraint vκ=c with c being the medium velocity. In the two-fold representation, however, the complete spectral representation involves both propagating time-dependent plane waves and evanescent time-dependent plane waves. We explore the separate role of these spectral constituents in establishing the causal field, and determine the space-time regions where the field is described only by the propagating spectrum. The spectral theory is presented here for scalar wave fields, but it may readily be extended to vector electromagnetic fields.

  4. Plane-wave-spectrum approach for calculations of radiation pattern of junction lasers

    SciTech Connect

    Sen, T.K.; Datta, A.K.; Basuray, A.

    1986-02-01

    An analytical expression for mode-conversion coefficients at a laser-air interface is derived using plane-wave decomposition of the modal fields. Both the mode-conversion coefficients and the radiation pattern are explicitly expressed as function of Fresnel reflection coefficients of the interface and the incident mode spectrum.

  5. Ray invariants, plane wave spectra, and adiabatic modes for tapered dielectric waveguides

    NASA Astrophysics Data System (ADS)

    Arnold, J. M.; Felsen, L. B.

    1984-10-01

    In nonseparable problems resulting from the analysis of wave propagation in longitudinally varying waveguides, such as a wedge-shaped taper, singularities appear in both ray and coupled mode treatments at the local normal mode cutoff transition. A uniformization of the local normal (adiabatic) mode is proposed, using plane wave spectra, which effectively resolves this difficulty.

  6. From plane waves to local Gaussians for the simulation of correlated periodic systems

    NASA Astrophysics Data System (ADS)

    Booth, George H.; Tsatsoulis, Theodoros; Chan, Garnet Kin-Lic; Grüneis, Andreas

    2016-08-01

    We present a simple, robust, and black-box approach to the implementation and use of local, periodic, atom-centered Gaussian basis functions within a plane wave code, in a computationally efficient manner. The procedure outlined is based on the representation of the Gaussians within a finite bandwidth by their underlying plane wave coefficients. The core region is handled within the projected augment wave framework, by pseudizing the Gaussian functions within a cutoff radius around each nucleus, smoothing the functions so that they are faithfully represented by a plane wave basis with only moderate kinetic energy cutoff. To mitigate the effects of the basis set superposition error and incompleteness at the mean-field level introduced by the Gaussian basis, we also propose a hybrid approach, whereby the complete occupied space is first converged within a large plane wave basis, and the Gaussian basis used to construct a complementary virtual space for the application of correlated methods. We demonstrate that these pseudized Gaussians yield compact and systematically improvable spaces with an accuracy comparable to their non-pseudized Gaussian counterparts. A key advantage of the described method is its ability to efficiently capture and describe electronic correlation effects of weakly bound and low-dimensional systems, where plane waves are not sufficiently compact or able to be truncated without unphysical artifacts. We investigate the accuracy of the pseudized Gaussians for the water dimer interaction, neon solid, and water adsorption on a LiH surface, at the level of second-order Møller-Plesset perturbation theory.

  7. From plane waves to local Gaussians for the simulation of correlated periodic systems.

    PubMed

    Booth, George H; Tsatsoulis, Theodoros; Chan, Garnet Kin-Lic; Grüneis, Andreas

    2016-08-28

    We present a simple, robust, and black-box approach to the implementation and use of local, periodic, atom-centered Gaussian basis functions within a plane wave code, in a computationally efficient manner. The procedure outlined is based on the representation of the Gaussians within a finite bandwidth by their underlying plane wave coefficients. The core region is handled within the projected augment wave framework, by pseudizing the Gaussian functions within a cutoff radius around each nucleus, smoothing the functions so that they are faithfully represented by a plane wave basis with only moderate kinetic energy cutoff. To mitigate the effects of the basis set superposition error and incompleteness at the mean-field level introduced by the Gaussian basis, we also propose a hybrid approach, whereby the complete occupied space is first converged within a large plane wave basis, and the Gaussian basis used to construct a complementary virtual space for the application of correlated methods. We demonstrate that these pseudized Gaussians yield compact and systematically improvable spaces with an accuracy comparable to their non-pseudized Gaussian counterparts. A key advantage of the described method is its ability to efficiently capture and describe electronic correlation effects of weakly bound and low-dimensional systems, where plane waves are not sufficiently compact or able to be truncated without unphysical artifacts. We investigate the accuracy of the pseudized Gaussians for the water dimer interaction, neon solid, and water adsorption on a LiH surface, at the level of second-order Møller-Plesset perturbation theory.

  8. From plane waves to local Gaussians for the simulation of correlated periodic systems.

    PubMed

    Booth, George H; Tsatsoulis, Theodoros; Chan, Garnet Kin-Lic; Grüneis, Andreas

    2016-08-28

    We present a simple, robust, and black-box approach to the implementation and use of local, periodic, atom-centered Gaussian basis functions within a plane wave code, in a computationally efficient manner. The procedure outlined is based on the representation of the Gaussians within a finite bandwidth by their underlying plane wave coefficients. The core region is handled within the projected augment wave framework, by pseudizing the Gaussian functions within a cutoff radius around each nucleus, smoothing the functions so that they are faithfully represented by a plane wave basis with only moderate kinetic energy cutoff. To mitigate the effects of the basis set superposition error and incompleteness at the mean-field level introduced by the Gaussian basis, we also propose a hybrid approach, whereby the complete occupied space is first converged within a large plane wave basis, and the Gaussian basis used to construct a complementary virtual space for the application of correlated methods. We demonstrate that these pseudized Gaussians yield compact and systematically improvable spaces with an accuracy comparable to their non-pseudized Gaussian counterparts. A key advantage of the described method is its ability to efficiently capture and describe electronic correlation effects of weakly bound and low-dimensional systems, where plane waves are not sufficiently compact or able to be truncated without unphysical artifacts. We investigate the accuracy of the pseudized Gaussians for the water dimer interaction, neon solid, and water adsorption on a LiH surface, at the level of second-order Møller-Plesset perturbation theory. PMID:27586908

  9. The Exact Formula for an Energy Band Spectrum Gradient within the New Completely Orthogonalized Plane Wave Method

    NASA Astrophysics Data System (ADS)

    Syrotyuk, S. V.; Kynash, Yu. E.; Sobchuk, I. S.

    1997-03-01

    The formula for calculating the spectrum gradient gk = gradk E(k) at an arbitrary point k in the Brillouin zone has been derived on the basis of the new completely orthogonalized plane wave formalism (COPW). This important physical quantity has been obtained within the COPW basis for the first time. It displays a true plane wave basis limit.

  10. Pseudopotentials for Excited States of Hydrogen: A Vivid Illustration of Limitations to the Use of Pseudopotential Results.

    ERIC Educational Resources Information Center

    Goodfriend, P. L.

    1979-01-01

    It is shown that exact pseudopotentials for excited states of hydrogen atoms can be derived. A very simple, novel application of pseudopotential method which displays vividly some of its limitations is presented. (Author/GA)

  11. Scalable fine-grained parallelization of plane-wave-based ab initio molecular dynamics for large supercomputers.

    PubMed

    Vadali, Ramkumar V; Shi, Yan; Kumar, Sameer; Kale, Laxmikant V; Tuckerman, Mark E; Martyna, Glenn J

    2004-12-01

    Many systems of great importance in material science, chemistry, solid-state physics, and biophysics require forces generated from an electronic structure calculation, as opposed to an empirically derived force law to describe their properties adequately. The use of such forces as input to Newton's equations of motion forms the basis of the ab initio molecular dynamics method, which is able to treat the dynamics of chemical bond-breaking and -forming events. However, a very large number of electronic structure calculations must be performed to compute an ab initio molecular dynamics trajectory, making the efficiency as well as the accuracy of the electronic structure representation critical issues. One efficient and accurate electronic structure method is the generalized gradient approximation to the Kohn-Sham density functional theory implemented using a plane-wave basis set and atomic pseudopotentials. The marriage of the gradient-corrected density functional approach with molecular dynamics, as pioneered by Car and Parrinello (R. Car and M. Parrinello, Phys Rev Lett 1985, 55, 2471), has been demonstrated to be capable of elucidating the atomic scale structure and dynamics underlying many complex systems at finite temperature. However, despite the relative efficiency of this approach, it has not been possible to obtain parallel scaling of the technique beyond several hundred processors on moderately sized systems using standard approaches. Consequently, the time scales that can be accessed and the degree of phase space sampling are severely limited. To take advantage of next generation computer platforms with thousands of processors such as IBM's BlueGene, a novel scalable parallelization strategy for Car-Parrinello molecular dynamics is developed using the concept of processor virtualization as embodied by the Charm++ parallel programming system. Charm++ allows the diverse elements of a Car-Parrinello molecular dynamics calculation to be interleaved with low

  12. Plane-wave density functional theory investigation of adsorption of 2,4,6-trinitrotoluene on Al-hydroxylated (0001) surface of (4 × 4) α-alumina.

    PubMed

    Shukla, Manoj K; Hill, Frances

    2014-10-15

    This article reports the results of the theoretical investigation of adsorption of 2,4,6-trinitrotoluene (TNT) on Al-hydroxylated (0001) surface of (4 × 4) α-alumina (α-Al2O3) using plane-wave Density Functional Theory. Sixteen water molecules were used to hydroxylate the alumina surface. The Perdew-Burke-Ernzerhof functional and the recently developed van der Waals functional (vdW-DF2) were used. The interaction of electron with core was accounted using the Vanderbilt ultrasoft pseudopotentials. It was found that hydroxylation has significant influence on the geometry of alumina and such changes are prominent up to few layers from the surface. Particularly, due to the Al-hydroxylation the oxygen layers are decomposed into sublayers and such partitioning becomes progressively weaker for interior layers. Moreover, the nature of TNT adsorption interaction is changed from covalent type on the pristine alumina surface to hydrogen-bonding interaction on the Al-hydroxylated alumina surface. TNT in parallel orientation forms several hydrogen bonds compared to that in the perpendicular orientation with hydroxyl groups of the Al-hydroxylated alumina surface. Therefore, the parallel orientation will be present in the adsorption of TNT on Al-hydroxylated (0001) surface of α-alumina. Further, the vdW-DF2 van der Waals functional was found to be most suitable and should be used for such surface adsorption investigation.

  13. Comparison of finite source and plane wave scattering from corrugated surfaces

    NASA Technical Reports Server (NTRS)

    Levine, D. M.

    1977-01-01

    The choice of a plane wave to represent incident radiation in the analysis of scatter from corrugated surfaces was examined. The physical optics solution obtained for the scattered fields due to an incident plane wave was compared with the solution obtained when the incident radiation is produced by a source of finite size and finite distance from the surface. The two solutions are equivalent if the observer is in the far field of the scatterer and the distance from observer to scatterer is large compared to the radius of curvature at the scatter points, condition not easily satisfied with extended scatterers such as rough surfaces. In general, the two solutions have essential differences such as in the location of the scatter points and the dependence of the scattered fields on the surface properties. The implication of these differences to the definition of a meaningful radar cross section was examined.

  14. Acoustic plane waves incident on an oblique clamped panel in a rectangular duct

    NASA Technical Reports Server (NTRS)

    Unz, H.; Roskam, J.

    1980-01-01

    The theory of acoustic plane waves incident on an oblique clamped panel in a rectangular duct was developed from basic theoretical concepts. The coupling theory between the elastic vibrations of the panel (plate) and the oblique incident acoustic plane wave in infinite space was considered in detail, and was used for the oblique clamped panel in the rectangular duct. The partial differential equation which governs the vibrations of the clamped panel (plate) was modified by adding to it stiffness (spring) forces and damping forces. The Transmission Loss coefficient and the Noise Reduction coefficient for oblique incidence were defined and derived in detail. The resonance frequencies excited by the free vibrations of the oblique finite clamped panel (plate) were derived and calculated in detail for the present case.

  15. Analysis of surface modes in photonic crystals by a plane-wave transfer-matrix method.

    PubMed

    Che, Ming; Li, Zhi-Yuan

    2008-09-01

    We have developed a plane-wave transfer-matrix method (PWTMM) with the aid of the interpolation technique to analyze the dispersion relation of surface modes in photonic crystal or photonic crystal surface waveguide. The proposed approach has been applied to several surface structures in two-dimensional photonic crystals. The calculated dispersion relation of the surface modes is in good agreement with the result obtained by the conventional plane-wave expansion method in combination with the supercell technique. The developed PWTMM needs to handle only a single unit-cell layer domain and is therefore numerically friendly. The proposed approach can become an efficient and accurate numerical tool to understand and design surface modes in different two-dimensional and three-dimensional photonic crystals with complex geometries.

  16. Photonic band structures solved by a plane-wave-based transfer-matrix method.

    PubMed

    Li, Zhi-Yuan; Lin, Lan-Lan

    2003-04-01

    Transfer-matrix methods adopting a plane-wave basis have been routinely used to calculate the scattering of electromagnetic waves by general multilayer gratings and photonic crystal slabs. In this paper we show that this technique, when combined with Bloch's theorem, can be extended to solve the photonic band structure for 2D and 3D photonic crystal structures. Three different eigensolution schemes to solve the traditional band diagrams along high-symmetry lines in the first Brillouin zone of the crystal are discussed. Optimal rules for the Fourier expansion over the dielectric function and electromagnetic fields with discontinuities occurring at the boundary of different material domains have been employed to accelerate the convergence of numerical computation. Application of this method to an important class of 3D layer-by-layer photonic crystals reveals the superior convergency of this different approach over the conventional plane-wave expansion method.

  17. Extracting the spectral function of 4He from a relativistic plane-wave treatment

    NASA Astrophysics Data System (ADS)

    Abu-Raddad, L. J.; Piekarewicz, J.

    2001-12-01

    The spectral function of 4He is extracted from a plane-wave approximation to the (e,e'p) reaction using a fully relativistic formalism. We take advantage of both an algebraic ``trick'' and a general relativistic formalism for quasifree processes developed earlier to arrive at transparent, analytical expressions for all quasifree (e,e'p) observables. An observable is identified for the clean and model-independent extraction of the spectral function. Our simple relativistic plane-wave calculations provide baseline predictions for the recently measured, but not yet fully analyzed, momentum distribution of 4He by the A1 Collaboration from Mainz. Yet in spite of its simplicity, our approach predicts momentum distributions for 4He that rival some of the best nonrelativistic calculations to date. Finally, we highlight some of the challenges and opportunities that remain, both theoretically and experimentally, in the extraction of quasifree observables.

  18. Extracting the spectral function of He-4 from a relativistic plane-wave treatment

    NASA Astrophysics Data System (ADS)

    Abu-Raddad, Laith; Piekarewicz, Jorge

    2001-10-01

    The spectral function of He-4 is extracted from a plane-wave approximation to the (e,e'p) reaction using a fully relativistic formalism. We take advantage of both an algebraic ``trick'' and a general relativistic formalism for quasifree processes developed earlier to arrive at transparent, analytical expressions for all quasifree (e,e'p) observables. An observable is identified for the clean and model-independent extraction of the spectral function. Our simple relativistic plane-wave calculations provide baseline predictions for the recently measured, but not yet fully analyzed, momentum distribution of He-4 by the A1-collaboration from Mainz. Yet in spite of its simplicity, our approach predicts momentum distributions for He-4 that rival some of the best nonrelativistic calculations to date. Finally, we highlight some of the challenges and opportunities that remain, both theoretically and experimentally, in the extraction of quasifree observables.

  19. High-Frequency Coupling to Cables for Plane Wave and Random Wave Conditions

    NASA Astrophysics Data System (ADS)

    Pissoort, D.; Vanhee, F.; Boesman, B.; Catrysse, J.; Vandenbosch, G.; Gielen, G.

    2012-05-01

    In this paper, the high-frequency coupling from electromagnetic fields to cables is studied and this under (i) plane-wave conditions representing a susceptibility test in a semi-anechoic room and (ii) random wave conditions representing a more realistic environment with many reflections. Two set-ups are considered. First, a s imple wire above an infinite ground plane. Second, a more realistic set-up representing a desktop device with attached cables whose layout is according to EN 55016-2-3:2006 [1]. It is shown that for frequencies above 1 GHz the induced (worst-case) current at the side of the device under test can differ significantly between plane-wave and random wave conditions. Moreover, the random wave condition does necessarily not lead to the highest induced currents.

  20. Scattering from cylinders using the two-dimensional vector plane wave spectrum: addendum.

    PubMed

    Pawliuk, Peter; Yedlin, Matthew

    2012-03-01

    The solution for the vector plane wave spectrum scattering from multiple cylinders by Pawliuk and Yedlin [J. Opt. Soc. A28, 1177 (2011)] only provided the single scattering coefficients for the TM polarization case. The TE solution is similar except for the form of the single scattering coefficients. Here we describe the single scattering coefficients for both polarizations and three types of cylinders: dielectrics, perfect electric conductors, and perfect magnetic conductors.

  1. Plane Wave Diffraction by a Finite Plate with Impedance Boundary Conditions

    PubMed Central

    Nawaz, Rab; Ayub, Muhammad; Javaid, Akmal

    2014-01-01

    In this study we have examined a plane wave diffraction problem by a finite plate having different impedance boundaries. The Fourier transforms were used to reduce the governing problem into simultaneous Wiener-Hopf equations which are then solved using the standard Wiener-Hopf procedure. Afterwards the separated and interacted fields were developed asymptotically by using inverse Fourier transform and the modified stationary phase method. Detailed graphical analysis was also made for various physical parameters we were interested in. PMID:24755624

  2. A nonperturbative definition of N = 4 Super Yang-Mills by the plane wave matrix model

    SciTech Connect

    Shimasaki, Shinji

    2008-11-23

    We propose a nonperturbative definition of N = 4 Super Yang-Mills(SYM). We realize N = 4 SYM on RxS{sup 3} as the theory around a vacuum of the plane wave matrix model. Our regularization preserves 16 supersymmetries and the gauge symmetry. We perform the one-loop calculation to give evidence that in the continuum limit the superconformal symmetry is restored.

  3. Description of arbitrary shaped beams in elliptical cylinder coordinates, by using a plane wave spectrum approach

    NASA Astrophysics Data System (ADS)

    Gouesbet, Gérard; Mees, Loic; Gréhan, Gérard; Ren, Kuan Fang

    1999-03-01

    The description of arbitrary shaped beams in elliptical cylinder coordinates is presented by using a plane wave spectrum approach. It is demonstrated and exemplified that this approach is equivalent to a formally more rigorous approach in terms of distributions. Beam shape coefficients are evaluated by using quadratures. The behavior of these quadratures is discussed in the case of a first-order Davis beam which does not exactly satisfy Maxwell's equations.

  4. Spectral responses of gyrotropic chiral sculptured thin films to obliquely incident plane waves

    NASA Astrophysics Data System (ADS)

    Pickett, Matthew D.; Lakhtakia, Akhlesh; Polo, John A., Jr.

    Gyrotropic chiral sculptured thin films (STFs) exhibit optical activity due to their structural chirality, local anisotropy, and magneto-optic gyrotropy. We adapted two algorithms for nongyrotopic chiral STFs to investigate the circular-polarization-sensitivity of gyrotropic chiral STFs to incident plane waves. The impacts of gyrotropy and oblique angles of incidence on the reflectances and the transmittances were examined, and several conclusions drawn. In particular, we found that the incorporation of gyrotropy results in a blueshift of the Bragg regime.

  5. Radiated Susceptibility of a Twisted-Wire Pair Illuminated by a Random Plane-Wave Spectrum

    NASA Astrophysics Data System (ADS)

    Spadacini, Giordano; Pignari, Sergio A.

    This work presents a statistical model for the radiated susceptibility (RS) of an unshielded twisted-wire pair (TWP) running above ground, illuminated by a random electromagnetic field. The incident field is modeled as a superposition of elemental plane waves with random angular density, phase, and polarization. The statistical properties of both the differential-mode (DM) and the common-mode (CM) noise voltages induced across the terminal loads are derived and discussed.

  6. On the use of evanescent plane waves for low-frequency energy transmission across material interfaces.

    PubMed

    Woods, Daniel C; Bolton, J Stuart; Rhoads, Jeffrey F

    2015-10-01

    The transmission of airborne sound into high-impedance media is of interest in several applications. For example, sonic booms in the atmosphere may impact marine life when incident on the ocean surface, or affect the integrity of existing structures when incident on the ground. Transmission across high impedance-difference interfaces is generally limited by reflection and refraction at the surface, and by the critical angle criterion. However, spatially decaying incident waves, i.e., inhomogeneous or evanescent plane waves, may transmit energy above the critical angle, unlike homogeneous plane waves. The introduction of a decaying component to the incident trace wavenumber creates a nonzero propagating component of the transmitted normal wavenumber, so energy can be transmitted across the interface. A model of evanescent plane waves and their transmission across fluid-fluid and fluid-solid interfaces is developed here. Results are presented for both air-water and air-solid interfaces. The effects of the incident wave parameters (including the frequency, decay rate, and incidence angle) and the interfacial properties are investigated. Conditions for which there is no reflection at the air-solid interface, due to impedance matching between the incident and transmitted waves, are also considered and are found to yield substantial transmission increases over homogeneous incident waves. PMID:26520290

  7. On the use of evanescent plane waves for low-frequency energy transmission across material interfaces.

    PubMed

    Woods, Daniel C; Bolton, J Stuart; Rhoads, Jeffrey F

    2015-10-01

    The transmission of airborne sound into high-impedance media is of interest in several applications. For example, sonic booms in the atmosphere may impact marine life when incident on the ocean surface, or affect the integrity of existing structures when incident on the ground. Transmission across high impedance-difference interfaces is generally limited by reflection and refraction at the surface, and by the critical angle criterion. However, spatially decaying incident waves, i.e., inhomogeneous or evanescent plane waves, may transmit energy above the critical angle, unlike homogeneous plane waves. The introduction of a decaying component to the incident trace wavenumber creates a nonzero propagating component of the transmitted normal wavenumber, so energy can be transmitted across the interface. A model of evanescent plane waves and their transmission across fluid-fluid and fluid-solid interfaces is developed here. Results are presented for both air-water and air-solid interfaces. The effects of the incident wave parameters (including the frequency, decay rate, and incidence angle) and the interfacial properties are investigated. Conditions for which there is no reflection at the air-solid interface, due to impedance matching between the incident and transmitted waves, are also considered and are found to yield substantial transmission increases over homogeneous incident waves.

  8. A plane wave generation method by wave number domain point focusing.

    PubMed

    Chang, Ji-Ho; Choi, Jung-Woo; Kim, Yang-Hann

    2010-11-01

    A method for generation of a wave-field that is a plane wave is described. This method uses an array of loudspeakers phased so that the field in the wave-number domain is nearly concentrated at a point, this point being at the wave-number vector of the desired plane wave. The method described here for such a wave-number concentration makes use of an expansion in spherical harmonics, and requires a relatively small number of measurement points for a good approximate achievement of a plane wave. The measurement points are on a spherical surface surrounding the array of loudspeakers. The input signals for the individual loudspeakers can be derived without a matrix inversion or without explicit assumptions about the loudspeakers. The mathematical development involves spherical harmonics and three-dimensional Fourier transforms. Some numerical examples are given, with various assumptions concerning the nature of the loudspeakers, that support the premise that the method described in the present paper may be useful in applications.

  9. Application of the Pseudopotential Method to the Theory of Semiconductors.

    NASA Astrophysics Data System (ADS)

    Silver, Mark

    Available from UMI in association with The British Library. The Empirical Pseudopotential Method (EPM) has been used in this thesis to investigate four areas of interest in semiconductor research, namely, strain-induced valence subband splittings, simple analytical k.p expressions for conduction and valence band dispersions, 'universal' behaviour of conduction band non-parabolicity, and Gamma -L mixing in (111) grown superlattices. In the first of these the EPM was used to calculate directly the valence band structure of strained materials. From this the strain-induced matrix element, C_4, which is proportional both to the axial strain, varepsilon_{ax}, and the in-plane wave-vector, k_|, was deduced for all common III-V materials and selected II-VI's. The effect of C_4 on properties of quantum wells is discussed with particular emphasis on layers under biaxial tension. The EPM was then used to test analytical k.p expressions that attempt to describe the conduction band anisotropy and valence bands along the (001) direction around the zone centre Gamma point. A number of expressions have been derived which span a wide range of band gap and spin-orbit splitting energies. The EPM has allowed the range of applicability of these expressions to be determined. The conduction band dispersion around the Gamma point generated by the EPM was also used to verify the 'universal' behaviour of common semiconductor materials when energy and wavevector are scaled in an appropriate manner. Surprisingly we find the universality of this type is still present even when non-parabolicity effects are expected to be important. This analysis was initially done on the direct gap III-V semiconductors but was then extended to the indirect gap III-V and group IV materials, as well as the direct gap II-VI's. A modified 2-band k.p model was devised which reproduced the universal behaviour and allowed interpretation of the results using Harrison's model-solid theory. Finally superlattice (SL

  10. Pseudopotentials for an ultracold dipolar gas

    NASA Astrophysics Data System (ADS)

    Whitehead, T. M.; Conduit, G. J.

    2016-02-01

    A gas of ultracold molecules interacting via the long-range dipolar potential offers a highly controlled environment in which to study strongly correlated phases. However, at particle coalescence the divergent 1 /r3 dipolar potential and associated pathological wave function hinder computational analysis. For a dipolar gas constrained to two dimensions we overcome these numerical difficulties by proposing a pseudopotential that is explicitly smooth at particle coalescence, resulting in a 2000-times speedup in diffusion Monte Carlo calculations. The pseudopotential delivers the scattering phase shifts of the dipolar interaction with an accuracy of 10-5 and predicts the energy of a dipolar gas to an accuracy of 10-4EF in a diffusion Monte Carlo calculation.

  11. Propagation of plane waves in a rotating transversely isotropic two temperature generalized thermoelastic solid half-space with voids

    NASA Astrophysics Data System (ADS)

    Bijarnia, R.; Singh, B.

    2016-05-01

    The paper is concerned with the propagation of plane waves in a transversely isotropic two temperature generalized thermoelastic solid half-space with voids and rotation. The governing equations are modified in the context of Lord and Shulman theory of generalized thermoelasticity and solved to show the existence of four plane waves in the x - z plane. Reflection of these plane waves from thermally insulated stress free surface is also studied to obtain a system of four non-homogeneous equations. For numerical computations of speed and reflection coefficients, a particular material is modelled as transversely isotropic generalized thermoelastic solid half-space. The speeds of plane waves are computed against the angle of propagation to observe the effects of two temperature and rotation. Reflection coefficients of various reflected waves are also computed against the angle of incidence to observe the effects of various parameters.

  12. Love wave tomography in southern Africa from a two-plane-wave inversion method

    NASA Astrophysics Data System (ADS)

    Li, Aibing; Li, Lun

    2015-08-01

    Array measurements of surface wave phase velocity can be biased by multipath arrivals. A two-plane-wave (TPW) inversion method, in which the incoming wavefield is represented by the interference of two plane waves, is able to account for the multipath effect and solve for laterally varying phase velocity. Despite broad applications of the TPW method, its usage has been limited to Rayleigh waves. In this study, we have modified the TPW approach and applied it to Love waves. Main modifications include decomposing Love wave amplitude on the transverse component to x and y components in a local Cartesian system for each earthquake and using both components in the inversion. Such decomposition is also applied to the two plane waves to predict the incoming wavefield of an earthquake. We utilize fundamental mode Love wave data recorded at 85 broad-band stations from 69 distant earthquakes and solved for phase velocity in nine frequency bands with centre periods ranging from 34 to 100 s. The average phase velocity in southern Africa increases from 4.30 km s-1 at 34 s to 4.87 km s-1 at 100 s. Compared with predicted Love wave phase velocities from the published 1-D SV velocity model and radial anisotropy model in the region, these values are compatible from 34 to 50 s and slightly higher beyond 50 s, indicating radial anisotropy of VSH > VSV in the shallow upper mantle. A high Love wave velocity anomaly is imaged in the central and southern Kaapvaal craton at all periods, reflecting a cold and depleted cratonic lithosphere. A low velocity anomaly appears in the Bushveld Complex from 34 to 50 s, which can be interpreted as being caused by high iron content from an intracratonic magma intrusion. The modified TPW method provides a new way to measure Love wave phase velocities in a regional array, which are essential in developing radial anisotropic models and understanding the Earth structure in the crust and upper mantle.

  13. Relativistic Two-Boson System in Presence of Electromagnetic Plane Wave

    NASA Astrophysics Data System (ADS)

    Droz-Vincent, Ph.

    2016-09-01

    The relativistic two-body problem is considered for spinless particles subject to an external electromagnetic field. When this field is made of the monochromatic superposition of two counter-propagating plane waves (and provided the mutual interaction between particles is known), it is possible to write down explicitly a pair of coupled wave equations (corresponding to a pair of mass-shell constraints) which takes into account also the field contribution. These equations are manifestly covariant; constants of the motion are exhibited, so one ends up with a reduced problem involving five degrees of freedom.

  14. Limits of the plane wave approximation in the measurement of molecular properties.

    PubMed

    Walters, Zachary B; Tonzani, Stefano; Greene, Chris H

    2008-10-01

    Rescattering electrons offer great potential as probes of molecular properties on ultrafast timescales. The most famous example is molecular tomography, in which high harmonic spectra of oriented molecules are mapped to "tomographic images" of the relevant molecular orbitals. The accuracy of such reconstructions can be greatly affected by the distortion of scattering wave functions from their asymptotic forms due to interactions with the parent ion. We investigate the validity of the commonly used plane wave approximation in molecular tomography, showing how such distortions affect the resulting orbital reconstructions.

  15. Plane-wave ultrasound beamforming using a nonuniform fast Fourier transform.

    PubMed

    Kruizinga, Pieter; Mastik, Frits; de Jong, Nico; van der Steen, Antonius F W; van Soest, Gijs

    2012-12-01

    Beamforming of plane-wave ultrasound echo signals in the Fourier domain provides fast and accurate image reconstruction. Conventional implementations perform a k-space interpolation from the uniform sampled grid to a nonuniform acoustic dispersion grid. In this paper, we demonstrate that this step can be replaced by a nonuniform Fourier transform. We study the performance of the nonuniform fast Fourier transform (NUFFT) in terms of signal-to-noise ratio and computational cost, and show that the NUFFT offers an advantage in the trade-off between speed and accuracy, compared with other frequency-domain beamforming strategies.

  16. Exact soliton-on-plane-wave solutions for two-component Bose-Einstein condensates.

    PubMed

    Li, Lu; Malomed, Boris A; Mihalache, Dumitru; Liu, W M

    2006-06-01

    By means of the Darboux transformation, we obtain analytical solutions for a soliton set on top of a plane-wave background in coupled Gross-Pitaevskii equations describing a binary Bose-Einstein condensate. We consider basic properties of the solutions with and without the cross interaction [cross phase modulation (XPM)] between the two components of the background. In the absence of the XPM, this solutions maintain properties of one-component condensates, such as the modulation instability (MI); in the presence of the cross interaction, the solutions exhibit different properties, such as restriction of the MI and soliton splitting.

  17. Plane-Wave Compounding in Automated Breast Volume Scanning: A Phantom-Based Study.

    PubMed

    Holländer, Branislav; Hendriks, Gijs A G M; Mann, Ritse M; Hansen, Hendrik H G; de Korte, Chris L

    2016-10-01

    The goal of this study was to assess whether it is viable to implement plane-wave imaging in the Automated Breast Volume Scanner (ABVS) to speed up the acquisition process. This would allow breath-hold examinations, thus reducing breathing artifacts without loss of imaging quality. A calibration phantom was scanned in an Automated Breast Volume Scanner-mimicking setup using both dynamic receive focusing with a fixed transmit focus and unfocused plane-wave compounding. Contrast-to-noise ratio and lateral resolution were compared using two beamforming schemes, delay-and-sum and Stolt's f-k algorithm. Plane-wave compounding using only 11 compounding angles and Stolt's f-k algorithm provided image quality similar to that of focused transmission with dynamic receive focusing (contrast-to-noise ratios = 10.3 and 10.8 dB for Stolt's f-k migration with Hann apodization and focused transmission, respectively; full width at half-maximum = 0.38 and 0.4 mm, respectively; all at 30-mm depth with transmit focus at 30 mm) with a higher signal-to-noise ratio at all depths. Furthermore, a full 3-D volume of a breast-mimicking phantom was scanned using this optimal set of compounding angles and different speeds (10, 20 and 50 mm/s) to assess the impact of scanning time on image quality. Only minor differences in contrast-to-noise ratio were found (cyst 1: 6.0 ± 0.3 dB, cyst 2: 5.5 ± 0.2 dB, cyst 3: 5.7 ± 0.5 dB). These differences could not be correlated to the movement speeds, indicating that acquisition speed does not significantly affect image quality. Our results suggest that plane-wave imaging will enable breath-hold automated breast volume scanning examinations, eliminating breathing artifacts while otherwise preserving similar image quality.

  18. Light propagation analysis using a translated plane angular spectrum method with the oblique plane wave incidence.

    PubMed

    Son, Hyeon-ho; Oh, Kyunghwan

    2015-05-01

    A novel angular spectrum method was proposed to numerically analyze off-axis free-space light propagation on a translated plane to an arbitrary angle. Utilizing a shifted angular spectrum method based on an oblique incident plane wave assumption, a generalized light propagation formulation was obtained in a wide range of both tilt angles and sampling intervals, which overcame the limitations of prior attempts. A detailed comparison of the proposed angular spectrum method with prior methods is numerically presented for diffractive optics and computer-generated holograms. The validity of the proposed method was confirmed experimentally by reconstructing a digital holographic image using a spatial light modulator.

  19. Plane Wave in the System of N Particles with Zero Angular Momentum

    NASA Astrophysics Data System (ADS)

    Meremianin, A. V.

    2016-09-01

    The wave function of the system of N ≥ 3 free particles having zero total angular momentum is considered. This function is defined as the zeroth order multipole coefficient in the expansion of the product of N plane waves over the set of finite rotation matrices (i.e. Wigner D-functions). Several integral representations for that wave-function are obtained. It is demonstrated that the structure of the wave function for arbitrary number of particles remains that of the four-particle case. Special attention is paid to the "in-plane" geometry when particle's momenta vectors (or their conjugated Jacobi vectors) are coplanar.

  20. A full 3D plane-wave-expansion model for 1-3 piezoelectric composite structures.

    PubMed

    Wilm, Mikaël; Ballandras, Sylvain; Laude, Vincent; Pastureaud, Thomas

    2002-09-01

    The plane-wave-expansion (PWE) approach dedicated to the simulation of periodic devices has been extended to 1-3 connectivity piezoelectric composite structures. The case of simple but actual piezoelectric composite structures is addressed, taking piezoelectricity, acoustic losses, and electrical excitation conditions rigorously into account. The material distribution is represented by using a bidimensional Fourier series and the electromechanical response is simulated using a Bloch-Floquet expansion together with the Fahmy-Adler formulation of the Christoffel problem. Application of the model to 1-3 connectivity piezoelectric composites is reported and compared to previously published analyses of this problem.

  1. Extracting chemical information from plane wave calculations by a 3D 'fuzzy atoms' analysis

    NASA Astrophysics Data System (ADS)

    Bakó, I.; Stirling, A.; Seitsonen, A. P.; Mayer, I.

    2013-03-01

    Bond order and valence indices have been calculated by the method of the three-dimensional 'fuzzy atoms' analysis, using the numerical molecular orbitals obtained from plane wave DFT calculations, i.e., without introducing any external atom-centered functions. Weight functions of both Hirshfeld and Becke types have been applied. The results are rather close to the similar 'fuzzy atoms' ones obtained by using atom-centered basis sets and agree well with the chemical expectations, stressing the power of the genuine chemical concepts.

  2. A precise angular spectrum of plane-waves diffraction theory for leaky wave materials

    NASA Astrophysics Data System (ADS)

    Hunt, W. D.; Hunsinger, B. J.

    1988-08-01

    This paper describes a computational leaky-wave diffraction-theory technique which very accurately describes leaky wave propagation; it combines the method of Kharusi and Farnell (1971) based on the angular spectrum of plane-wave formalism with the measured values of velocity and attenuation provided by the slowness surface measurement method of Murray and Ash (1977). The technique was shown to predict accurately the magnitude and phase of beam profiles propagating over long distances in bare-surface 100-plane-cut semiinsulating GaAs. The technique was also shown to be a good predictor of beam profile propagation through metallic grating structures required in acoustic charge transport device application.

  3. Debye series of normally incident plane-wave scattering by an infinite multilayered cylinder.

    PubMed

    Li, Renxian; Han, Xiang'e; Jiang, Huifen; Ren, Kuan Fang

    2006-08-20

    We derive the formula of the Debye-series decomposition for normally incident plane-wave scattering by an infinite multilayered cylinder. A comparison of the scattering diagrams calculated by the Debye series and Mie theory for a graded-index polymer optical fiber is given and the agreement is found to be satisfied. This approach permits us to simulate the rainbow intensity distribution of any single order and the interference of several orders, which is of good use to the study of the scattering characteristics of an inhomogeneous cylinder and to the measurement of the refractive index profile of an inhomogeneous cylinder. PMID:16892131

  4. Radiation reaction from QED: Lightfront perturbation theory in a plane wave background

    NASA Astrophysics Data System (ADS)

    Ilderton, Anton; Torgrimsson, Greger

    2013-07-01

    We derive dynamical, real time radiation reaction effects from lightfront QED. Combining the Hamiltonian formalism with a plane wave background field, the calculation is performed in the Furry picture for which the background is treated exactly while interactions between quantum fields are treated in perturbation theory as normal. We work to a fixed order in perturbation theory, but no other approximation is made. The literature contains many proposals for the correct classical equation describing a radiating particle; we take the classical limit of our results and identify which equations are consistent with QED.

  5. The transmission of acoustic energy by a finite cylindrical shell excited by external plane waves

    NASA Astrophysics Data System (ADS)

    Cacciolati, C.; Gotteland, M.; Barbe, M.

    A qualitative method is presented for sensitivity analyses of acoustic coupling between cylindrical shells such as found in aerospace structures. The shells are excited by an exterior plane wave. The analysis is carried out in terms of coupling among the exterior and structural natural modes and the structural and cavity natural modes. Strong coupling is shown to be limited to cases of coincidence of resonance frequencies and when numerous identical incident waves arrive from multiple directions. Coupling will in any case be confined to low frequencies. Limits are defined for the necessary number of frequencies which must be considered when predicting whether or not coupling will occur.

  6. Fast solution of elliptic partial differential equations using linear combinations of plane waves.

    PubMed

    Pérez-Jordá, José M

    2016-02-01

    Given an arbitrary elliptic partial differential equation (PDE), a procedure for obtaining its solution is proposed based on the method of Ritz: the solution is written as a linear combination of plane waves and the coefficients are obtained by variational minimization. The PDE to be solved is cast as a system of linear equations Ax=b, where the matrix A is not sparse, which prevents the straightforward application of standard iterative methods in order to solve it. This sparseness problem can be circumvented by means of a recursive bisection approach based on the fast Fourier transform, which makes it possible to implement fast versions of some stationary iterative methods (such as Gauss-Seidel) consuming O(NlogN) memory and executing an iteration in O(Nlog(2)N) time, N being the number of plane waves used. In a similar way, fast versions of Krylov subspace methods and multigrid methods can also be implemented. These procedures are tested on Poisson's equation expressed in adaptive coordinates. It is found that the best results are obtained with the GMRES method using a multigrid preconditioner with Gauss-Seidel relaxation steps. PMID:26986436

  7. 2, Pulse-mode expansions and refractive indices in plane-wave propagation

    SciTech Connect

    Shore, B.W.; Sacks, R.; Karr, T.; Morris, J.; Paisner, J.A.

    1987-06-20

    This memo presents basic background theory for treating simultaneous propagation of electromagnetic pulses of various colors, directed along a common ray, through a molecular vapor. The memo discusses some techniques for expanding the positive frequency part of the transverse electric field into pulse modes, characterized by carrier frequencies within a modulated envelope. We discuss, in the approximation of plane waves with slowly varying envelopes, a set of uncoupled envelope equations in which a polarization mode-envelope acts as a source for an electric-field envelope. These equations, when taken with a prescription for the polarization field, are the basic equations of plane-wave pulse propagation through a molecular medium. We discuss two ways of treating dispersive media, one based upon expansions in the frequency domain and the other based in the time domain. In both cases we find envelope equations that involve group velocities. This memo represents a portion of a more extensive treatment of propagation to be presented separately. Many of the equations presented here have been described in various books and articles. They are collected and described here as a summary and review of contemporary theory.

  8. Whole body exposure at 2100 MHz induced by plane wave of random incidences in a population

    NASA Astrophysics Data System (ADS)

    Conil, Emmanuelle; Hadjem, Abdelhamid; El Habachi, Aimad; Wiart, J.

    2010-11-01

    In this article, the whole body exposure induced by plane wave coming from a random direction of arrival is analyzed at 2100 MHz. This work completes previous studies on the influence of different parameters on the whole body exposure (such as morphology, frequency or usage in near field). The Visible Human phantom has been used to build a surrogate model to predict the whole body exposure depending on the highlighted surface of the phantom and on the direction of arrival of the incident plane wave. For the Visible Human, the error on the whole body averaged Specific Absorption Rate (SAR) is on average 4%. The surrogate model is applied to other 3D anthropomorphic phantoms for a frontal incidence with an averaged error of 10%. The great interest of the surrogate model is the possibility to apply a Monte Carlo process to assess probability distribution function of a population. A recent French anthropometric database of more than 3500 adults is used to build the probability distribution function of the whole body SAR for a random direction of arrival.

  9. Plane-wave superpositions defined by orthonormal scalar functions on two- and three-dimensional manifolds

    PubMed

    Borzdov

    2000-04-01

    Vector plane-wave superpositions defined by a given set of orthonormal scalar functions on a two- or three-dimensional manifold-beam manifold-are treated. We present a technique for composing orthonormal beams and some other specific types of fields such as three-dimensional standing waves, moving and evolving whirls. It can be used for any linear fields, in particular, electromagnetic fields in complex media and elastic fields in crystals. For electromagnetic waves in an isotropic medium or free space, unique families of exact solutions of Maxwell's equations are obtained. The solutions are illustrated by calculating fields, energy densities, and energy fluxes of beams defined by the spherical harmonics. It is shown that the obtained results can be used for a transition from the plane-wave approximation to more accurate models of real incident beams in free-space techniques for characterizing complex media. A mathematical formalism convenient for the treatment of various beams defined by the spherical harmonics is presented.

  10. Scaled plane-wave Born cross sections for atoms and molecules

    NASA Astrophysics Data System (ADS)

    Tanaka, H.; Brunger, M. J.; Campbell, L.; Kato, H.; Hoshino, M.; Rau, A. R. P.

    2016-04-01

    Integral cross sections for optically allowed electronic-state excitations of atoms and molecules by electron impact, by applying scaled plane-wave Born models, are reviewed. Over 40 years ago, Inokuti presented an influential review of charged-particle scattering, based on the theory pioneered by Bethe forty years earlier, which emphasized the importance of reliable cross-section data from low eV energies to high keV energies that are needed in many areas of radiation science with applications to astronomy, plasmas, and medicine. Yet, with a couple of possible exceptions, most computational methods in electron-atom scattering do not, in general, overlap each other's validity range in the region from threshold up to 300 eV and, in particular, in the intermediate region from 30 to 300 eV. This is even more so for electron-molecule scattering. In fact this entire energy range is of great importance and, to bridge the gap between the two regions of low and high energy, scaled plane-wave Born models were developed to provide reliable, comprehensive, and absolute integral cross sections, first for ionization by Kim and Rudd and then extended to optically allowed electronic-state excitation by Kim. These and other scaling models in a broad, general application to electron scattering from atoms and molecules, their theoretical basis, and their results for cross sections along with comparison to experimental measurements are reviewed. Where possible, these data are also compared to results from other computational approaches.

  11. Quantum Larmor Radiation from a Moving Charge in AN Electromagnetic Plane Wave Background

    NASA Astrophysics Data System (ADS)

    Nakamura, Gen; Yamamoto, Kazuhiro

    2012-09-01

    We extend our previous work [Phys. Rev. D83, 045030 (2011)], which investigated the first-order quantum effect in the Larmor radiation from a moving charge in a spatially homogeneous time-dependent electric field. Specifically, we investigate the quantum Larmor radiation from a moving charge in a monochromatic electromagnetic plane wave background based on the scalar quantum electrodynamics at the lowest order of the perturbation theory. Using the in-in formalism, we derive the theoretical formula of the total radiation energy from a charged particle in the initial states being at rest and being in a relativistic motion. Expanding the theoretical formula in terms of the Planck constant ℏ, we obtain the first-order quantum effect on the Larmor radiation. The quantum effect generally suppresses the total radiation energy compared with the prediction of the classical Larmor formula, which is a contrast to the previous work. The reason is explained by the fact that the radiation from a moving charge in a monochromatic electromagnetic plane wave is expressed in terms of the inelastic collisions between an electron and photons of the background electromagnetic waves.

  12. Ioffe-Regel crossover for plane-wave vibrational excitations in vitreous silica

    NASA Astrophysics Data System (ADS)

    Taraskin, S. N.; Elliott, S. R.

    2000-05-01

    The first Ioffe-Regel crossover for vibrational plane waves (when wavelength and mean free path are comparable) has been investigated theoretically for models of vitreous silica (v-SiO2) constructed by molecular dynamics. The crossover is found to be from a state of weak scattering to one of strong scattering, not vibrational localization. Three methods have been used to investigate the crossover: an analysis of the time evolution of a vibrational plane wave, a spectral-density analysis in frequency space, and an analysis of the final scattered state in momentum space. The first Ioffe-Regel crossover frequency is found by all three methods to be ~1 THz for v-SiO2, for both longitudinal and transverse polarizations. A second Ioffe-Regel crossover occurs at ~6 THz for v-SiO2, corresponding to the frequency at which the mean free path is minimal (comparable to the interatomic spacing), and the spectral-density width is maximal (comparable to the frequency range of the vibrational density of states).

  13. Fast inhomogeneous plane wave algorithm for the analysis of electromagnetic scattering

    NASA Astrophysics Data System (ADS)

    Hu, Bin; Chew, Weng Cho; Velamparambil, Sanjay

    2001-01-01

    The fast inhomogeneous plane wave algorithm has been developed to accelerate the solution of three-dimensional electromagnetic scattering problems in free space. By expanding the kernel of the Green's function using the Weyl identity and choosing a proper steepest descent path, the diagonalization of the translation matrix is achieved after the interpolation and extrapolation techniques are applied. The proposed algorithm is implemented on top of the scalable multipole engine, a portable implementation of the dynamic multilevel fast multipole algorithm for distributed-memory computers. The computational time per matrix vector multiplication is reduced to O(NlogN) and the memory requirement is reduced to O(N), where N is the number of unknowns in the discretized integral equation. The algorithm is validated by applying it to the solution of the electromagnetic scattering from the perfect electric conducting scatterers. This approach can be easily extended to more general problems with complicated Green's function expressed in terms of the plane wave spectral integrals, such as the ones encountered in the multilayered medium studies.

  14. Radiation of de-excited electrons at large times in a strong electromagnetic plane wave

    NASA Astrophysics Data System (ADS)

    Kazinski, P. O.

    2013-12-01

    The late time asymptotics of the physical solutions to the Lorentz-Dirac equation in the electromagnetic external fields of simple configurations-the constant homogeneous field, the linearly polarized plane wave (in particular, the constant uniform crossed field), and the circularly polarized plane wave-are found. The solutions to the Landau-Lifshitz equation for the external electromagnetic fields admitting a two-parametric symmetry group, which include as a particular case the above mentioned field configurations, are obtained. Some general properties of the total radiation power of a charged particle are established. In particular, for a circularly polarized wave and constant uniform crossed fields, the total radiation power in the asymptotic regime is independent of the charge and the external field strength, when expressed in terms of the proper-time, and equals a half the rest energy of a charged particle divided by its proper-time. The spectral densities of the radiation power formed on the late time asymptotics are derived for a charged particle moving in the external electromagnetic fields of the simple configurations pointed above. This provides a simple method to verify experimentally that the charged particle has reached the asymptotic regime.

  15. Combined perfusion and doppler imaging using plane-wave nonlinear detection and microbubble contrast agents.

    PubMed

    Tremblay-Darveau, Charles; Williams, Ross; Milot, Laurent; Bruce, Matthew; Burns, Peter N

    2014-12-01

    Plane-wave imaging offers image acquisition rates at the pulse repetition frequency, effectively increasing the imaging frame rates by up to two orders of magnitude over conventional line-by-line imaging. This form of acquisition can be used to achieve very long ensemble lengths in nonlinear modes such as pulse inversion Doppler, which enables new imaging trade-offs that were previously unattainable. We first demonstrate in this paper that the coherence of microbubble signals under repeated exposure to acoustic pulses of low mechanical index can be as high as 204 ± 5 pulses, which is long enough to allow an accurate power Doppler measurement. We then show that external factors, such as tissue acceleration, restrict the detection of perfusion at the capillary level with linear Doppler, even if long Doppler ensembles are considered. Hence, perfusion at the capillary level can only be detected with ultrasound through combined microbubbles and Doppler imaging. Finally, plane-wave contrast-enhanced power and color Doppler are performed on a rabbit kidney in vivo as a proof of principle. We establish that long pulse-inversion Doppler sequences and conventional wall-filters can create an image that simultaneously resolves both the vascular morphology of veins and arteries, and perfusion at the capillary level with frame rates above 100 Hz.

  16. Fast solution of elliptic partial differential equations using linear combinations of plane waves

    NASA Astrophysics Data System (ADS)

    Pérez-Jordá, José M.

    2016-02-01

    Given an arbitrary elliptic partial differential equation (PDE), a procedure for obtaining its solution is proposed based on the method of Ritz: the solution is written as a linear combination of plane waves and the coefficients are obtained by variational minimization. The PDE to be solved is cast as a system of linear equations A x =b , where the matrix A is not sparse, which prevents the straightforward application of standard iterative methods in order to solve it. This sparseness problem can be circumvented by means of a recursive bisection approach based on the fast Fourier transform, which makes it possible to implement fast versions of some stationary iterative methods (such as Gauss-Seidel) consuming O (N logN ) memory and executing an iteration in O (N log2N ) time, N being the number of plane waves used. In a similar way, fast versions of Krylov subspace methods and multigrid methods can also be implemented. These procedures are tested on Poisson's equation expressed in adaptive coordinates. It is found that the best results are obtained with the GMRES method using a multigrid preconditioner with Gauss-Seidel relaxation steps.

  17. Stolt’s f-k migration for plane wave ultrasound imaging

    PubMed Central

    Garcia, Damien; Le Tarnec, Louis; Muth, Stéphan; Montagnon, Emmanuel; Porée, Jonathan; Cloutier, Guy

    2013-01-01

    Ultrafast ultrasound is an emerging modality that offers new perspectives and opportunities in medical imaging. Plane wave imaging (PWI) allows one to attain very high frame rates by transmission of planar ultrasound wavefronts. As a plane wave reaches a given scatterer, the latter becomes a secondary source emitting upward spherical waves and creating a diffraction hyperbola in the received RF (radio-frequency) signals. To produce an image of the scatterers, all the hyperbolas must be migrated back to their apexes. In order to perform beamforming of plane wave echo RFs and return high-quality images at high frame rates, we propose a new migration method carried out in the frequency-wavenumber (f-k) domain. The f-k migration for PWI has been adapted from the Stolt migration for seismic imaging. This migration technique is based on the exploding reflector model (ERM), which consists in assuming that all the scatterers explode in concert and become acoustic sources. The classical ERM model, however, is not appropriate for PWI. We showed that the ERM can be made suitable for PWI by a spatial transformation of the hyperbolic traces present in the RF data. In vitro experiments were performed to sketch the advantages of PWI with Stolt’s f-k migration over the conventional delay-and-sum (DAS) approach. The Stolt’s f-k migration was also compared with the Fourier-based method developed by J-Y Lu. Our findings show that multi-angle compounded f-k migrated images are of quality similar to those obtained with a state-of-the-art dynamic focusing mode. This remained true even with a very small number of steering angles thus ensuring a highly competitive frame rate. In addition, the new FFT-based f-k migration provides comparable or better contrast-to-noise ratio and lateral resolution than the Lu’s and DAS migration schemes. Matlab codes of the Stolt’s f-k migration for PWI are provided. PMID:24626107

  18. Systematic pseudopotentials from reference eigenvalue sets for DFT calculations: Pseudopotential files

    PubMed Central

    Rivero, Pablo; Manuel García-Suárez, Víctor; Pereñiguez, David; Utt, Kainen; Yang, Yurong; Bellaiche, Laurent; Park, Kyungwha; Ferrer, Jaime; Barraza-Lopez, Salvador

    2015-01-01

    We present in this article a pseudopotential (PP) database for DFT calculations in the context of the SIESTA code [1–3]. Comprehensive optimized PPs in two formats (psf files and input files for ATM program) are provided for 20 chemical elements for LDA and GGA exchange-correlation potentials. Our data represents a validated database of PPs for SIESTA DFT calculations. Extensive transferability tests guarantee the usefulness of these PPs. PMID:26217711

  19. Mixing of collinear plane wave pulses in elastic solids with quadratic nonlinearity.

    PubMed

    Chen, Zimu; Tang, Guangxin; Zhao, Youxun; Jacobs, Laurence J; Qu, Jianmin

    2014-11-01

    This paper derives a set of necessary and sufficient conditions for generating resonant waves by two propagating time-harmonic plane waves. It is shown that in collinear mixing, a resonant wave can be generated either by a pair of longitudinal waves, in which case the resonant mixing wave is also a longitudinal wave, or by a pair of longitudinal and transverse waves, in which case the resonant wave is a transverse wave. In addition, the paper obtains closed-form analytical solutions to the resonant waves generated by two collinearly propagating sinusoidal pulses. The results show that amplitude of the resonant pulse is proportional to the mixing zone size, which is determined by the spatial lengths of the input pulses. Finally, numerical simulations based on the finite element method and experimental measurements using one-way mixing are conducted. It is shown that both numerical and experimental results agree well with the analytical solutions. PMID:25373942

  20. Cavity-based linear polarizer immune to the polarization direction of an incident plane wave.

    PubMed

    Wang, Jiang; Shen, Zhongxiang; Gao, Xiang; Wu, Wen

    2016-01-15

    We herein report a linear polarizer based on a 2D array of substrate integrated waveguide cavities, which can convert an arbitrary linearly polarized (LP) incident wave into an outgoing LP wave in a specified polarization direction with constant transmittance. Two orthogonal slots etched on the front surface of the cavity are utilized to couple a wave of arbitrary polarization into the cavity, while another slot on the back side helps to couple the field out along a desired polarization direction. Microwave experiments are performed as a proof of concept. The proposed polarizer exhibits very good performance with stable transmittance as 50% and a polarization extinction ratio over 45 dB. The new polarizer is potentially useful in novel polarization-selective devices that are immune to the polarization direction of an incident plane wave.

  1. Microwave radiation force and torque on a disk resonator excited by a circularly polarized plane wave

    NASA Astrophysics Data System (ADS)

    Makarov, S.; Kulkarni, S.

    2004-05-01

    A numerical simulation method [S. Makarov and S. Kulkarni, Appl. Phys. Lett. 84, 1600 (2004)] is used in order to determine the radiation force and radiation torque on a parallel-plate disk resonator, whose size is comparable to wavelength. The method is based on the MOM solution of the electric-field integral equation, accurate calculation of the near field, and removal of the self-interaction terms responsible for the pinch effect. The local force/torque distribution at the normal incidence of a circularly polarized plane wave is found. It is observed that, at the resonance, the individual disks are subject to unexpectedly large local force densities, despite the fact that the net radiation force on the resonator remains very small. On the other hand, the total axial torque on the disk resonator also increases at the resonance.

  2. Exact solution to plane-wave scattering by an ideal "left-handed" wedge.

    PubMed

    Monzon, Cesar; Forester, Donald W; Smith, Douglas; Loschialpo, Peter

    2006-02-01

    An exact analytical solution to the problem of plane-wave diffraction by a penetrable left-handed medium (LHM) epsilon = micro = -1 wedge of arbitrary angle (subject to valid physical constraints) is presented. Standard analysis involving discontinuous angular eigenfunctions and even/odd symmetry decomposition resulted in a discrete spectrum leading to a series solution resembling the traditional perfect electric conductor wedge solution but exhibiting the expected negative refraction phenomenology. Numerical results are presented, some of which seemed paradoxical but are explainable by classical means. A new type of illusory edge radiation is observed and explained. Also, a novel edge-launched interface standing wave is observed on the directly illuminated side. The exact analytical solution is verified by comparison with finite-difference time-domain simulation on causal LHM materials.

  3. Scattering from cylinders using the two-dimensional vector plane wave spectrum.

    PubMed

    Pawliuk, Peter; Yedlin, Matthew

    2011-06-01

    The two-dimensional vector plane wave spectrum (VPWS) is scattered from parallel circular cylinders using a boundary value solution with the T-matrix formalism. The VPWS allows us to define the incident, two-dimensional electromagnetic field with an arbitrary distribution and polarization, including both radiative and evanescent components. Using the fast Fourier transform, we can quickly compute the multiple scattering of fields that have any particular functional or numerical form. We perform numerical simulations to investigate a grating of cylinders that is capable of converting an evanescent field into a set of propagating beams. The direction of propagation of each beam is directly related to a spatial frequency component of the incident evanescent field.

  4. Scattering of pulsed plane wave from a symmetrical groove doublet configuration.

    PubMed

    Ding, Lan; Liu, Jinsong; Wang, Dong; Wang, Kejia

    2010-12-20

    We have provided theoretical study on the spectral and temporal properties of the scattering of pulsed plane wave from a symmetrical groove doublet configuration. Based on the numerical calculation results, we show that the spectrum and the waveform of the scattered field are sensitive to the shape of the rectangular grooves when the grooves are deep enough. In both spectral and temporal domain, a damped oscillatory behavior occurs when the groove spacing increases. Furthermore, the spectral and temporal dependences of the angular distribution are consisted of interference-like fringe patterns. These patterns are sensitive to the size of the groove width and spacing rather than the groove shape when the depth is small enough. Our study takes the analysis of pulse scattering by finite grooves a step further on the theoretical side, and offers opportunities for the control of spectral and temporal properties of pulsed scattered wave in low frequency regime such as THz and microwave domain.

  5. Pulsed plane wave analytic solutions for generic shapes and the validation of Maxwell's equations solvers

    NASA Technical Reports Server (NTRS)

    Yarrow, Maurice; Vastano, John A.; Lomax, Harvard

    1992-01-01

    Generic shapes are subjected to pulsed plane waves of arbitrary shape. The resulting scattered electromagnetic fields are determined analytically. These fields are then computed efficiently at field locations for which numerically determined EM fields are required. Of particular interest are the pulsed waveform shapes typically utilized by radar systems. The results can be used to validate the accuracy of finite difference time domain Maxwell's equations solvers. A two-dimensional solver which is second- and fourth-order accurate in space and fourth-order accurate in time is examined. Dielectric media properties are modeled by a ramping technique which simplifies the associated gridding of body shapes. The attributes of the ramping technique are evaluated by comparison with the analytic solutions.

  6. Integrable open spin chain in super Yang-Mills and the plane-wave/SYM duality

    NASA Astrophysics Data System (ADS)

    Chen, Bin; Wang, Xiao-Jun; Wu, Yong-Shi

    2004-02-01

    We investigate the integrable structures in an Script N = 2 superconformal Sp(N) Yang-Mills theory with matter, which is dual to an open+closed string system. We restrict ourselves to the BMN operators that correspond to free string states. In the closed string sector, an integrable structure is inherited from its parent theory, Script N = 4 SYM. For the open string sector, the planar one-loop mixing matrix for gauge invariant holomorphic scalar operators is identified with the hamiltonian of an integrable SU(3) open spin chain. Using the K-matrix formalism we identify the integrable open-chain boundary conditions that correspond to string boundary conditions. The solutions to the algebraic Bethe ansatz equations (ABAE) with a few impurities are shown to recover the anomalous dimensions that exactly match the spectrum of free open string in the plane-wave background. We also discuss the properties of the solutions of ABAE beyond the BMN regime.

  7. Harmonic analysis of lossy, piezoelectric composite transducers using the plane wave expansion method.

    PubMed

    Orr, Leigh-Ann; Mulholland, Anthony J; O'Leary, Richard L; Hayward, Gordon

    2008-12-01

    Periodic composite ultrasonic transducers offer many advantages but the periodic pillar architecture can give rise to unwanted modes of vibration which interfere with the piston like motion of the fundamental thickness mode. In this paper, viscoelastic loss is incorporated into a three-dimensional plane wave expansion model (PWE) of these transducers. A comparison with experimental and finite element data is conducted and a design to damp out these lateral modes is investigated. Scaling and regularisation techniques are introduced to the PWE method to reduce ill-conditioning in the large matrices which can arise. The identification of the modes of vibration is aided by examining profiles of the displacements, electrical potential and Poynting vector. The dispersive behaviour of a 2-2 composite transducer with high shear attenuation in the passive phase is examined. The model shows that the use of a high shear attenuation filler material improves the frequency band gap surrounding the fundamental thickness mode.

  8. In-plane vibrations of a rectangular plate: Plane wave expansion modelling and experiment

    NASA Astrophysics Data System (ADS)

    Arreola-Lucas, A.; Franco-Villafañe, J. A.; Báez, G.; Méndez-Sánchez, R. A.

    2015-04-01

    Theoretical and experimental results for in-plane vibrations of a uniform rectangular plate with free boundary conditions are obtained. The experimental setup uses electromagnetic-acoustic transducers and a vector network analyzer. The theoretical calculations were obtained using the plane wave expansion method applied to the in-plane thin plate vibration theory. The agreement between theory and experiment is excellent for the lower 95 modes covering a very wide frequency range from DC to 20 kHz. Some measured normal-mode wave amplitudes were compared with the theoretical predictions; very good agreement was observed. The excellent agreement of the classical theory of in-plane vibrations confirms its reliability up to very high frequencies

  9. Kinetic theory of electromagnetic plane wave obliquely incident on bounded plasma slab

    NASA Astrophysics Data System (ADS)

    Angus, J. R.; Krasheninnikov, S. I.; Smolyakov, A. I.

    2010-10-01

    The effects of electromagnetic plane waves obliquely incident on a warm bounded plasma slab of finite length L are studied by solving the coupled Vlasov-Maxwell set of equations. It is shown that the solution can be greatly simplified in the limit where thermal effects are most important by expanding in small parameters and introducing self-similar variables. These solutions reveal that the coupling of thermal effects with the angle of incidence is negligible in the region of bounce resonance and anomalous skin effect. In the region of the anomalous skin effect, the heating is shown to scale linearly with the anomalous skin depth δa when δa≪L, in agreement with previous authors. Furthermore, for δa≫L, the heating is shown to decay with 1/δa3. The transmission is found to be exponentially larger than that predicted from a local theory in the appropriate region of the anomalous skin effect.

  10. LOBSTER: A tool to extract chemical bonding from plane-wave based DFT.

    PubMed

    Maintz, Stefan; Deringer, Volker L; Tchougréeff, Andrei L; Dronskowski, Richard

    2016-04-30

    The computer program LOBSTER (Local Orbital Basis Suite Towards Electronic-Structure Reconstruction) enables chemical-bonding analysis based on periodic plane-wave (PAW) density-functional theory (DFT) output and is applicable to a wide range of first-principles simulations in solid-state and materials chemistry. LOBSTER incorporates analytic projection routines described previously in this very journal [J. Comput. Chem. 2013, 34, 2557] and offers improved functionality. It calculates, among others, atom-projected densities of states (pDOS), projected crystal orbital Hamilton population (pCOHP) curves, and the recently introduced bond-weighted distribution function (BWDF). The software is offered free-of-charge for non-commercial research. © 2016 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.

  11. PARTICLE DISPLACEMENTS ON THE WALL OF A BOREHOLE FROM INCIDENT PLANE WAVES.

    USGS Publications Warehouse

    Lee, M.W.

    1987-01-01

    Particle displacements from incident plane waves at the wall of a fluid-filled borehole are formulated by applying the seismic reciprocity theorem to far-field displacement fields. Such displacement fields are due to point forces acting on a fluid-filled borehole under the assumption of long wavelengths. The displacement fields are analyzed to examine the effect of the borehole on seismic wave propagation, particularly for vertical seismic profiling (VSP) measurements. When the shortest wavelength of interest is approximately 25 times longer than the borehole's diameter, the scattered displacements are proportional to the first power of incident frequency and borehole diameter. When the shortest wavelength of interest is about 40 times longer than the borehole's diameter, borehole effects on VSP measurements using a wall-locking geophone are negligible.

  12. Photoacoustic clutter reduction by inversion of a linear scatter model using plane wave ultrasound measurements.

    PubMed

    Schwab, Hans-Martin; Beckmann, Martin F; Schmitz, Georg

    2016-04-01

    Photoacoustic imaging aims to visualize light absorption properties of biological tissue by receiving a sound wave that is generated inside the observed object as a result of the photoacoustic effect. In clinical applications, the strong light absorption in human skin is a major problem. When high amplitude photoacoustic waves that originate from skin absorption propagate into the tissue, they are reflected back by acoustical scatterers and the reflections contribute to the received signal. The artifacts associated with these reflected waves are referred to as clutter or skin echo and limit the applicability of photoacoustic imaging for medical applications severely. This study seeks to exploit the acoustic tissue information gained by plane wave ultrasound measurements with a linear array in order to correct for reflections in the photoacoustic image. By deriving a theory for clutter waves in k-space and a matching inversion approach, photoacoustic measurements compensated for clutter are shown to be recovered. PMID:27446669

  13. Photoacoustic clutter reduction by inversion of a linear scatter model using plane wave ultrasound measurements.

    PubMed

    Schwab, Hans-Martin; Beckmann, Martin F; Schmitz, Georg

    2016-04-01

    Photoacoustic imaging aims to visualize light absorption properties of biological tissue by receiving a sound wave that is generated inside the observed object as a result of the photoacoustic effect. In clinical applications, the strong light absorption in human skin is a major problem. When high amplitude photoacoustic waves that originate from skin absorption propagate into the tissue, they are reflected back by acoustical scatterers and the reflections contribute to the received signal. The artifacts associated with these reflected waves are referred to as clutter or skin echo and limit the applicability of photoacoustic imaging for medical applications severely. This study seeks to exploit the acoustic tissue information gained by plane wave ultrasound measurements with a linear array in order to correct for reflections in the photoacoustic image. By deriving a theory for clutter waves in k-space and a matching inversion approach, photoacoustic measurements compensated for clutter are shown to be recovered.

  14. Plane-wave Fresnel diffraction by elliptic apertures: a Fourier-based approach.

    PubMed

    Borghi, Riccardo

    2014-10-01

    A simple theoretical approach to evaluate the scalar wavefield, produced, within paraxial approximation, by the diffraction of monochromatic plane waves impinging on elliptic apertures or obstacles is presented. We find that the diffracted field can be mathematically described in terms of a Fourier series with respect to an angular variable suitably related to the elliptic parametrization of the observation plane. The convergence features of such Fourier series are analyzed, and a priori truncation criterion is also proposed. Two-dimensional maps of the optical intensity diffraction patterns are then numerically generated and compared, at a visual level, with several experimental pictures produced in the past. The last part of this work is devoted to carrying out an analytical investigation of the diffracted field along the ellipse axis. A uniform approximation is derived on applying a method originally developed by Schwarzschild, and an asymptotic estimate, valid in the limit of small eccentricities, is also obtained via the Maggi-Rubinowicz boundary wave theory.

  15. Compact range reflector analysis using the plane wave spectrum approach with an adjustable sampling rate

    NASA Astrophysics Data System (ADS)

    McKay, James P.; Rahmat-Samii, Yahya

    1991-06-01

    An improved method for determining the test zone field of compact range reflectors is presented. The plane wave spectrum (PWS) approach is used to obtain the test zone field from knowledge of the reflector aperture field distribution. The method is particularly well suited to the analysis of reflectors with a linearly serrated rim for reduced edge diffraction. Computation of the PWS of the reflector aperture field is facilitated by a closed-form expression for the Fourier transform of a polygonal window function. Inverse transformation in the test zone region is accomplished using a fast Fourier transform (FFT) algorithm with a properly adjusted sampling rate (which is a function of both the reflector size and the distance from the reflector). The method is validated by comparison with results obtained using surface current and aperture field integration techniques. The performance of several serrated reflectors is evaluated in order to observe the effects of edge diffraction on the test zone fields.

  16. Plane-wave diffraction by a wedge: A spectral domain approach

    NASA Astrophysics Data System (ADS)

    Ciarkowski, A.; Mittra, R.

    1981-11-01

    In this paper we investigate the canonical problem of plane wave diffraction by a wedge in the context of the spectral domain approach which exploits the relationship between the induced current on a scatterer and its far field. We show how the Sommerfeld solution to the wedge diffraction problem can be manipulated in a form which enables one to interpret the far scattered field as the Fourier transform of the physical optics current on the two faces of the wedge, augmented by the fringe current near the tip of the wedge. We also show that the uniform asymptotic expansion derived by Lee and Deschamps on the basis of the Lewis, Ahluwalia and Boersma ansatz can be rigorously obtained using the approach presented in this paper.

  17. Plane wave spectrum treatment of microwave scattering by hydrometeors on an Earth-satellite link

    NASA Astrophysics Data System (ADS)

    Haworth, D. P.

    1980-08-01

    For satellites operating at frequencies above 10 GHz, the effects of propagation through atmospheric hydrometeors are of major importance. In particular, the hydrometeors attenuate, cross polarize and scatter signals causing respectively: a loss in signal level, a decrease in the efficiency of dual polarized channels and station to station interference. For large Earth station antennas operating at high frequencies, the near or Fresnel region of the antenna can extend several kilometers from the antenna and consequently, during disturbed weather, a significant proportion of the hydrometeors affecting propagation are in the near or Fresnel region of the antenna. Previous treatment of propagation through hydrometeors in the Fresnel region of an antenna has proved unsatisfactory and the plane wave spectrum technique was used to accurately characterize antenna scatterer interaction in both the near and far fields of an antenna. The Van de Hulst refractive formula for the coherent propagation and the basis of the radiative transfer equation for the incoherent scattering are derived.

  18. Plane-wave diffraction by a wedge - A spectral domain approach

    NASA Astrophysics Data System (ADS)

    Ciarkowski, A.; Boersma, J.; Mittra, R.

    1984-01-01

    The canonical problem of plane wave diffraction by a wedge in the context of the spectral domain approach which exploits the relationship between the induced current on a scatterer and its far field is investigated. It is shown how the exact solution to the wedge diffraction problem can be manipulated in a form which enables one to interpret the far scattered field as the Fourier transform of the physical optics (PO) current on the two faces of the wedge augmented by the fringe current near the tip of the wedge. A uniform asymptotic expansion for the total field which slightly modifies the Ansatz in the uniform asymptotic theory of electromagnetic edge diffraction is constructed.

  19. LOBSTER: A tool to extract chemical bonding from plane-wave based DFT.

    PubMed

    Maintz, Stefan; Deringer, Volker L; Tchougréeff, Andrei L; Dronskowski, Richard

    2016-04-30

    The computer program LOBSTER (Local Orbital Basis Suite Towards Electronic-Structure Reconstruction) enables chemical-bonding analysis based on periodic plane-wave (PAW) density-functional theory (DFT) output and is applicable to a wide range of first-principles simulations in solid-state and materials chemistry. LOBSTER incorporates analytic projection routines described previously in this very journal [J. Comput. Chem. 2013, 34, 2557] and offers improved functionality. It calculates, among others, atom-projected densities of states (pDOS), projected crystal orbital Hamilton population (pCOHP) curves, and the recently introduced bond-weighted distribution function (BWDF). The software is offered free-of-charge for non-commercial research. © 2016 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc. PMID:26914535

  20. Photoacoustic clutter reduction by inversion of a linear scatter model using plane wave ultrasound measurements

    PubMed Central

    Schwab, Hans-Martin; Beckmann, Martin F.; Schmitz, Georg

    2016-01-01

    Photoacoustic imaging aims to visualize light absorption properties of biological tissue by receiving a sound wave that is generated inside the observed object as a result of the photoacoustic effect. In clinical applications, the strong light absorption in human skin is a major problem. When high amplitude photoacoustic waves that originate from skin absorption propagate into the tissue, they are reflected back by acoustical scatterers and the reflections contribute to the received signal. The artifacts associated with these reflected waves are referred to as clutter or skin echo and limit the applicability of photoacoustic imaging for medical applications severely. This study seeks to exploit the acoustic tissue information gained by plane wave ultrasound measurements with a linear array in order to correct for reflections in the photoacoustic image. By deriving a theory for clutter waves in k-space and a matching inversion approach, photoacoustic measurements compensated for clutter are shown to be recovered. PMID:27446669

  1. Scattering of an electromagnetic plane wave by a Luneburg lens. I. Ray theory.

    PubMed

    Lock, James A

    2008-12-01

    For a plane wave incident on either a Luneburg lens or a modified Luneburg lens, the magnitude and phase of the transmitted electric field are calculated as a function of the scattering angle in the context of ray theory. It is found that the ray trajectory and the scattered intensity are not uniformly convergent in the vicinity of edge ray incidence on a Luneburg lens, which corresponds to the semiclassical phenomenon of orbiting. In addition, it is found that rays transmitted through a large-focal-length modified Luneburg lens participate in a far-zone rainbow, the details of which are exactly analytically soluble in ray theory. Using these results, the Airy theory of the modified Luneburg lens is derived and compared with the Airy theory of the rainbows of a homogeneous sphere. PMID:19037388

  2. Scattering-induced changes in the degree of polarization of a stochastic electromagnetic plane-wave pulse.

    PubMed

    Ding, Chaoliang; Cai, Yangjian; Zhang, Yongtao; Pan, Liuzhan

    2012-06-01

    The scattering of a stochastic electromagnetic plane-wave pulse on a deterministic spherical medium is investigated. An analytical formula for the degree of polarization (DOP) of the scattered field in the far zone is derived. Letting pulse duration T(0) → ∞, our formula can be applied to study the scattering of a stationary stochastic electromagnetic light wave. Numerical results show that the DOP of the far zone field is closely determined by the size of the spherical medium when the incident field is a stochastic electromagnetic plane-wave pulse. This is much different from the case when the incident field is a stationary stochastic electromagnetic light wave, where the DOP of the far zone field is independent of the size of the medium. One may obtain the information of the spherical medium by measuring the scattering-induced changes in the DOP of a stochastic electromagnetic plane-wave pulse.

  3. Plane-wave spectrum approach for the calculation of electromagnetic absorption under near-field exposure conditions.

    PubMed

    Chatterjee, I; Gandhi, O P; Hagmann, M J; Riazi, A

    1980-01-01

    The exposure of humans to electromagnetic near fields has not been sufficiently emphasized by researcher. We have used the plane-wave-spectrum approach to evaluate the electromagnetic field and determine the energy deposited in a lossy, homogeneous, semi-infinite slab placed in the near field of a source leaking radiation. Values of the fields and absorbed energy in the target are obtained by vector summation of the contributions of all the plane waves into which the prescribed field is decomposed. Use of a fast Fourier transform algorithm contributes to the high efficiency of the computations. The numerical results show that, for field distributions that are nearly constant over a physical extent of at least a free-space wavelength, the energy coupled into the target is approximately equal to the resulting from plane-wave exposed.

  4. Plane-wave spectrum approach for the calculation of electromagnetic absorption under near-field exposure conditions

    SciTech Connect

    Chatterjee, I.; Gandhi, O.P.; Hagmann, M.J.; Riazi, A.

    1980-01-01

    The exposure of humans to electromagnetic near fields has not been sufficiently emphasized by researcher. We have used the plane-wave-spectrum approach to evaluate the electromagnetic field and determine the energy deposited in a lossy, homogeneous, semi-infinite slab placed in the near field of a source leaking radiation. Values of the fields and absorbed energy in the target are obtained by vector summation of the contributions of all the plane waves into which the prescribed field is decomposed. Use of a fast Fourier transform algorithm contributes to the high efficiency of the computations. The numerical results show that, for field distributions that are nearly constant over a physical extent of at least a free-space wavelength, the energy coupled into the target is approximately equal to the resulting from plane-wave exposed.

  5. Nonlinear Breit-Wheeler process in the collision of a photon with two plane waves

    NASA Astrophysics Data System (ADS)

    Wu, Yuan-Bin; Xue, She-Sheng

    2014-07-01

    The nonlinear Breit-Wheeler process of electron-positron pair production off a probe photon colliding with a low-frequency and a high-frequency electromagnetic wave that propagate in the same direction is analyzed. We calculate the pair-production probability and the spectra of the created pair in the nonlinear Breit-Wheeler processes of pair production off a probe photon colliding with two plane waves or one of these two plane waves. The differences of these two cases are discussed. We evidently show, in the two-wave case, the possibility of Breit-Wheeler pair production with simultaneous photon emission into the low-frequency wave and the high multiphoton phenomena: (i) Breit-Wheeler pair production by absorption of the probe photon and a large number of photons from the low-frequency wave, in addition to the absorption of one photon from the high-frequency wave; (ii) Breit-Wheeler pair production by absorption of the probe photon and one photon from the high-frequency wave with simultaneous emission of a large number of photons into the low-frequency wave. The phenomenon of photon emission into the wave cannot happen in the one-wave case. Compared with the one-wave case, the contributions from high multiphoton processes are largely enhanced in the two-wave case. The results presented in this article show a possible way to access the observations of the phenomenon of photon emission into the wave and high multiphoton phenomenon in Breit-Wheeler pair production even with the laser-beam intensity of order 1018 W/cm2.

  6. Plane waves at or near grazing incidence in the parabolic approximation. [acoustic equations of motion for sound fields

    NASA Technical Reports Server (NTRS)

    Mcaninch, G. L.; Myers, M. K.

    1980-01-01

    The parabolic approximation for the acoustic equations of motion is applied to the study of the sound field generated by a plane wave at or near grazing incidence to a finite impedance boundary. It is shown how this approximation accounts for effects neglected in the usual plane wave reflection analysis which, at grazing incidence, erroneously predicts complete cancellation of the incident field by the reflected field. Examples are presented which illustrate that the solution obtained by the parabolic approximation contains several of the physical phenomena known to occur in wave propagation near an absorbing boundary.

  7. Analytical expressions for the log-amplitude correlation function for plane wave propagation in anisotropic non-Kolmogorov refractive turbulence.

    PubMed

    Gudimetla, V S Rao; Holmes, Richard B; Riker, Jim F

    2012-12-01

    An analytical expression for the log-amplitude correlation function for plane wave propagation through anisotropic non-Kolmogorov turbulent atmosphere is derived. The closed-form analytic results are based on the Rytov approximation. These results agree well with wave optics simulation based on the more general Fresnel approximation as well as with numerical evaluations, for low-to-moderate strengths of turbulence. The new expression reduces correctly to the previously published analytic expressions for the cases of plane wave propagation through both nonisotropic Kolmogorov turbulence and isotropic non-Kolmogorov turbulence cases. These results are useful for understanding the potential impact of deviations from the standard isotropic Kolmogorov spectrum.

  8. Generalized Debye series expansion of electromagnetic plane wave scattering by an infinite multilayered cylinder at oblique incidence.

    PubMed

    Li, Renxian; Han, Xiang'e; Ren, Kuan Fang

    2009-03-01

    The Debye series expansion expresses the Mie scattering coefficients into a series of Fresnel coefficients and gives physical interpretation of different scattering modes, but when an infinite multilayered cylinder is obliquely illuminated by electromagnetic plane waves, the scattering process becomes very complicated because of cross polarization. Based on the relation of boundary conditions between global scattering process and local scattering processes, the generalized Debye series expansion of plane wave scattering by an infinite multilayered cylinder at oblique incidence is derived in this paper. The formula and the code are verified by the comparison of the results with that of Lorenz-Mie theory in special cases and those presented in the literatures.

  9. Plane-wave scattering by self-complementary metasurfaces in terms of electromagnetic duality and Babinet's principle

    NASA Astrophysics Data System (ADS)

    Nakata, Yosuke; Urade, Yoshiro; Nakanishi, Toshihiro; Kitano, Masao

    2013-11-01

    We investigate theoretically electromagnetic plane-wave scattering by self-complementary metasurfaces. By using Babinet's principle extended to metasurfaces with resistive elements, we show that the frequency-independent transmission and reflection are realized for normal incidence of a circularly polarized plane wave onto a self-complementary metasurface, even if there is diffraction. Next, we consider two special classes of self-complementary metasurfaces. We show that self-complementary metasurfaces with rotational symmetry can act as coherent perfect absorbers, and those with translational symmetry compatible with their self-complementarity can split the incident power equally, even for oblique incidences.

  10. Strong scintillations of a plane wave in a medium with a spectrum of Gaussian-type irregularities

    NASA Astrophysics Data System (ADS)

    Shishov, V. I.

    The solution of an equation for the fourth moment of the field of a plane wave propagating in a statistically irregular medium is investigated analytically. Particular emphasis is placed on the strong-focusing regime. Asymptotic expressions are obtained for the scintillation spectrum and index in the regimes of strong focusing and scintillation saturation.

  11. A projection-free method for representing plane-wave DFT results in an atom-centered basis

    SciTech Connect

    Dunnington, Benjamin D.; Schmidt, J. R.

    2015-09-14

    Plane wave density functional theory (DFT) is a powerful tool for gaining accurate, atomic level insight into bulk and surface structures. Yet, the delocalized nature of the plane wave basis set hinders the application of many powerful post-computation analysis approaches, many of which rely on localized atom-centered basis sets. Traditionally, this gap has been bridged via projection-based techniques from a plane wave to atom-centered basis. We instead propose an alternative projection-free approach utilizing direct calculation of matrix elements of the converged plane wave DFT Hamiltonian in an atom-centered basis. This projection-free approach yields a number of compelling advantages, including strict orthonormality of the resulting bands without artificial band mixing and access to the Hamiltonian matrix elements, while faithfully preserving the underlying DFT band structure. The resulting atomic orbital representation of the Kohn-Sham wavefunction and Hamiltonian provides a gateway to a wide variety of analysis approaches. We demonstrate the utility of the approach for a diverse set of chemical systems and example analysis approaches.

  12. ABINIT: Plane-Wave-Based Density-Functional Theory on High Performance Computers

    NASA Astrophysics Data System (ADS)

    Torrent, Marc

    2014-03-01

    For several years, a continuous effort has been produced to adapt electronic structure codes based on Density-Functional Theory to the future computing architectures. Among these codes, ABINIT is based on a plane-wave description of the wave functions which allows to treat systems of any kind. Porting such a code on petascale architectures pose difficulties related to the many-body nature of the DFT equations. To improve the performances of ABINIT - especially for what concerns standard LDA/GGA ground-state and response-function calculations - several strategies have been followed: A full multi-level parallelisation MPI scheme has been implemented, exploiting all possible levels and distributing both computation and memory. It allows to increase the number of distributed processes and could not be achieved without a strong restructuring of the code. The core algorithm used to solve the eigen problem (``Locally Optimal Blocked Congugate Gradient''), a Blocked-Davidson-like algorithm, is based on a distribution of processes combining plane-waves and bands. In addition to the distributed memory parallelization, a full hybrid scheme has been implemented, using standard shared-memory directives (openMP/openACC) or porting some comsuming code sections to Graphics Processing Units (GPU). As no simple performance model exists, the complexity of use has been increased; the code efficiency strongly depends on the distribution of processes among the numerous levels. ABINIT is able to predict the performances of several process distributions and automatically choose the most favourable one. On the other hand, a big effort has been carried out to analyse the performances of the code on petascale architectures, showing which sections of codes have to be improved; they all are related to Matrix Algebra (diagonalisation, orthogonalisation). The different strategies employed to improve the code scalability will be described. They are based on an exploration of new diagonalization

  13. Investigation of damping and radiation using full plane wave decomposition in ducts

    NASA Astrophysics Data System (ADS)

    Allam, Sabry; Åbom, Mats

    2006-05-01

    A general plane wave decomposition procedure that determines both the wave amplitudes (or the reflection coefficient) and the wavenumbers is proposed for in-duct measurements. To improve the quality of the procedure, overdetermination and a nonlinear least-squares procedure is used. The procedure has been tested using a six microphone array, and used for accurate measurements of the radiation from an open unflanged pipe with flow. The experimental results for the reflection coefficient magnitude and the end correction have been compared with the theory of Munt. The agreement is very good if the maximum speed rather than the average is used to compare measurements and theory. This result is the first complete experimental validation of the theory of Munt [Acoustic transmission properties of a jet pipe with subsonic jet flow, I: the cold jet reflection coefficient, Journal of Sound and Vibration 142(3) (1990) 413-436]. The damping of the plane wave (the imaginary part of the wavenumber) could also be obtained from the experimental data. It is found that the damping increases strongly, compared with the damping for a quiescent fluid, when the acoustic boundary layer becomes thicker than the viscous sublayer. This finding is in agreement with a few earlier measurements and is also in agreement with a theoretical model proposed by Howe [The damping of sound by wall turbulent sheer layers, Journal of Acoustic Society of America 98(3) (1995) 1723-1730]. The results reported here are the first experimental verifications of Howe's model. It is found that the model works well typically up to a normalized acoustic boundary layer thickness δA+ of 30-40. For values of a δA+ less than 10, corresponding to higher frequencies or lower flow speeds, the model proposed by Dokumaci [A note on transmission of sound in a wide pipe with mean flow and viscothermal attenuation, Journal of Sound and Vibration 208(4) (1997) 653-655] is also in good agreement with the experimental data.

  14. The strain in the array is mainly in the plane (waves below ~1 Hz)

    USGS Publications Warehouse

    Gomberg, J.; Pavlis, G.; Bodin, P.

    1999-01-01

    We compare geodetic and single-station methods of measuring dynamic deformations and characterize their causes in the frequency bands 0.5-1.0 Hz and 4.0-8.0 Hz. The geodetic approach utilizes data from small-aperture seismic arrays, applying techniques from geodesy. It requires relatively few assumptions and a priori information. The single-station method uses ground velocities recorded at isolated or single stations and assumes all the deformation is due to plane-wave propagation. It also requires knowledge of the azimuth and horizontal velocity of waves arriving at the recording station. Data employed come from a small-aperture, dense seismic array deployed in Geyokcha, Turkmenistan, and include seismograms recorded by broadband STS2 and short-period L28 sensors. Poor agreement between geodetic and single-station estimates in the 4.0-8.0 Hz passband indicates that the displacement field may vary nonlinearly with distance over distances of ~50 m. STS2 geodetic estimates provide a robust standard in the 0.5-1.0 Hz passband because they appear to be computationally stable and require fewer assumptions than single-station estimates. The agreement between STS2 geodetic estimates and single-station L28 estimates is surprisingly good for the S-wave and early surface waves, suggesting that the single-station analysis should be useful with commonly available data. These results indicate that, in the 0.5 to 1.0 Hz passband, the primary source of dynamic deformation is plane-wave propagation along great-circle source-receiver paths. For later arriving energy, the effects of scattering become important. The local structure beneath the array exerts a strong control on the geometry of the dynamic deformation, implying that it may be difficult to infer source characteristics of modern or paleoearthquakes from indicators of dynamic deformations. However, strong site control also suggests that the dynamic deformations may be predictable, which would be useful for engineering

  15. Plane Wave First-principles Materials Science Codes on Multicore Supercomputer Architectures

    NASA Astrophysics Data System (ADS)

    Canning, Andrew; Deslippe, Jack; Louie, Steven. G.; Scidac Team

    2014-03-01

    Plane wave first-principles codes based on 3D FFTs are one of the largest users of supercomputer cycles in the world. Modern supercomputer architectures are constructed from chips having many CPU cores with nodes containing multiple chips. Designs for future supercomputers are projected to have even more cores per chip. I will present new developments for hybrid MPI/OpenMP PW codes focusing on a specialized 3D FFTs that gives greatly improved scaling over a pure MPI version on multicore machines. Scaling results will be presented for the full electronic structure codes PARATEC and BerkeleyGW. using the new hybrid 3D FFTs, threaded libraries and OpenMP to gain greatly improved scaling to very large core count on Cray and IBM machines. Support for this work was provided through the Scientific Discovery through Advanced Computing (SciDAC) program funded by U.S. Department of Energy, Office of Science, Advanced Scientific Computing Research (and Basic Energy Sciences).

  16. Reconstruction of nonstationary sound fields based on the time domain plane wave superposition method.

    PubMed

    Zhang, Xiao-Zheng; Thomas, Jean-Hugh; Bi, Chuan-Xing; Pascal, Jean-Claude

    2012-10-01

    A time-domain plane wave superposition method is proposed to reconstruct nonstationary sound fields. In this method, the sound field is expressed as a superposition of time convolutions between the estimated time-wavenumber spectrum of the sound pressure on a virtual source plane and the time-domain propagation kernel at each wavenumber. By discretizing the time convolutions directly, the reconstruction can be carried out iteratively in the time domain, thus providing the advantage of continuously reconstructing time-dependent pressure signals. In the reconstruction process, the Tikhonov regularization is introduced at each time step to obtain a relevant estimate of the time-wavenumber spectrum on the virtual source plane. Because the double infinite integral of the two-dimensional spatial Fourier transform is discretized directly in the wavenumber domain in the proposed method, it does not need to perform the two-dimensional spatial fast Fourier transform that is generally used in time domain holography and real-time near-field acoustic holography, and therefore it avoids some errors associated with the two-dimensional spatial fast Fourier transform in theory and makes possible to use an irregular microphone array. The feasibility of the proposed method is demonstrated by numerical simulations and an experiment with two speakers.

  17. Plane-wave transverse oscillation for high-frame-rate 2-D vector flow imaging.

    PubMed

    Lenge, Matteo; Ramalli, Alessandro; Tortoli, Piero; Cachard, Christian; Liebgott, Hervé

    2015-12-01

    Transverse oscillation (TO) methods introduce oscillations in the pulse-echo field (PEF) along the direction transverse to the ultrasound propagation direction. This may be exploited to extend flow investigations toward multidimensional estimates. In this paper, the TOs are coupled with the transmission of plane waves (PWs) to reconstruct high-framerate RF images with bidirectional oscillations in the pulse-echo field. Such RF images are then processed by a 2-D phase-based displacement estimator to produce 2-D vector flow maps at thousands of frames per second. First, the capability of generating TOs after PW transmissions was thoroughly investigated by varying the lateral wavelength, the burst length, and the transmission frequency. Over the entire region of interest, the generated lateral wavelengths, compared with the designed ones, presented bias and standard deviation of -3.3 ± 5.7% and 10.6 ± 7.4% in simulations and experiments, respectively. The performance of the ultrafast vector flow mapping method was also assessed by evaluating the differences between the estimated velocities and the expected ones. Both simulations and experiments show overall biases lower than 20% when varying the beam-to-flow angle, the peak velocity, and the depth of interest. In vivo applications of the method on the common carotid and the brachial arteries are also presented. PMID:26670852

  18. Underdetermined system theory applied to quantitative analysis of responses caused by unsteady smooth-plane waves

    NASA Astrophysics Data System (ADS)

    Sano, Yukio

    1993-01-01

    The mechanical responses of rate-dependent media caused by unsteady smooth-plane waves are quantitatively analyzed by an underdetermined system of equations without using any constitutive relation of the media; that is, by using the particle velocity field expressed by an algebraic equation that is derived from the mass conservation equation, and the stress field expressed by an algebraic equation that is derived from the momentum conservation equation. First of all, this approach for analyzing unsteady wave motion is justified by the verification of various inferences such as the existence of the nonindependent elementary waves by Sano [J. Appl. Phys. 65, 3857(1989)] and the degradation process by Sano [J. Appl. Phys. 67, 4072(1990)]. Second, the situation under which a spike arises in particle velocity-time and stress-time profiles, and the reason for the arising are clarified. Third, the influence of the spike on stress-particle velocity and stress-strain paths is examined. The spike induced in the profiles by a growing wave greatly influences the paths near the impacted surface. Finally, calculated particle velocity-time profiles are compared with experimental data.

  19. Kinetic theory of electromagnetic plane wave obliquely incident on bounded plasma slab

    SciTech Connect

    Angus, J. R.; Krasheninnikov, S. I.; Smolyakov, A. I.

    2010-10-15

    The effects of electromagnetic plane waves obliquely incident on a warm bounded plasma slab of finite length L are studied by solving the coupled Vlasov-Maxwell set of equations. It is shown that the solution can be greatly simplified in the limit where thermal effects are most important by expanding in small parameters and introducing self-similar variables. These solutions reveal that the coupling of thermal effects with the angle of incidence is negligible in the region of bounce resonance and anomalous skin effect. In the region of the anomalous skin effect, the heating is shown to scale linearly with the anomalous skin depth {delta}{sub a} when {delta}{sub a}<>L, the heating is shown to decay with 1/{delta}{sub a}{sup 3}. The transmission is found to be exponentially larger than that predicted from a local theory in the appropriate region of the anomalous skin effect.

  20. Performance bounds for passive sensor arrays operating in a turbulent medium: plane-wave analysis.

    PubMed

    Collier, S L; Wilson, D K

    2003-05-01

    The performance bounds of a passive acoustic array operating in a turbulent medium with fluctuations described by a von Kármán spectrum are investigated. This treatment considers a single, monochromatic, plane-wave source at near-normal incidence. A line-of-sight propagation path is assumed. The primary interests are in calculating the Cramer-Rao lower bounds of the azimuthal and elevational angles of arrival and in observing how these bounds change with the introduction of additional unknowns, such as the propagation distance, turbulence parameters, and signal-to-noise ratio. In both two and three dimensions, it is found that for large values of the index-of-refraction variance, the Cramer-Rao lower bounds of the angles of arrival increase significantly at large values of the normalized propagation distance. For small values of the index-of-refraction variance and normalized propagation distance, the signal-to-noise ratio is found to be the limiting factor. In the two-dimensional treatment, it is found that the estimate of the angle of arrival will decouple from the estimates of the other parameters with the appropriate choice of array geometry. In three dimensions, again with an appropriate choice of array geometry, the estimates of the azimuth and elevation will decouple from the estimates of the other parameters, but due to the constraints of the model, will remain coupled to one another.

  1. Simultaneous quantification of flow and tissue velocities based on multi-angle plane wave imaging.

    PubMed

    Ekroll, Ingvild Kinn; Swillens, Abigail; Segers, Patrick; Dahl, Torbjørn; Torp, Hans; Lovstakken, Lasse

    2013-04-01

    A quantitative angle-independent 2-D modality for flow and tissue imaging based on multi-angle plane wave acquisition was evaluated. Simulations of realistic flow in a carotid artery bifurcation were used to assess the accuracy of the vector Doppler (VD) technique. Reduction in root mean square deviation from 27 cm/s to 6 cm/s and 7 cm/s to 2 cm/s was found for the lateral (vx) and axial (vz) velocity components, respectively, when the ensemble size was increased from 8 to 50. Simulations of a Couette flow phantom (vmax = 2.7 cm/s) gave promising results for imaging of slowly moving tissue, with root mean square deviation of 4.4 mm/s and 1.6 mm/s for the x- and z-components, respectively. A packet acquisition scheme providing both B-mode and vector Doppler RF data was implemented on a research scanner, and beamforming and further post-processing was done offline. In vivo results of healthy volunteers were in accordance with simulations and gave promising results for flow and tissue vector velocity imaging. The technique was also tested in patients with carotid artery disease. Using the high ensemble vector Doppler technique, blood flow through stenoses and secondary flow patterns were better visualized than in ordinary color Doppler. Additionally, the full velocity spectrum could be obtained retrospectively for arbitrary points in the image.

  2. A Plane-Wave Implementation of Quasiparticle Self-Consistent GW (QSGW)

    NASA Astrophysics Data System (ADS)

    Vigil Currey, Derek; Deslippe, Jack; Louie, Steven G.

    2011-03-01

    The use of GW techniques in calculating the quasiparticle properties of certain classes of materials, e.g. complex oxides, is sometimes hindered by the poor mean-field starting point that density functional theory (DFT) within standard Kohn-Sham implementations provides. There has been considerable effort in the community to improve upon the mean-field starting point for a broad range of materials. A recently proposed method, the quasiparticle self-consistent GW (QSGW) method, employs a process in which a mean-field exchange-correlation potential is approximated from and updated self-consistently using the self-energy operator from previous iteration GW calculations. We present an implementation of this method in a plane-wave basis, and discuss its accuracy, computational cost, and physical implications for a variety of semiconducting materials. This work was supported by NSF Grant No. DMR10-1006184 and U.S. DOE Contract No. DE-AC02-05CH11231. Computational resources were provided by NERSC. Derek Vigil Currey acknowledges funding from UC-Berkeley through the Chancellor's Fellowship.

  3. Formulation of the Augmented Plane-Wave and Muffin-Tin Orbital Method

    NASA Astrophysics Data System (ADS)

    Kotani, Takao; Kino, Hiori; Akai, Hisazumu

    2015-03-01

    The augmented plane waves and the muffin-tin orbitals method (the PMT method) was proposed by Kotani and van Schilfgaarde in Phys. Rev. B 81, 125117 (2010). It is a mixed basis all-electron full-potential method, which uses two types of augmented waves simultaneously, in addition to the local orbitals. In this paper, this mixed basis method is reformulated on the basis of a new formalism named as the 3-component formalism, which is a mathematically transparent version of the additive augmentation originally proposed by Soler and Williams in Phys. Rev. B 47, 6784 (1993). Atomic forces are easily derived systematically. We discuss some problems in the mixed basis method and ways to manage them. In addition, we compare the method with the PAW method on the same footing. This PMT method is the basis for our new development of the quasiparticle self-consistent GW method in J. Phys. Soc. Jpn. 83, 094711 (2014), available as the ecalj package at github.

  4. Plane wave expansion method used to engineer photonic crystal sensors with high efficiency.

    PubMed

    Antos, Roman; Vozda, Vojtech; Veis, Martin

    2014-02-10

    A photonic crystal waveguide (PhC-WG) was reported to be usable as an optical sensor highly sensitive to various material parameters, which can be detected via changes in transmission through the PhC-WG caused by small changes of the refractive index of the medium filling its holes. To monitor these changes accurately, a precise optical model is required, for which the plane wave expansion (PWE) method is convenient. We here demonstrate the revision of the PWE method by employing the complex Fourier factorization approach, which enables the calculation of dispersion diagrams with fast convergence, i.e., with high precision in relatively short time. The PhC-WG is proposed as a line defect in a hexagonal array of cylindrical holes periodically arranged in bulk silicon, filled with a variable medium. The method of monitoring the refractive index changes is based on observing cutoff wavelengths in the PhC-WG dispersion diagrams. The PWE results are also compared with finite-difference time-domain calculations of transmittance carried out on a PhC-WG with finite dimensions. PMID:24663549

  5. Enhanced acoustic transmission into dissipative solid materials through the use of inhomogeneous plane waves

    NASA Astrophysics Data System (ADS)

    Woods, D. C.; Bolton, J. S.; Rhoads, J. F.

    2016-09-01

    A number of applications, for instance ultrasonic imaging and nondestructive testing, involve the transmission of acoustic energy across fluid-solid interfaces into dissipative solids. However, such transmission is generally hindered by the large impedance mismatch at the interface. In order to address this problem, inhomogeneous plane waves were investigated in this work for the purpose of improving the acoustic energy transmission. To this end, under the assumption of linear hysteretic damping, models for fluid-structure interaction were developed that allow for both homogeneous and inhomogeneous incident waves. For low-loss solids, the results reveal that, at the Rayleigh angle, a unique value of the wave inhomogeneity can be found which minimizes the reflection coefficient, and consequently maximizes the transmission. The results also reveal that with sufficient dissipation levels in the solid material, homogeneous incident waves yield lower reflection values than inhomogeneous waves, due to the large degrees of inhomogeneity inherent in the transmitted waves. Analytical conditions have also been derived which predict the dependence of the optimal incident wave type on the dissipation level and wave speeds in the solid medium. Finally, implications related to the use of acoustic beams of limited spatial extent are discussed.

  6. Plane wave expansion method used to engineer photonic crystal sensors with high efficiency.

    PubMed

    Antos, Roman; Vozda, Vojtech; Veis, Martin

    2014-02-10

    A photonic crystal waveguide (PhC-WG) was reported to be usable as an optical sensor highly sensitive to various material parameters, which can be detected via changes in transmission through the PhC-WG caused by small changes of the refractive index of the medium filling its holes. To monitor these changes accurately, a precise optical model is required, for which the plane wave expansion (PWE) method is convenient. We here demonstrate the revision of the PWE method by employing the complex Fourier factorization approach, which enables the calculation of dispersion diagrams with fast convergence, i.e., with high precision in relatively short time. The PhC-WG is proposed as a line defect in a hexagonal array of cylindrical holes periodically arranged in bulk silicon, filled with a variable medium. The method of monitoring the refractive index changes is based on observing cutoff wavelengths in the PhC-WG dispersion diagrams. The PWE results are also compared with finite-difference time-domain calculations of transmittance carried out on a PhC-WG with finite dimensions.

  7. Plane-wave Fresnel diffraction by elliptic apertures: a Fourier-based approach.

    PubMed

    Borghi, Riccardo

    2014-10-01

    A simple theoretical approach to evaluate the scalar wavefield, produced, within paraxial approximation, by the diffraction of monochromatic plane waves impinging on elliptic apertures or obstacles is presented. We find that the diffracted field can be mathematically described in terms of a Fourier series with respect to an angular variable suitably related to the elliptic parametrization of the observation plane. The convergence features of such Fourier series are analyzed, and a priori truncation criterion is also proposed. Two-dimensional maps of the optical intensity diffraction patterns are then numerically generated and compared, at a visual level, with several experimental pictures produced in the past. The last part of this work is devoted to carrying out an analytical investigation of the diffracted field along the ellipse axis. A uniform approximation is derived on applying a method originally developed by Schwarzschild, and an asymptotic estimate, valid in the limit of small eccentricities, is also obtained via the Maggi-Rubinowicz boundary wave theory. PMID:25401234

  8. On plane-wave relativistic electrodynamics in plasmas and in vacuum

    NASA Astrophysics Data System (ADS)

    Fiore, Gaetano

    2014-06-01

    We revisit the exact microscopic equations (in differential, and equivalent integral form) ruling a relativistic cold plasma after the plane-wave Ansatz, without customary approximations. We show that in the Eulerian description the motion of a very diluted plasma initially at rest and excited by an arbitrary transverse plane electromagnetic travelling-wave has a very simple and explicit dependence on the transverse electromagnetic potential; for a non-zero density plasma the above motion is a good approximation of the real one as long as the back-reaction of the charges on the electromagnetic field can be neglected, i.e. for a time lapse decreasing with the plasma density, and can be used as initial step in an iterative resolution scheme. As one of many possible applications, we use these results to describe how the ponderomotive force of a very intense and short plane laser pulse hitting normally the surface of a plasma boosts the surface electrons into the ion background. In response to this penetration, the electrons are pulled back by the electric force exerted by the ions and the other displaced electrons and may leave the plasma with high energy in the direction opposite to that of propagation of the pulse ‘slingshot effect’ (Fiore G et al 2013 arXiv:1309.1400).

  9. On the formation of shocks of electromagnetic plane waves in non-linear crystals

    NASA Astrophysics Data System (ADS)

    Christodoulou, Demetrios; Perez, Daniel Raoul

    2016-08-01

    An influential result of F. John states that no genuinely non-linear strictly hyperbolic quasi-linear first order system of partial differential equations in two variables has a global C2-solution for small enough initial data. Inspired by recent work of D. Christodoulou, we revisit John's original proof and extract a more precise description of the behaviour of solutions at the time of shock. We show that John's singular first order quantity, when expressed in characteristic coordinates, remains bounded until the final time, which is then characterised by an inverse density of characteristics tending to zero in one point. Moreover, we study the derivatives of second order, showing again their boundedness when expressed in appropriate coordinates. We also recover John's upper bound for the time of shock formation and complement it with a lower bound. Finally, we apply these results to electromagnetic plane waves in a crystal with no magnetic properties and cubic electric non-linearity in the energy density, assuming no dispersion.

  10. Numerical modeling of undersea acoustics using a partition of unity method with plane waves enrichment

    NASA Astrophysics Data System (ADS)

    Hospital-Bravo, Raúl; Sarrate, Josep; Díez, Pedro

    2016-05-01

    A new 2D numerical model to predict the underwater acoustic propagation is obtained by exploring the potential of the Partition of Unity Method (PUM) enriched with plane waves. The aim of the work is to obtain sound pressure level distributions when multiple operational noise sources are present, in order to assess the acoustic impact over the marine fauna. The model takes advantage of the suitability of the PUM for solving the Helmholtz equation, especially for the practical case of large domains and medium frequencies. The seawater acoustic absorption and the acoustic reflectance of the sea surface and sea bottom are explicitly considered, and perfectly matched layers (PML) are placed at the lateral artificial boundaries to avoid spurious reflexions. The model includes semi-analytical integration rules which are adapted to highly oscillatory integrands with the aim of reducing the computational cost of the integration step. In addition, we develop a novel strategy to mitigate the ill-conditioning of the elemental and global system matrices. Specifically, we compute a low-rank approximation of the local space of solutions, which in turn reduces the number of degrees of freedom, the CPU time and the memory footprint. Numerical examples are presented to illustrate the capabilities of the model and to assess its accuracy.

  11. Full waveform inversion of marine reflection data in the plane-wave domain

    SciTech Connect

    Minkoff, S.E.; Symes, W.W.

    1997-03-01

    Full waveform inversion of a p-{tau} marine data set from the Gulf of Mexico provides estimates of the long-wavelength P-wave background velocity, anisotropic seismic source, and three high-frequency elastic parameter reflectivities that explain 70% of the total seismic data and 90% of the data in an interval around the gas sand target. The forward simulator is based on a plane-wave viscoelastic model for P-wave propagation and primary reflections in a layered earth. Differential semblance optimization, a variant of output least-squares inversion, successfully estimates the nonlinear P-wave background velocity and linear reflectivities. Once an accurate velocity is estimated, output least-squares inversion reestimates the reflectivities and an anisotropic seismic source simultaneously. The viscoelastic model predicts the amplitude-versus-angle trend in the data more accurately than does an elastic model. Simultaneous inversion for reflectivities and source explains substantially more of the actual data than does inversion for reflectivities with fixed source from an air-gun modeler. The best reflectivity estimates conform to widely accepted lithologic relationships and closely match the filtered well logs.

  12. Calculation of VLEED spectra with the extended linear augmented plane wave kp method

    NASA Astrophysics Data System (ADS)

    Krasovskii, E. E.; Schattke, W.

    1999-11-01

    We describe a new method to calculate the VLEED (very low energy electron diffraction) spectra within the Bloch waves approach. The method is based on the variational solution of the Schrödinger equation for a semi-infinite crystal. Inside the solid the trial LEED function Φ is a linear combination of propagating and evanescent Bloch waves, which are generated by the inverse ELAPW (extended linear augmented plane waves)-kp method. The trial function is smoothly continuous over the whole space, and it satisfies by construction the equation ( Ĥ - E) Φ=0 both in the crystal and in the vacuum half-spaces. In the surface layer the equation δ‖( Ĥ - E) Φ‖=0 is solved. To illustrate the properties of the method we discuss its application to the 1D case. We have performed a self-consistent band structure calculation of the 1 T chalcogenide VSe2 and obtained from the first principles the normal-incidence target current spectrum (TCS) for its (0001) surface.

  13. Dynamical cluster approximation within an augmented plane wave framework: Spectral properties of SrVO3

    NASA Astrophysics Data System (ADS)

    Lee, Hunpyo; Foyevtsova, Kateryna; Ferber, Johannes; Aichhorn, Markus; Jeschke, Harald O.; Valentí, Roser

    2012-04-01

    We present a combination of local-density approximation (LDA) with the dynamical cluster approximation (LDA+DCA) in the framework of the full-potential linear augmented plane wave method, and compare our LDA+DCA results for SrVO3 to LDA with the dynamical mean-field theory (LDA+DMFT) calculations as well as experimental observations on SrVO3. We find a qualitative agreement of the momentum resolved spectral function with angle-resolved photoemission spectra (ARPES) and former LDA+DMFT results. As a correction to LDA+DMFT, we observe more pronounced coherent peaks below the Fermi level, as indicated by ARPES experiments. In addition, we resolve the spectral functions in the K0=(0,0,0) and K1=(π,π,π) sectors of DCA, where band insulating and metallic phases coexist. Our approach can be applied to correlated compounds where not only local quantum fluctuations but also spatial fluctuations are important.

  14. Near-field coupling model between PCB and grounded transmission line based on plane wave spectrum

    NASA Astrophysics Data System (ADS)

    Leseigneur, Christelle; Baudry, David; Ravelo, Blaise; Louis, Anne

    2013-10-01

    This article presents an explicit model of electromagnetic (EM) coupling between electronic circuits and metallic wire placed above the ground plane. The model is based on the interaction between the EM near-field (NF) that has been treated with plane wave spectrum (PWS) and the Taylor model. The routine process illustrating the methodology is addressed is this article. The practicability of the model developed was upheld with different analytical and real demonstrators. First, the NF coupling between a straight transmission line (TL) and 1 GHz Wilkinson power divider (PWD) designed and implemented in planar technology was provided. Subsequently, simulations with a powerful commercial tool and measurements from 0.2 GHz to 2 GHz revealed a good agreement between the coupling voltages from the proposed model. As a second proof of concept, a printed circuit board incorporating a 40 MHz RF oscillator was placed 5 mm above the grounded TL. Once again, coupling voltages matched measurements were observed with magnitude relative difference lower than 5 dB. The hereby model presents huge benefits not only in terms of flexibility in the design process but it can also be run with very less computation time compared to the existing standard simulators. The model can be potentially a good candidate for investigating complex systems EMC engineering.

  15. Performance bounds for passive sensor arrays operating in a turbulent medium: Plane-wave analysis

    NASA Astrophysics Data System (ADS)

    Collier, S. L.; Wilson, D. K.

    2003-05-01

    The performance bounds of a passive acoustic array operating in a turbulent medium with fluctuations described by a von Kármán spectrum are investigated. This treatment considers a single, monochromatic, plane-wave source at near-normal incidence. A line-of-sight propagation path is assumed. The primary interests are in calculating the Cramer-Rao lower bounds of the azimuthal and elevational angles of arrival and in observing how these bounds change with the introduction of additional unknowns, such as the propagation distance, turbulence parameters, and signal-to-noise ratio. In both two and three dimensions, it is found that for large values of the index-of-refraction variance, the Cramer-Rao lower bounds of the angles of arrival increase significantly at large values of the normalized propagation distance. For small values of the index-of-refraction variance and normalized propagation distance, the signal-to-noise ratio is found to be the limiting factor. In the two-dimensional treatment, it is found that the estimate of the angle of arrival will decouple from the estimates of the other parameters with the appropriate choice of array geometry. In three dimensions, again with an appropriate choice of array geometry, the estimates of the azimuth and elevation will decouple from the estimates of the other parameters, but due to the constraints of the model, will remain coupled to one another.

  16. Scaling of plane-wave functions in statistically optimized near-field acoustic holography.

    PubMed

    Hald, Jørgen

    2014-11-01

    Statistically Optimized Near-field Acoustic Holography (SONAH) is a Patch Holography method, meaning that it can be applied in cases where the measurement area covers only part of the source surface. The method performs projections directly in the spatial domain, avoiding the use of spatial discrete Fourier transforms and the associated errors. First, an inverse problem is solved using regularization. For each calculation point a multiplication must then be performed with two transfer vectors--one to get the sound pressure and the other to get the particle velocity. Considering SONAH based on sound pressure measurements, existing derivations consider only pressure reconstruction when setting up the inverse problem, so the evanescent wave amplification associated with the calculation of particle velocity is not taken into account in the regularized solution of the inverse problem. The present paper introduces a scaling of the applied plane wave functions that takes the amplification into account, and it is shown that the previously published virtual source-plane retraction has almost the same effect. The effectiveness of the different solutions is verified through a set of simulated measurements. PMID:25373969

  17. Plane wave holonomies in quantum gravity. II. A sine wave solution

    NASA Astrophysics Data System (ADS)

    Neville, Donald E.

    2015-08-01

    This paper constructs an approximate sinusoidal wave packet solution to the equations of canonical gravity. The theory uses holonomy-flux variables with support on a lattice (LHF =lattice-holonomy flux ). There is an SU(2) holonomy on each edge of the LHF simplex, and the goal is to study the behavior of these holonomies under the influence of a passing gravitational wave. The equations are solved in a small sine approximation: holonomies are expanded in powers of sines and terms beyond sin2 are dropped; also, fields vary slowly from vertex to vertex. The wave is unidirectional and linearly polarized. The Hilbert space is spanned by a set of coherent states tailored to the symmetry of the plane wave case. Fixing the spatial diffeomorphisms is equivalent to fixing the spatial interval between vertices of the loop quantum gravity lattice. This spacing can be chosen such that the eigenvalues of the triad operators are large, as required in the small sine limit, even though the holonomies are not large. Appendices compute the energy of the wave, estimate the lifetime of the coherent state packet, discuss circular polarization and coarse-graining, and determine the behavior of the spinors used in the U(N) SHO realization of LQG.

  18. Plane-wave transverse oscillation for high-frame-rate 2-D vector flow imaging.

    PubMed

    Lenge, Matteo; Ramalli, Alessandro; Tortoli, Piero; Cachard, Christian; Liebgott, Hervé

    2015-12-01

    Transverse oscillation (TO) methods introduce oscillations in the pulse-echo field (PEF) along the direction transverse to the ultrasound propagation direction. This may be exploited to extend flow investigations toward multidimensional estimates. In this paper, the TOs are coupled with the transmission of plane waves (PWs) to reconstruct high-framerate RF images with bidirectional oscillations in the pulse-echo field. Such RF images are then processed by a 2-D phase-based displacement estimator to produce 2-D vector flow maps at thousands of frames per second. First, the capability of generating TOs after PW transmissions was thoroughly investigated by varying the lateral wavelength, the burst length, and the transmission frequency. Over the entire region of interest, the generated lateral wavelengths, compared with the designed ones, presented bias and standard deviation of -3.3 ± 5.7% and 10.6 ± 7.4% in simulations and experiments, respectively. The performance of the ultrafast vector flow mapping method was also assessed by evaluating the differences between the estimated velocities and the expected ones. Both simulations and experiments show overall biases lower than 20% when varying the beam-to-flow angle, the peak velocity, and the depth of interest. In vivo applications of the method on the common carotid and the brachial arteries are also presented.

  19. Temporal Non-locality

    NASA Astrophysics Data System (ADS)

    Filk, Thomas

    2013-04-01

    In this article I investigate several possibilities to define the concept of "temporal non-locality" within the standard framework of quantum theory. In particular, I analyze the notions of "temporally non-local states", "temporally non-local events" and "temporally non-local observables". The idea of temporally non-local events is already inherent in the standard formalism of quantum mechanics, and Basil Hiley recently defined an operator in order to measure the degree of such a temporal non-locality. The concept of temporally non-local states enters as soon as "clock-representing states" are introduced in the context of special and general relativity. It is discussed in which way temporally non-local measurements may find an interesting application for experiments which test temporal versions of Bell inequalities.

  20. Million Atom Pseudopotential Manybody Theory of Electronic Structure and Spectroscopy of Semiconductor Quantum Dots

    NASA Astrophysics Data System (ADS)

    Zunger, Alex

    2003-03-01

    Semiconductor Quantum Dots that are of sufficient structural quality (good crystallinity, surface passivation, size uniformity) to produce ultra sharp spectroscopic lines worthy of a detailed theoretical effort tend to be rather BIG, containing thousands to million atoms. Yet, in this size regime, the only theoretical methods available are effective-mass based, particle-in-a-box approaches, that neglect multi-band and inter-valley coupling, leading to significant qualitative errors.(A. Zunger,Phys. Stat. Sol. (a) 190), 467 (2002). While LDA-based methods are capable of solving the Single-Particle problem even for ˜1,000 atom dots, the all important many-body problem can be currently addressed only for considerably smaller dots. I will present here a computational alternative which addresses both the single-particle and the Manybody parts of the problem for 10^3 to 10^6 atom dots .The method is applicable both to ``free Standing" (e.g. colloidal) dots of CdSe, InP, InAs and Si, as well as to the strained, ``self-assembled" epitaxial dots of, e.g., InGaAs/GaAs. It is based on a ``Linear Combination of Bulk Bands" (LCBB) approach that expands the dot states in terms of plane wave based (pseudopotential) Bloch states throughout the Brillouin zone. The manybody part is treated via Configuration Interaction. I will illustrate how this method addresses some of the recent striking experimental observations on semiconductor quantum dots:(i) Scaling laws for band gaps and exchange interactions (ii) Rapid Auger transitions in colloidal dots (iii) Coulomb Blocade and Spin Blockade in colloidal dots (iv) Charged Excitons (e.g. Trions) in Self-assembled dots, and (v) excitonic Fine-Structure in self assembled dots.

  1. Radiation of de-excited electrons at large times in a strong electromagnetic plane wave

    SciTech Connect

    Kazinski, P.O.

    2013-12-15

    The late time asymptotics of the physical solutions to the Lorentz–Dirac equation in the electromagnetic external fields of simple configurations–the constant homogeneous field, the linearly polarized plane wave (in particular, the constant uniform crossed field), and the circularly polarized plane wave–are found. The solutions to the Landau–Lifshitz equation for the external electromagnetic fields admitting a two-parametric symmetry group, which include as a particular case the above mentioned field configurations, are obtained. Some general properties of the total radiation power of a charged particle are established. In particular, for a circularly polarized wave and constant uniform crossed fields, the total radiation power in the asymptotic regime is independent of the charge and the external field strength, when expressed in terms of the proper-time, and equals a half the rest energy of a charged particle divided by its proper-time. The spectral densities of the radiation power formed on the late time asymptotics are derived for a charged particle moving in the external electromagnetic fields of the simple configurations pointed above. This provides a simple method to verify experimentally that the charged particle has reached the asymptotic regime. -- Highlights: •Late time asymptotics of the solutions to the Lorentz–Dirac equation are studied. •General properties of the total radiation power of electrons are established. •The total radiation power equals a half the rest energy divided by the proper-time. •Spectral densities of radiation formed on the late time asymptotics are derived. •Possible experimental verification of the results is proposed.

  2. Robust angle-independent blood velocity estimation based on dual-angle plane wave imaging.

    PubMed

    Fadnes, Solveig; Ekroll, Ingvild Kinn; Nyrnes, Siri Ann; Torp, Hans; Lovstakken, Lasse

    2015-10-01

    Two-dimensional blood velocity estimation has shown potential to solve the angle-dependency of conventional ultrasound flow imaging. Clutter filtering, however, remains a major challenge for large beam-to-flow angles, leading to signal drop-outs and corrupted velocity estimates. This work presents and evaluates a compounding speckle tracking (ST) algorithm to obtain robust angle-independent 2-D blood velocity estimates for all beam-to-flow angles. A dual-angle plane wave imaging setup with full parallel receive beamforming is utilized to achieve high-frame-rate speckle tracking estimates from two scan angles, which may be compounded to obtain velocity estimates of increased robustness. The acquisition also allows direct comparison with vector Doppler (VD) imaging. Absolute velocity bias and root-mean-square (RMS) error of the compounding ST estimations were investigated using simulations of a rotating flow phantom with low velocities ranging from 0 to 20 cm/s. In a challenging region where the estimates were influenced by clutter filtering, the bias and RMS error for the compounding ST estimates were 11% and 2 cm/s, a significant reduction compared with conventional single-angle ST (22% and 4 cm/s) and VD (36% and 6 cm/s). The method was also tested in vivo for vascular and neonatal cardiac imaging. In a carotid artery bifurcation, the obtained blood velocity estimates showed that the compounded ST method was less influenced by clutter filtering than conventional ST and VD methods. In the cardiac case, it was observed that ST velocity estimation is more affected by low signal-to-noise (SNR) than VD. However, with sufficient SNR the in vivo results indicated that a more robust angle-independent blood velocity estimator is obtained using compounded speckle tracking compared with conventional ST and VD methods. PMID:26470038

  3. Robust angle-independent blood velocity estimation based on dual-angle plane wave imaging.

    PubMed

    Fadnes, Solveig; Ekroll, Ingvild Kinn; Nyrnes, Siri Ann; Torp, Hans; Lovstakken, Lasse

    2015-10-01

    Two-dimensional blood velocity estimation has shown potential to solve the angle-dependency of conventional ultrasound flow imaging. Clutter filtering, however, remains a major challenge for large beam-to-flow angles, leading to signal drop-outs and corrupted velocity estimates. This work presents and evaluates a compounding speckle tracking (ST) algorithm to obtain robust angle-independent 2-D blood velocity estimates for all beam-to-flow angles. A dual-angle plane wave imaging setup with full parallel receive beamforming is utilized to achieve high-frame-rate speckle tracking estimates from two scan angles, which may be compounded to obtain velocity estimates of increased robustness. The acquisition also allows direct comparison with vector Doppler (VD) imaging. Absolute velocity bias and root-mean-square (RMS) error of the compounding ST estimations were investigated using simulations of a rotating flow phantom with low velocities ranging from 0 to 20 cm/s. In a challenging region where the estimates were influenced by clutter filtering, the bias and RMS error for the compounding ST estimates were 11% and 2 cm/s, a significant reduction compared with conventional single-angle ST (22% and 4 cm/s) and VD (36% and 6 cm/s). The method was also tested in vivo for vascular and neonatal cardiac imaging. In a carotid artery bifurcation, the obtained blood velocity estimates showed that the compounded ST method was less influenced by clutter filtering than conventional ST and VD methods. In the cardiac case, it was observed that ST velocity estimation is more affected by low signal-to-noise (SNR) than VD. However, with sufficient SNR the in vivo results indicated that a more robust angle-independent blood velocity estimator is obtained using compounded speckle tracking compared with conventional ST and VD methods.

  4. Cylindrical and spherical space equivalents to the plane wave expansion technique of Maxwell's wave equations

    NASA Astrophysics Data System (ADS)

    Gauthier, Robert C.; Alzahrani, Mohammed A.; Jafari, Seyed Hamed

    2015-02-01

    The plane wave expansion (PWM) technique applied to Maxwell's wave equations provides researchers with a supply of information regarding the optical properties of dielectric structures. The technique is well suited for structures that display a linear periodicity. When the focus is directed towards optical resonators and structures that lack linear periodicity the eigen-process can easily exceed computational resources and time constraints. In the case of dielectric structures which display cylindrical or spherical symmetry, a coordinate system specific set of basis functions have been employed to cast Maxwell's wave equations into an eigen-matrix formulation from which the resonator states associated with the dielectric profile can be obtained. As for PWM, the inverse of the dielectric and field components are expanded in the basis functions (Fourier-Fourier-Bessel, FFB, in cylindrical and Fourier- Bessel-Legendre, BLF, in spherical) and orthogonality is employed to form the matrix expressions. The theoretical development details will be presented indicating how certain mathematical complications in the process have been overcome and how the eigen-matrix can be tuned to a specific mode type. The similarities and differences in PWM, FFB and BLF are presented. In the case of structures possessing axial cylindrical symmetry, the inclusion of the z axis component of propagation constant makes the technique applicable to photonic crystal fibers and other waveguide structures. Computational results will be presented for a number of different dielectric geometries including Bragg ring resonators, cylindrical space slot channel waveguides and bottle resonators. Steps to further enhance the computation process will be reported.

  5. Effect of deviation from plane wave conditions on the Doppler spectrum from an ultrasonic blood flow detector.

    PubMed

    Ata, O W; Fish, P J

    1991-09-01

    Deviation from plane wave conditions within the ultrasound beam of a Doppler blood flow detector leads to a non-linear relationship between the phase angle of the back-scattered signal and the scatterer position. This in turn leads to frequency modulation of the Doppler signal and an increase in the Doppler spectrum width. The relationship between the ultrasound beam and the observed signal spectrum has been investigated by employing a computer-based model of the ultrasound field which enabled the calculation of: 1, pressure (amplitude and phase angle) field distributions from plane disc and focused transducers with unapodized and apodized aperture field distributions; 2, the Doppler signal from a scatterer moving through the field; and 3, the spectrum of this signal. The increase in spectral width resulting from deviations from plane wave conditions was calculated by comparing this spectrum with that of the signal from which frequency modulation had been removed.

  6. Plane wave propagation in a rotating anisotropic medium with voids under the action of a uniform magnetic field

    NASA Astrophysics Data System (ADS)

    Maity, Narottam; Barik, S. P.; Chaudhuri, P. K.

    2016-09-01

    In this paper, plane wave propagation in a rotating anisotropic material of general nature under the action of a magnetic field of constant magnitude has been investigated. The material is supposed to be porous in nature and contains voids. Following the concept of [Cowin S. C. and Nunziato, J. W. [1983] “Linear elastic materials with voids,” J. Elasticity 13, 125-147.] the governing equations of motion have been written in tensor notation taking account of rotation, magnetic field effect and presence of voids in the medium and the possibility of plane wave propagation has been examined. A number of particular cases have been derived from our general results to match with previously obtained results in this area. Effects of various parameters on the velocity of wave propagation have been presented graphically.

  7. Scattering of an electromagnetic plane wave by a homogeneous sphere made of an orthorhombic dielectric-magnetic material.

    PubMed

    Ulfat Jafri, A D; Lakhtakia, Akhlesh

    2014-01-01

    An exact transition matrix was formulated for electromagnetic scattering by an orthorhombic dielectric-magnetic sphere whose permeability dyadic is a scalar multiple of its permittivity dyadic. Calculations were made for plane waves incident on the sphere. As the size parameter increases, the role of anisotropy evolves; multiple lobes appear in the plots of the differential scattering efficiency in any scattering plane; the total scattering, extinction, and forward-scattering efficiencies exhibit a prominent maximum each; and the absorption efficiency generally increases with weak undulations. Certain orientations of the sphere with respect to the directions of propagation and the electric field of the incident plane wave make it highly susceptible to detection in a monostatic configuration, whereas other orientations make it much less vulnerable to detection. Impedance match to the ambient free space decreases backscattering efficiency significantly, although anisotropy prevents null backscattering. PMID:24561944

  8. Transformations of spherical beam shape coefficients in generalized Lorenz-Mie theories through rotations of coordinate systems. IV. Plane waves

    NASA Astrophysics Data System (ADS)

    Gouesbet, G.; Wang, J. J.; Han, Y. P.; G. Grehan

    2010-09-01

    This paper is the fourth of a series devoted to the transformation of beam shape coefficients through rotations of coordinate systems. These coefficients are required to express electromagnetic fields of laser beams in expanded forms, for instance for use in some generalized Lorenz-Mie theories. The main result of Part I has been the theorem of transformation of beam shape coefficients under rotations. Part II dealt with the special case of on-axis axisymmetric beams. Part III dealt with other special cases, namely when the Euler angles specifying the rotation are given some special values. The present Part IV studies another special case, namely the one of plane waves viewed as special on-axis axisymmetric beams, and can therefore be viewed as a special case of Part II. Unexpectedly, it is found that, in general, although plane waves are fairly trivial, their expansions require using non trivial beam shape coefficients, exactly as required when dealing with arbitrary shaped beams.

  9. Full-wave model and numerical study of electromagnetic plane wave scattering by multilayered, fiber-based periodic composites

    NASA Astrophysics Data System (ADS)

    Li, C. Y.; Lesselier, D.; Zhong, Y.

    2015-07-01

    The present work aims at building up a full-wave computational model of electromagnetic nondestructive testing of composite materials produced by stacking up dielectric slabs one over the other. In each such dielectric slab, a periodic array of infinite cylindrical fibers is embedded. Electromagnetic scattering of such a multilayered, fiber-based periodic composite is investigated here for an obliquely incident plane wave, the plane of incidence of which differs from the plane orthogonal to the fibers' axes. Full-wave field representations are given first by multipole and plane wave expansions. Mode matching at boundaries between layers then yields the propagating matrices, which are applied to connect reflection and transmission coefficients of the longitudinal field components. Power reflection and transmission coefficients are obtained from time-averaged Poynting vectors. Numerical experiments with comparisons with known results illustrate the accuracy of the model proposed.

  10. Scattering of an electromagnetic plane wave by a homogeneous sphere made of an orthorhombic dielectric-magnetic material.

    PubMed

    Ulfat Jafri, A D; Lakhtakia, Akhlesh

    2014-01-01

    An exact transition matrix was formulated for electromagnetic scattering by an orthorhombic dielectric-magnetic sphere whose permeability dyadic is a scalar multiple of its permittivity dyadic. Calculations were made for plane waves incident on the sphere. As the size parameter increases, the role of anisotropy evolves; multiple lobes appear in the plots of the differential scattering efficiency in any scattering plane; the total scattering, extinction, and forward-scattering efficiencies exhibit a prominent maximum each; and the absorption efficiency generally increases with weak undulations. Certain orientations of the sphere with respect to the directions of propagation and the electric field of the incident plane wave make it highly susceptible to detection in a monostatic configuration, whereas other orientations make it much less vulnerable to detection. Impedance match to the ambient free space decreases backscattering efficiency significantly, although anisotropy prevents null backscattering.

  11. Rigorous formulation for electromagnetic plane-wave scattering from a general-shaped groove in a perfectly conducting plane: comment.

    PubMed

    Skigin, Diana C; Depine, Ricardo A

    2008-05-01

    We show that the problem of scattering of an obliquely incident plane wave by a general-shaped groove engraved on a perfectly conducting plane, which was recently studied by Basha et al. [J. Opt. Soc. Am. A24, 1647 (2007)], was solved 11 years ago using the same formulation. This method was further extended to deal with a finite number of grooves and also with complex apertures including several nonlossy and lossy dielectrics, as well as real metals.

  12. Process e/sup -/. -->. e/sup -/(. nu. nu-bar) in the field of a circularly polarized plane wave

    SciTech Connect

    Skobelev, V.V.

    1987-12-01

    The e/sup -/..-->..e/sup -/(..nu..nu-bar) process in the field of a circularly polarized plane wave is studied in the framework of the Glashow-Weinberg-Salam model. General expressions for the probability of creation of neutrino pairs are obtained, and the case of a low-intensity wave is studied in detail. The effects of asymmetry of emission of electron and muon neutrinos are estimated, and comparison with previous results is performed.

  13. Complex coordinate implementation in the curvilinear coordinate method: application to plane-wave diffraction by nonperiodic rough surfaces.

    PubMed

    Edee, Kofi; Granet, Gérard; Plumey, Jean-Píerre

    2007-04-01

    We investigate the electromagnetic modeling of plane-wave diffraction by nonperiodic surfaces by using the curvilinear coordinate method (CCM). This method is often used with a Fourier basis expansion, which results in the periodization of both the geometry and the electromagnetic field. We write the CCM in a complex coordinate system in order to introduce the perfectly matched layer concept in a simple and efficient way. The results, presented for a perfectly conducting surface, show the efficiency of the model.

  14. Plane-wave spectrum approach for the AC thermal analysis of vertical thermal resistance on sample surface

    NASA Astrophysics Data System (ADS)

    Grossel, Philippe; Depasse, Françoise; Gomès, Séverine

    1999-08-01

    The perturbation caused by a vertical thermal resistance to the alternating current temperature field in a homogeneous sample is analysed by using a plane-wave spectrum for which the reference plane is perpendicular to the crack. This unusual Fourier analysis gives rapid access to the temperature field in the frequency domain at any place in the sample. This can thus furnish the source term for a complete thermoelastic local response and complete the available surface temperature data.

  15. An algorithm for the calculation of the partial wave expansion of the Coulomb-distorted plane wave

    NASA Astrophysics Data System (ADS)

    Hornyak, I.; Kruppa, A. T.

    2015-12-01

    The partial wave expansion of the Coulomb-distorted plane wave is determined by the help of the complex generalized hypergeometric function 2F2(a , a ; a + l + 1 , a - l ; z) . An algorithm for the calculation of 2F2(a , a ; a + l + 1 , a - l ; z) is created and it is implemented as a FORTRAN-90 code. The code is fast and its accuracy is 14 significant decimal digits.

  16. Modelling ultrasonic array signals in multilayer anisotropic materials using the angular spectrum decomposition of plane wave responses

    NASA Astrophysics Data System (ADS)

    Humeida, Yousif; Pinfield, Valerie J.; Challis, Richard E.

    2013-08-01

    Ultrasonic arrays have seen increasing use for the characterisation of composite materials. In this paper, ultrasonic wave propagation in multilayer anisotropic materials has been modelled using plane wave and angular spectrum decomposition techniques. Different matrix techniques, such as the stiffness matrix method and the transfer matrix method, are used to calculate the reflection and transmission coefficients of ultrasonic plane waves in the considered media. Then, an angular decomposition technique is used to derive the bounded beams from finite-width ultrasonic array elements from the plane wave responses calculated earlier. This model is considered to be an analytical exact solution for the problem; hence the diffraction of waves in such composite materials can be calculated for different incident angles for a very wide range of frequencies. This model is validated against experimental measurements using the Full-Matrix Capture (FMC) of array data in both a homogeneous isotropic material, i.e. aluminium, and an inhomogeneous multilayer anisotropic material, i.e. a carbon fibre reinforced composite.

  17. Relativistic small-core pseudopotentials for actinium, thorium, and protactinium.

    PubMed

    Weigand, Anna; Cao, Xiaoyan; Hangele, Tim; Dolg, Michael

    2014-04-01

    Small-core pseudopotentials for actinium, thorium, and protactinium have been energy-adjusted to multiconfiguration Dirac-Hartree-Fock reference data based on the Dirac-Coulomb-Breit Hamiltonian and the Fermi nucleus model. Corresponding optimized valence basis sets of polarized valence quadruple-ζ quality are presented. Atomic test calculations for the first four ionization potentials show satisfactory results at both the Hartree-Fock and the multireference averaged coupled-pair functional level. Highly correlated Fock-space coupled cluster calculations demonstrate that the new pseudopotentials yield ionization potentials, which are in excellent agreement with corresponding all-electron results and experimental data. The pseudopotentials and basis sets supplement a similar set previously published for uranium.

  18. Relativistic small-core pseudopotentials for actinium, thorium, and protactinium.

    PubMed

    Weigand, Anna; Cao, Xiaoyan; Hangele, Tim; Dolg, Michael

    2014-04-01

    Small-core pseudopotentials for actinium, thorium, and protactinium have been energy-adjusted to multiconfiguration Dirac-Hartree-Fock reference data based on the Dirac-Coulomb-Breit Hamiltonian and the Fermi nucleus model. Corresponding optimized valence basis sets of polarized valence quadruple-ζ quality are presented. Atomic test calculations for the first four ionization potentials show satisfactory results at both the Hartree-Fock and the multireference averaged coupled-pair functional level. Highly correlated Fock-space coupled cluster calculations demonstrate that the new pseudopotentials yield ionization potentials, which are in excellent agreement with corresponding all-electron results and experimental data. The pseudopotentials and basis sets supplement a similar set previously published for uranium. PMID:24628327

  19. Hand-held forward-looking focused array mine detection with plane wave excitation

    NASA Astrophysics Data System (ADS)

    Rappaport, Carey M.; Azevedo, Stephen G.; Rosenbury, Tom; Gough, Jamie; Jin, Dongping

    2000-08-01

    A novel handheld time-domain array GPR antipersonnel mine detection system prototype has been developed. Using an offset paraboloidal reflector antenna to collimate rays form an ultra-wideband feed, the transmitted microwave impulse is concentrated forward, in front of the antenna structure. The resulting wave is a non-uniform plane wave over the portion of ground be investigated, and is incident at 45 degrees to normal. As such, much of the ground reflect wave is directed further forward, away from the operator, the reflector, and the receiving antennas, thereby reducing clutter. However, the wave transmitted into the ground, which interacts with the target, tends to have significant backscatter returning toward the receiving antennas. These receiving antennas are configured in a 2 by 2 array to provide spatial focusing in both along and cross-track directions. This is accomplished by measuring and comparing the backscattered signal at each receiver in the narrow time window between the times when the ground reflected wave passes the receiver and before this wave re-reflects from the reflector components. 2D FDTD simulation of this parabolic reflector transmitter indicates that it generates a beam with a non-uniform planar wavefront, which scatters form rough ground primarily in the forward direction. The wave transmitted into the ground is also planar, propagating at the angle of refraction, and scattering fairly isotropically from a small penetrable target. This system has been built and tested at LLNL, using a very narrow pulse shape. LLNL's Micro-Impulse Radar (MIR) and custom-built wideband antenna elements operate in the 1.5 to 5 GHz range. One particular advantage of using the MIR module is its low cost: an important feature for mine detectors used in developing countries. Preliminary measured data indicates that the surface clutter is indeed reduced relative to the target signal, and that small non-metallic anti-personnel mines can be reliably detected at

  20. The Plane Wave Spectrum in Acousto-Optic Imaging of Ultrasonic Fields.

    NASA Astrophysics Data System (ADS)

    Mehrl, David Joseph

    This thesis takes an in-depth look at two major areas of acousto-optics: Bragg diffraction imaging and Schlieren imaging. Both of these methods relate to the imaging of ultrasonic sound fields. The latter method is particularly relevant as it forms the basis for many practical signal processing schemes. A review of the angular plane wave spectrum concept is followed by an outline of a three-dimensional acousto -optic interaction formalism. This formalism forms the basis for the wave-theory analyses of Bragg diffraction and Schlieren imaging which are undertaken in later chapters. A ray tracing method, applicable to acousto-optic scattering, is also developed and justified on the basis of eikonal theory. Bragg diffraction imaging is analyzed by means of both ray tracing and wave theory methods, and the results are shown to be in mutual agreement. Also discussed are the development and results of a computer program which generates three-dimensional ray tracings that depict various Bragg diffraction imaging configurations. Experimental results are presented that support our theoretical findings. Schlieren imaging is analyzed in chapter 4. The classical Raman-Nath model (and its limitations) is first discussed. We then proceed to analyze Schlieren imaging by means of wave theory. We find that the Schlieren image of a monophonic sound field possesses an extremely large depth of focus (i.e. it is almost diffraction free). We proceed to show that the Raman-Nath interpretation can be extended to high frequency (Bragg) regimes, provided certain constraints are met. Finally, we examine wideband Schlieren imaging using optical heterodyning, which is of great practical importance in signal processing schemes. Several key results are obtained. We first present an illustrative example of a Schlieren signal processing scheme employing optical heterodyning. Although this scheme is not new per se, we present experimental results of a working experiment in which we correlate a pulse

  1. Correlated electron pseudopotentials for 3d-transition metals

    SciTech Connect

    Trail, J. R. Needs, R. J.

    2015-02-14

    A recently published correlated electron pseudopotentials (CEPPs) method has been adapted for application to the 3d-transition metals, and to include relativistic effects. New CEPPs are reported for the atoms Sc − Fe, constructed from atomic quantum chemical calculations that include an accurate description of correlated electrons. Dissociation energies, molecular geometries, and zero-point vibrational energies of small molecules are compared with all electron results, with all quantities evaluated using coupled cluster singles doubles and triples calculations. The CEPPs give better results in the correlated-electron calculations than Hartree-Fock-based pseudopotentials available in the literature.

  2. Nonlocal magnetorotational instability

    SciTech Connect

    Mikhailovskii, A. B.; Erokhin, N. N.; Lominadze, J. G.; Galvao, R. M. O.; Churikov, A. P.; Kharshiladze, O. A.; Amador, C. H. S.

    2008-05-15

    An analytical theory of the nonlocal magnetorotational instability (MRI) is developed for the simplest astrophysical plasma model. It is assumed that the rotation frequency profile has a steplike character, so that there are two regions in which it has constant different values, separated by a narrow transition layer. The surface wave approach is employed to investigate the MRI in this configuration. It is shown that the main regularities of the nonlocal MRI are similar to those of the local instability and that driving the nonaxisymmetric MRI is less effective than the axisymmetric one, also for the case of the nonlocal instability. The existence of nonlocal instabilities in nonmagnetized plasma is predicted.

  3. Automated generation of highly accurate, efficient and transferable pseudopotentials

    NASA Astrophysics Data System (ADS)

    Hansel, R. A.; Brock, C. N.; Paikoff, B. C.; Tackett, A. R.; Walker, D. G.

    2015-11-01

    A multi-objective genetic algorithm (MOGA) was used to automate a search for optimized pseudopotential parameters. Pseudopotentials were generated using the atomPAW program and density functional theory (DFT) simulations were conducted using the pwPAW program. The optimized parameters were the cutoff radius and projector energies for the s and p orbitals. The two objectives were low pseudopotential error and low computational work requirements. The error was determined from (1) the root mean square difference between the all-electron and pseudized-electron log derivative, (2) the calculated lattice constant versus reference data of Holzwarth et al., and (3) the calculated bulk modulus versus reference potentials. The computational work was defined as the number of flops required to perform the DFT simulation. Pseudopotential transferability was encouraged by optimizing each element in different lattices: (1) nitrogen in GaN, AlN, and YN, (2) oxygen in NO, ZnO, and SiO4, and (3) fluorine in LiF, NaF, and KF. The optimal solutions were equivalent in error and required significantly less computational work than the reference data. This proof-of-concept study demonstrates that the combination of MOGA and ab-initio simulations is a powerful tool that can generate a set of transferable potentials with a trade-off between accuracy (error) and computational efficiency (work).

  4. Generalized pseudopotential approach for electron-atom scattering.

    NASA Technical Reports Server (NTRS)

    Zarlingo, D. G.; Ishihara, T.; Poe, R. T.

    1972-01-01

    A generalized many-electron pseudopotential approach is presented for electron-neutral-atom scattering problems. A calculation based on this formulation is carried out for the singlet s-wave and p-wave electron-hydrogen phase shifts with excellent results. We compare the method with other approaches as well as discuss its applications for inelastic and rearrangement collision problems.

  5. Band structure of W and Mo by empirical pseudopotential method

    NASA Technical Reports Server (NTRS)

    Sridhar, C. G.; Whiting, E. E.

    1977-01-01

    The empirical pseudopotential method (EPM) is used to calculate the band structure of tungsten and molybdenum. Agreement between the calculated reflectivity, density of states, density of states at the Fermi surface and location of the Fermi surface from this study and experimental measurements and previous calculations is good. Also the charge distribution shows the proper topological distribution of charge for a bcc crystal.

  6. The influence of the plane wave spectrum of A source on measurements of the transmission coefficient of a panel

    NASA Astrophysics Data System (ADS)

    Humphrey, V. F.

    1986-07-01

    The transmission coefficient of a panel immersed in a fluid, as measured by a circular projector, is considered. An integral expression for the measured coefficient is derived, with account taken of the non-planar nature of the wavefield and the finite size of the receiver. Numerical integration of this expression shows that the measured transmission coefficient can deviate significantly from the value predicted for a plane wave. The theoretical predictions are compared with experimental measurements of the insertion loss at normal incidence of two Perspex (polymethylmethacrylate) panels 1·4 mm and 3·1 mm thick. These measurements, which were recorded as a function of frequency and transducer separation, were concentrated in the frequency bands where the panels were approximately half a compressional wavelength thick (i.e., for frequency-panel thickness products of the order of 1·35×10 3 Hzm). In this region the measured insertion loss varied rapidly with frequency and was observed to deviate significantly from the slowly varying loss predicted for plane waves. Such deviations were observed when a small hydrophone was used as the receiver and also when another transducer of the same radius as the projector was used as the receiver. For measurements made outside the "nearfield" of the transducer combination the results were in very good agreement with the predictions of the theoretical expression. At closer ranges the poorer quantitative agreement was attributed to the transducers not behaving as ideal pistons. The results and theoretical calculations show that the plane wave spectrum of a source can have a significant effect on the measured transmission coefficient of a panel, particularly at frequencies where the transmission coefficient changes rapidly with angle of incidence.

  7. Extending the size-parameter range for plane-wave light scattering from infinite homogeneous circular cylinders

    SciTech Connect

    Hau-Riege, S

    2005-04-12

    We have developed an algorithm that extends the possible size-parameter range for the calculation of plane-wave light scattering from infinite homogeneous circular cylinders using a Mie-type analysis. Our algorithm is based on the calculation of the ratios of Bessel functions instead of calculating the Bessel functions or their logarithmic derivatives directly. We have found that this algorithm agrees with existing methods (when those methods converge). We have also found that our algorithm converges in cases of very large size parameters, in which case other algorithms often do not.

  8. Generalized plane-wave expansion of cylindrical functions in lossy media convergent in the whole complex plane

    NASA Astrophysics Data System (ADS)

    Frezza, F.; Schettini, G.; Tedeschi, N.

    2011-08-01

    Electromagnetic scattering by buried objects may involve a plane-wave expansion of the related fields, which depends on the objects' geometry. Furthermore, involved media in realistic cases are lossy, which requires the analytic continuation of formulae known for the lossless cases, due to the complex nature of the wave vectors. This problem has been covered in a previous paper, but the expression found still does not converge in some areas of space. In this paper, a new, convergent, expression of the spectrum of cylindrical functions in lossy media is analytically computed and its convergence limits are discussed.

  9. Diffraction of a plane wave by an infinitely long circular cylinder or a sphere: solution from Mie theory.

    PubMed

    Shen, Jianqi; Jia, Xiaowei

    2013-08-10

    Diffraction of an infinitely long circular cylinder normally illuminated by a plane wave is discussed from the classical Mie theory. A rigorous expression of the diffracted light is obtained, which is simply characterized by a factor (θ/2)/sin(θ/2) and the sinc function sin(αθ)/(αθ). Numerical calculation shows an apparent difference between our results and those from scalar wave diffraction theory, especially in large diffraction angles. The factor (θ/2)/sin(θ/2) is introduced into the diffracted light by a sphere, which leads to an alternative approximation of the diffracted light.

  10. Fast calculation method for optical diffraction on tilted planes by use of the angular spectrum of plane waves

    NASA Astrophysics Data System (ADS)

    Matsushima, Kyoji; Schimmel, Hagen; Wyrowski, Frank

    2003-09-01

    A novel method for simulating field propagation is presented. The method, based on the angular spectrum of plane waves and coordinate rotation in the Fourier domain, removes geometric limitations posed by conventional propagation calculation and enables us to calculate complex amplitudes of diffracted waves on a plane not parallel to the aperture. This method can be implemented by using the fast Fourier transformation twice and a spectrum interpolation. It features computation time that is comparable with that of standard calculation methods for diffraction or propagation between parallel planes. To demonstrate the method, numerical results as well as a general formulation are reported for a single-axis rotation.

  11. On the description of electromagnetic arbitrary shaped beams: The relationship between beam shape coefficients and plane wave spectra

    NASA Astrophysics Data System (ADS)

    Gouesbet, Gérard; Lock, James A.

    2015-09-01

    A strong effort has been devoted during the last three decades, and more, to the study of electromagnetic scattering of arbitrary shaped beams by particles. For this topic, the most important issue concerns the description of the illuminating beam as an expansion over a basis of functions. There are essentially two kinds of expansions that have been used: (i) a discrete expansion involving beam shape coefficients and (ii) a continuous expansion in terms of plane wave spectra. In this paper, we provide a formal relationship between these two kinds of expansions.

  12. Plane-wave and common-translation-factor treatments of He sup 2+ +H collisions at high velocities

    SciTech Connect

    Errea, L.F. ); Harel, C.; Jouin, H. ); Maidagan, J.M.; Mendez, L. ); Pons, B. ); Riera, A. )

    1992-11-01

    We complement previous work that showed that the molecular approach, modified with plane-wave translation factors, is able to reproduce the fall of charge-exchange cross sections in He{sup 2+}+H collisions, by presenting the molecular data, and studying the corresponding mechanism. We test the accuracy of simplifications of the method that have been employed in the literature, and that lead to very simple calculations. We show that the common-translation-factor method is also successful at high nuclear velocities, provided that sufficiently excited states are included in the basis; moreover, it yields a simple picture of the mechanism and a description of ionization processes at high velocities.

  13. Correction of the near threshold behavior of electron collisional excitation cross-sections in the plane-wave Born approximation

    DOE PAGES

    Kilcrease, D. P.; Brookes, S.

    2013-08-19

    The modeling of NLTE plasmas requires the solution of population rate equations to determine the populations of the various atomic levels relevant to a particular problem. The equations require many cross sections for excitation, de-excitation, ionization and recombination. Additionally, a simple and computational fast way to calculate electron collisional excitation cross-sections for ions is by using the plane-wave Born approximation. This is essentially a high-energy approximation and the cross section suffers from the unphysical problem of going to zero near threshold. Various remedies for this problem have been employed with varying degrees of success. We present a correction procedure formore » the Born cross-sections that employs the Elwert–Sommerfeld factor to correct for the use of plane waves instead of Coulomb waves in an attempt to produce a cross-section similar to that from using the more time consuming Coulomb Born approximation. We compare this new approximation with other, often employed correction procedures. Furthermore, we also look at some further modifications to our Born Elwert procedure and its combination with Y.K. Kim's correction of the Coulomb Born approximation for singly charged ions that more accurately approximate convergent close coupling calculations.« less

  14. Comparative analysis on viewing angle change in Fresnel and Fourier holographic images reconstructed by a tilted plane wave.

    PubMed

    Chae, Byung Gyu

    2014-05-20

    We carry out a comparative analysis on a viewing angle change in Fresnel and Fourier holographic images reconstructed by a tilted plane wave. A tilted plane wave illuminating an on-axis hologram generates a diffractive wave carrying the holographic image in a paraxial region of a new diffraction axis. The reconstructed image in the Fresnel hologram is deformed along the new viewing direction, which is well described as Affine transformation. In the Fourier holographic image, the replica of the image is formed without its deformation when the hologram is placed in the front focal plane of the lens, whereas in the case of a hologram that is located at a distance different from a focal length, image deformation arises. This property is investigated through numerical simulation based on a wide-angle diffraction phenomenon. We also perform a similar interpretation for high-order diffraction images appearing in the sampled Fourier hologram and discuss a method for enlarging the viewing angle of the holographic image.

  15. Electron transport in graphene/graphene side-contact junction by plane-wave multiple-scattering method

    DOE PAGES

    Li, Xiang-Guo; Chu, Iek-Heng; Zhang, X. -G.; Cheng, Hai-Ping

    2015-05-28

    Electron transport in graphene is along the sheet but junction devices are often made by stacking different sheets together in a “side-contact” geometry which causes the current to flow perpendicular to the sheets within the device. Such geometry presents a challenge to first-principles transport methods. We solve this problem by implementing a plane-wave-based multiple-scattering theory for electron transport. In this study, this implementation improves the computational efficiency over the existing plane-wave transport code, scales better for parallelization over large number of nodes, and does not require the current direction to be along a lattice axis. As a first application, wemore » calculate the tunneling current through a side-contact graphene junction formed by two separate graphene sheets with the edges overlapping each other. We find that transport properties of this junction depend strongly on the AA or AB stacking within the overlapping region as well as the vacuum gap between two graphene sheets. Finally, such transport behaviors are explained in terms of carbon orbital orientation, hybridization, and delocalization as the geometry is varied.« less

  16. Accurate all-electron G0W0 quasiparticle energies employing the full-potential augmented plane-wave method

    NASA Astrophysics Data System (ADS)

    Nabok, Dmitrii; Gulans, Andris; Draxl, Claudia

    2016-07-01

    The G W approach of many-body perturbation theory has become a common tool for calculating the electronic structure of materials. However, with increasing number of published results, discrepancies between the values obtained by different methods and codes become more and more apparent. For a test set of small- and wide-gap semiconductors, we demonstrate how to reach the numerically best electronic structure within the framework of the full-potential linearized augmented plane-wave (FLAPW) method. We first evaluate the impact of local orbitals in the Kohn-Sham eigenvalue spectrum of the underlying starting point. The role of the basis-set quality is then further analyzed when calculating the G0W0 quasiparticle energies. Our results, computed with the exciting code, are compared to those obtained using the projector-augmented plane-wave formalism, finding overall good agreement between both methods. We also provide data produced with a typical FLAPW basis set as a benchmark for other G0W0 implementations.

  17. Internal electric energy in a spherical particle illuminated with a plane wave or off-axis Gaussian beam.

    PubMed

    Khaled, E E; Hill, S C; Barber, P W

    1994-01-20

    The electric energy in a lossless or lossy spherical particle that is illuminated with a plane wave or a Gaussian beam is investigated. The analysis uses a combination of the plane-wave spectrum technique and the T-matrix method. Expressions for the electric energy in any mode as well as the total electric energy inside the particle are given. The amount of energy coupling into the particle for different beam illuminations is also investigated. The high-Q (low-order) resonant modes can dominate the electric energy inside a spherical particle many linewidths away from the resonance location, particularly if the beam is focused at the droplet edge or outside the droplet. If the sphere is lossy, low-order modes can still dominate the electric energy if the beam is focused far enough outside the sphere. As the absorption coefficient of the particle increases, the energy in a high-Q mode decreases much faster at the resonance frequency than it does at near or off-resonance frequencies. The effects of the absorption on the dominance of the internal fields by a high-Q mode decreases as the beam is shifted farther away from the particle. As the beam is shifted farther away from the particle the fraction of the incident energy coupled into the sphere at resonance first increases and then decreases. Although the coupled energy decreases as the beam is shifted farther from the sphere, most of that energy is in the lowest-order mode.

  18. Room acoustics analysis using circular arrays: an experimental study based on sound field plane-wave decomposition.

    PubMed

    Torres, Ana M; Lopez, Jose J; Pueo, Basilio; Cobos, Maximo

    2013-04-01

    Plane-wave decomposition (PWD) methods using microphone arrays have been shown to be a very useful tool within the applied acoustics community for their multiple applications in room acoustics analysis and synthesis. While many theoretical aspects of PWD have been previously addressed in the literature, the practical advantages of the PWD method to assess the acoustic behavior of real rooms have been barely explored so far. In this paper, the PWD method is employed to analyze the sound field inside a selected set of real rooms having a well-defined purpose. To this end, a circular microphone array is used to capture and process a number of impulse responses at different spatial positions, providing angle-dependent data for both direct and reflected wavefronts. The detection of reflected plane waves is performed by means of image processing techniques applied over the raw array response data and over the PWD data, showing the usefulness of image-processing-based methods for room acoustics analysis.

  19. Extension of the basis set of linearized augmented plane wave (LAPW) method by using supplemented tight binding basis functions

    NASA Astrophysics Data System (ADS)

    Nikolaev, A. V.; Lamoen, D.; Partoens, B.

    2016-07-01

    In order to increase the accuracy of the linearized augmented plane wave (LAPW) method, we present a new approach where the plane wave basis function is augmented by two different atomic radial components constructed at two different linearization energies corresponding to two different electron bands (or energy windows). We demonstrate that this case can be reduced to the standard treatment within the LAPW paradigm where the usual basis set is enriched by the basis functions of the tight binding type, which go to zero with zero derivative at the sphere boundary. We show that the task is closely related with the problem of extended core states which is currently solved by applying the LAPW method with local orbitals (LAPW+LO). In comparison with LAPW+LO, the number of supplemented basis functions in our approach is doubled, which opens up a new channel for the extension of the LAPW and LAPW+LO basis sets. The appearance of new supplemented basis functions absent in the LAPW+LO treatment is closely related with the existence of the u ˙ l -component in the canonical LAPW method. We discuss properties of additional tight binding basis functions and apply the extended basis set for computation of electron energy bands of lanthanum (face and body centered structures) and hexagonal close packed lattice of cadmium. We demonstrate that the new treatment gives lower total energies in comparison with both canonical LAPW and LAPW+LO, with the energy difference more pronounced for intermediate and poor LAPW basis sets.

  20. Electron transport in graphene/graphene side-contact junction by plane-wave multiple-scattering method

    SciTech Connect

    Li, Xiang-Guo; Chu, Iek-Heng; Zhang, X. -G.; Cheng, Hai-Ping

    2015-05-28

    Electron transport in graphene is along the sheet but junction devices are often made by stacking different sheets together in a “side-contact” geometry which causes the current to flow perpendicular to the sheets within the device. Such geometry presents a challenge to first-principles transport methods. We solve this problem by implementing a plane-wave-based multiple-scattering theory for electron transport. In this study, this implementation improves the computational efficiency over the existing plane-wave transport code, scales better for parallelization over large number of nodes, and does not require the current direction to be along a lattice axis. As a first application, we calculate the tunneling current through a side-contact graphene junction formed by two separate graphene sheets with the edges overlapping each other. We find that transport properties of this junction depend strongly on the AA or AB stacking within the overlapping region as well as the vacuum gap between two graphene sheets. Finally, such transport behaviors are explained in terms of carbon orbital orientation, hybridization, and delocalization as the geometry is varied.

  1. Correction of the near threshold behavior of electron collisional excitation cross-sections in the plane-wave Born approximation

    SciTech Connect

    Kilcrease, D. P.; Brookes, S.

    2013-08-19

    The modeling of NLTE plasmas requires the solution of population rate equations to determine the populations of the various atomic levels relevant to a particular problem. The equations require many cross sections for excitation, de-excitation, ionization and recombination. Additionally, a simple and computational fast way to calculate electron collisional excitation cross-sections for ions is by using the plane-wave Born approximation. This is essentially a high-energy approximation and the cross section suffers from the unphysical problem of going to zero near threshold. Various remedies for this problem have been employed with varying degrees of success. We present a correction procedure for the Born cross-sections that employs the Elwert–Sommerfeld factor to correct for the use of plane waves instead of Coulomb waves in an attempt to produce a cross-section similar to that from using the more time consuming Coulomb Born approximation. We compare this new approximation with other, often employed correction procedures. Furthermore, we also look at some further modifications to our Born Elwert procedure and its combination with Y.K. Kim's correction of the Coulomb Born approximation for singly charged ions that more accurately approximate convergent close coupling calculations.

  2. Terahertz Wide-Angle Imaging and Analysis on Plane-wave Criteria Based on Inverse Synthetic Aperture Techniques

    NASA Astrophysics Data System (ADS)

    Gao, Jing Kun; Qin, Yu Liang; Deng, Bin; Wang, Hong Qiang; Li, Jin; Li, Xiang

    2016-04-01

    This paper presents two parts of work around terahertz imaging applications. The first part aims at solving the problems occurred with the increasing of the rotation angle. To compensate for the nonlinearity of terahertz radar systems, a calibration signal acquired from a bright target is always used. Generally, this compensation inserts an extra linear phase term in the intermediate frequency (IF) echo signal which is not expected in large-rotation angle imaging applications. We carried out a detailed theoretical analysis on this problem, and a minimum entropy criterion was employed to estimate and compensate for the linear-phase errors. In the second part, the effects of spherical wave on terahertz inverse synthetic aperture imaging are analyzed. Analytic criteria of plane-wave approximation were derived in the cases of different rotation angles. Experimental results of corner reflectors and an aircraft model based on a 330-GHz linear frequency-modulated continuous wave (LFMCW) radar system validated the necessity and effectiveness of the proposed compensation. By comparing the experimental images obtained under plane-wave assumption and spherical-wave correction, it also showed to be highly consistent with the analytic criteria we derived.

  3. Pseudopotential treatment of two aligned dipoles under external harmonic confinement

    SciTech Connect

    Kanjilal, K.; Bohn, John L.; Blume, D.

    2007-05-15

    Dipolar Bose and Fermi gases, which are currently being studied extensively experimentally and theoretically, interact through anisotropic, long-range potentials. Here, we replace the long-range potential by a zero-range pseudopotential that simplifies the theoretical treatment of two dipolar particles in a harmonic trap. Our zero-range pseudopotential description reproduces the energy spectrum of two dipoles interacting through a shape-dependent potential under external confinement very well, provided that sufficiently many partial waves are included, and readily leads to a classification scheme of the energy spectrum in terms of approximate angular momentum quantum numbers. The results may be directly relevant to the physics of dipolar gases loaded into optical lattices.

  4. The electrical transport properties of liquid Rb using pseudopotential theory

    NASA Astrophysics Data System (ADS)

    Patel, A. B.; Bhatt, N. K.; Thakore, B. Y.; Vyas, P. R.; Jani, A. R.

    2014-04-01

    Certain electric transport properties of liquid Rb are reported. The electrical resistivity is calculated by using the self-consistent approximation as suggested by Ferraz and March. The pseudopotential due to Hasegawa et al for full electron-ion interaction, which is valid for all electrons and contains the repulsive delta function due to achieve the necessary s-pseudisation was used for the calculation. Temperature dependence of structure factor is considered through temperature dependent potential parameter in the pair potential. Finally, thermo-electric power and thermal conductivity are obtained. The outcome of the present study is discussed in light of other such results, and confirms the applicability of pseudopotential at very high temperature via temperature dependent pair potential.

  5. Surface properties of simple metals in a structureless pseudopotential model

    NASA Astrophysics Data System (ADS)

    Kiejna, Adam

    1993-03-01

    The structureless pseudopotential model of Perdew, Tran, and Smith [Phys. Rev. B 42, 11 627 (1990)] is applied to determine surface properties of Al, Mg, Pb, Zn, and alkali metals. Results of self-consistent Kohn-Sham calculations of surface energies, work functions, and the location of the image plane both for a flat-metal (uncorrugated) surface and for the exposed single-crystal faces are presented. In contrast to jellium, the calculated distance from the image-plane position to the uniform positive background edge increases with the decreasing mean electron density in the bulk metal. The calculated surface energies show more realistic weaker face dependence compared to the previous perturbational or variational calculations of this type and agree well with those predicted by the second-order pseudopotential perturbation theory.

  6. The electrical transport properties of liquid Rb using pseudopotential theory

    SciTech Connect

    Patel, A. B. Bhatt, N. K. Thakore, B. Y. Jani, A. R.; Vyas, P. R.

    2014-04-24

    Certain electric transport properties of liquid Rb are reported. The electrical resistivity is calculated by using the self-consistent approximation as suggested by Ferraz and March. The pseudopotential due to Hasegawa et al for full electron-ion interaction, which is valid for all electrons and contains the repulsive delta function due to achieve the necessary s-pseudisation was used for the calculation. Temperature dependence of structure factor is considered through temperature dependent potential parameter in the pair potential. Finally, thermo-electric power and thermal conductivity are obtained. The outcome of the present study is discussed in light of other such results, and confirms the applicability of pseudopotential at very high temperature via temperature dependent pair potential.

  7. Nonlocal modification of Newtonian gravity

    SciTech Connect

    Blome, Hans-Joachim; Chicone, Carmen; Hehl, Friedrich W.; Mashhoon, Bahram

    2010-03-15

    The Newtonian regime of a recent nonlocal extension of general relativity is investigated. Nonlocality is introduced via a scalar ''constitutive'' kernel in a special case of the translational gauge theory of gravitation, namely, the teleparallel equivalent of general relativity. In this theory, the nonlocal aspect of gravity simulates dark matter. A nonlocal and nonlinear generalization of Poisson's equation of Newtonian gravitation is presented. The implications of nonlocality for the gravitational physics in the solar system are briefly studied.

  8. Irradiance-variance behavior by numerical simulation for plane-wave and spherical-wave optical propagation through strong turbulence

    PubMed

    Flatte; Gerber

    2000-06-01

    We have simulated optical propagation through atmospheric turbulence in which the spectrum near the inner scale follows that of Hill and Clifford [J. Opt. Soc. Am. 68, 892 (1978)] and the turbulence strength puts the propagation into the asymptotic strong-fluctuation regime. Analytic predictions for this regime have the form of power laws as a function of beta0(2), the irradiance variance predicted by weak-fluctuation (Rytov) theory, and l0, the inner scale. The simulations indeed show power laws for both spherical-wave and plane-wave initial conditions, but the power-law indices are dramatically different from the analytic predictions. Let sigmaI(2) - 1 = a(beta0(2)/betac(2))-b(l0/Rf)c, where we take the reference value of beta0(2) to be betac(2) = 60.6, because this is the center of our simulation region. For zero inner scale (for which c = 0), the analytic prediction is b = 0.4 and a = 0.17 (0.37) for a plane (spherical) wave. Our simulations for a plane wave give a = 0.234 +/- 0.007 and b = 0.50 +/- 0.07, and for a spherical wave they give a = 0.58 + /- 0.01 and b = 0.65 +/- 0.05. For finite inner scale the analytic prediction is b = 1/6, c = 7/18 and a = 0.76 (2.07) for a plane (spherical) wave. We find that to a reasonable approximation the behavior with beta0(2) and l0 indeed factorizes as predicted, and each part behaves like a power law. However, our simulations for a plane wave give a = 0.57 +/- 0.03, b = 0.33 +/- 0.03, and c = 0.45 +/- 0.06. For spherical waves we find a = 3.3 +/- 0.3, b = 0.45 +/- 0.05, and c = 0.8 +/- 0.1.

  9. Multipartite nonlocality distillation

    SciTech Connect

    Hsu, Li-Yi; Wu, Keng-Shuo

    2010-11-15

    The stronger nonlocality than that allowed in quantum theory can provide an advantage in information processing and computation. Since quantum entanglement is distillable, can nonlocality be distilled in the nonsignalling condition? The answer is positive in the bipartite case. In this article the distillability of the multipartite nonlocality is investigated. We propose a distillation protocol solely exploiting xor operations on output bits. The probability-distribution vectors and matrix are introduced to tackle the correlators. It is shown that only the correlators with extreme values can survive the distillation process. As the main result, the amplified nonlocality cannot maximally violate any Bell-type inequality. Accordingly, a distillability criterion in the postquantum region is proposed.

  10. Making space for nonlocality

    NASA Astrophysics Data System (ADS)

    Millen, James

    2016-04-01

    George Musser's book Spooky Action at a Distance focuses on one of quantum physics' more challenging concepts, nonlocality, and its multitude of implications, particularly its assault on space itself.

  11. Theory of surface second-harmonic generation for semiconductors including effects of nonlocal operators

    NASA Astrophysics Data System (ADS)

    Anderson, Sean M.; Tancogne-Dejean, Nicolas; Mendoza, Bernardo S.; Véniard, Valérie

    2015-02-01

    We formulate a theoretical approach of surface second-harmonic generation from semiconductor surfaces based on the length gauge and the electron density operator. Within the independent particle approximation, the nonlinear second-order surface susceptibility tensor χa b c(-2 ω ;ω ,ω ) is calculated, including in one unique formulation (i) the scissors correction, needed to have the correct value of the energy band gap, (ii) the contribution of the nonlocal part of the pseudopotentials, routinely used in ab initio band-structure calculations, and (iii) the derivation for the inclusion of the cut function, used to extract the surface response. The first two contributions are described by spatially nonlocal quantum-mechanical operators and are fully taken into account in the present formulation. As a test case of the approach, we calculate χx x x(-2 ω ;ω ,ω ) for the clean Si (001 )2 ×1 reconstructed surface. The effects of the scissors correction and of the nonlocal part of the pseudopotentials are discussed in surface nonlinear optics. The scissors correction shifts the spectrum to higher energies though the shifting is not rigid and mixes the 1 ω and 2 ω resonances, and has a strong influence in the line shape. The effects of the nonlocal part of the pseudopotentials keeps the same line shape of | χ2×1 x x x(-2 ω ;ω ,ω ) | , but reduces its value by 15%-20%. Therefore the inclusion of the three aforementioned contributions is very important and makes our scheme unprecedented and opens the possibility to study surface second-harmonic generation with more versatility and providing more accurate results.

  12. Coherent quantum states of a relativistic particle in an electromagnetic plane wave and a parallel magnetic field

    SciTech Connect

    Colavita, E.; Hacyan, S.

    2014-03-15

    We analyze the solutions of the Klein–Gordon and Dirac equations describing a charged particle in an electromagnetic plane wave combined with a magnetic field parallel to the direction of propagation of the wave. It is shown that the Klein–Gordon equation admits coherent states as solutions, while the corresponding solutions of the Dirac equation are superpositions of coherent and displaced-number states. Particular attention is paid to the resonant case in which the motion of the particle is unbounded. -- Highlights: •We study a relativistic electron in a particular electromagnetic field configuration. •New exact solutions of the Klein–Gordon and Dirac equations are obtained. •Coherent and displaced number states can describe a relativistic particle.

  13. Angular spectral plane-wave expansion of nonstationary random fields in stochastic mode-stirred reverberation processes.

    PubMed

    Arnaut, Luk R

    2010-04-01

    We derive an integral expression for the plane-wave expansion of the time-varying (nonstationary) random field inside a mode-stirred reverberation chamber. It is shown that this expansion is a so-called oscillatory process, whose kernel can be expressed explicitly in closed form. The effect of nonstationarity is a modulation of the spectral density of the field on a time scale that is a function of the cavity relaxation time. It is also shown how the contribution by a nonzero initial value of the field can be incorporated into the expansion. The results are extended to a special class of second-order processes, relevant to the reception of a mode-stirred reverberation field by a device under test with a first-order (relaxation-type) frequency response.

  14. Plane-wave expansion method for calculating band structure of photonic crystal slabs with perfectly matched layers.

    PubMed

    Shi, Shouyuan; Chen, Caihua; Prather, Dennis W

    2004-09-01

    We present a new algorithm for calculation of the band structure of photonic crystal slabs. This algorithm combines the plane-wave expansion method with perfectly matched layers for the termination of the computational region in the direction out of the plane. In addition, the effective-medium tensor is applied to improve convergence. A general complex eigenvalue problem is then obtained. Two criteria are presented to distinguish the guided modes from the PML modes. As such, this scheme can accurately determine the band structure both above and below the light cone. The convergence of the algorithm presented has been studied. The results obtained by using this algorithm have been compared with those obtained by the finite-difference time-domain method and found to agree very well.

  15. Fourier factorization with complex polarization bases in the plane-wave expansion method applied to two-dimensional photonic crystals.

    PubMed

    Antos, Roman; Veis, Martin

    2010-12-20

    We demonstrate an enhancement of the plane wave expansion method treating two-dimensional photonic crystals by applying Fourier factorization with generally elliptic polarization bases. By studying three examples of periodically arranged cylindrical elements, we compare our approach to the classical Ho method in which the permittivity function is simply expanded without changing coordinates, and to the normal vector method using a normal-tangential polarization transform. The compared calculations clearly show that our approach yields the best convergence properties owing to the complete continuity of our distribution of polarization bases. The presented methodology enables us to study more general systems such as periodic elements with an arbitrary cross-section or devices such as photonic crystal waveguides. PMID:21197026

  16. Exact off-resonance near fields of small-size extended hemielliptic 2-D lenses illuminated by plane waves.

    PubMed

    Boriskin, Artem V; Sauleau, Ronan; Nosich, Alexander I

    2009-02-01

    The near fields of small-size extended hemielliptic lenses made of rexolite and isotropic quartz and illuminated by E- and H-polarized plane waves are studied. Variations in the focal domain size, shape, and location are reported versus the angle of incidence of the incoming wave. The problem is solved numerically in a two-dimensional formulation. The accuracy of results is guaranteed by using a highly efficient numerical algorithm based on the combination of the Muller boundary integral equations, the method of analytical regularization, and the trigonometric Galerkin discretization scheme. The analysis fully accounts for the finite size of the lens as well as its curvature and thus can be considered as a reference solution for other electromagnetic solvers. Moreover, the trusted description of the focusing ability of a finite-size hemielliptic lens can be useful in the design of antenna receivers.

  17. Phase and direction dependence of photorefraction in a low-frequency strong circular-polarized plane wave

    NASA Astrophysics Data System (ADS)

    Huang, Yong-Sheng; Wang, Nai-Yan; Tang, Xiu-Zhang

    2015-05-01

    Contrary to the superposition principle, it is well known that photorefraction exists in the vacuum with the presence of a strong static field, a laser field, or a rotational magnetic field. Different from the classical optical crystals, the refractive index also depends on the phase of the strong electromagnetic field. We obtain the phase and direction dependence of the refractive index of a probe wave incident in the strong field of a circular-polarized plane wave by solving the Maxwell equations corrected by the effective Lagrangian. It may provide a valuable theoretical basis to calculate the polarization evolution of waves in the strong electromagnetic circumstances of pulsar or neutron stars. Project supported by the National Basic Research Program of China (Grant No. 2011CB808104) and the National Natural Science Foundation of China (Grant No. 11105233).

  18. Fourier factorization with complex polarization bases in the plane-wave expansion method applied to two-dimensional photonic crystals.

    PubMed

    Antos, Roman; Veis, Martin

    2010-12-20

    We demonstrate an enhancement of the plane wave expansion method treating two-dimensional photonic crystals by applying Fourier factorization with generally elliptic polarization bases. By studying three examples of periodically arranged cylindrical elements, we compare our approach to the classical Ho method in which the permittivity function is simply expanded without changing coordinates, and to the normal vector method using a normal-tangential polarization transform. The compared calculations clearly show that our approach yields the best convergence properties owing to the complete continuity of our distribution of polarization bases. The presented methodology enables us to study more general systems such as periodic elements with an arbitrary cross-section or devices such as photonic crystal waveguides.

  19. Mobile Ultrasound Plane Wave Beamforming on iPhone or iPad using Metal- based GPU Processing

    NASA Astrophysics Data System (ADS)

    Hewener, Holger J.; Tretbar, Steffen H.

    Mobile and cost effective ultrasound devices are being used in point of care scenarios or the drama room. To reduce the costs of such devices we already presented the possibilities of consumer devices like the Apple iPad for full signal processing of raw data for ultrasound image generation. Using technologies like plane wave imaging to generate a full image with only one excitation/reception event the acquisition times and power consumption of ultrasound imaging can be reduced for low power mobile devices based on consumer electronics realizing the transition from FPGA or ASIC based beamforming into more flexible software beamforming. The massive parallel beamforming processing can be done with the Apple framework "Metal" for advanced graphics and general purpose GPU processing for the iOS platform. We were able to integrate the beamforming reconstruction into our mobile ultrasound processing application with imaging rates up to 70 Hz on iPad Air 2 hardware.

  20. Angular spectral plane-wave expansion of nonstationary random fields in stochastic mode-stirred reverberation processes

    NASA Astrophysics Data System (ADS)

    Arnaut, Luk R.

    2010-04-01

    We derive an integral expression for the plane-wave expansion of the time-varying (nonstationary) random field inside a mode-stirred reverberation chamber. It is shown that this expansion is a so-called oscillatory process, whose kernel can be expressed explicitly in closed form. The effect of nonstationarity is a modulation of the spectral density of the field on a time scale that is a function of the cavity relaxation time. It is also shown how the contribution by a nonzero initial value of the field can be incorporated into the expansion. The results are extended to a special class of second-order processes, relevant to the reception of a mode-stirred reverberation field by a device under test with a first-order (relaxation-type) frequency response.

  1. Expressions for Form Factors for Inelastic Scattering and Charge Exchange in Plane-Wave, Distorted-Wave, and Coupled-Channels Reaction Formalisms

    SciTech Connect

    Dietrich, F S

    2006-09-25

    This document is intended to facilitate calculation of inelastic scattering and charge-exchange cross sections in a variety of reaction models, including the plane-wave and distorted-wave approximations and the full coupled-channels treatments. Expressions are given for the coupling potentials between the relevant channels in both coordinate and momentum space. In particular, it is expected that the plane-wave calculations should be useful as a check on the correctness of coupled-channels calculations. The Fourier transform methods used to calculate the plane-wave approximation cross sections are also intended to be used to generate the transition potentials for coupled-channels codes, using a folding model with local effective interactions. Specific expressions are given for calculating transition densities for the folding model in the random phase approximation (RPA).

  2. Electromagnetic scattering by a buried sphere in a lossy medium of an inhomogeneous plane wave at arbitrary incidence: spectral-domain method.

    PubMed

    Frezza, F; Mangini, F

    2016-05-01

    A rigorous theoretical treatment to analyze the electromagnetic scattering of an inhomogeneous elliptically polarized plane wave by a sphere buried in a lossy half-space is presented. To consider the losses in the media an inhomogeneous plane wave is considered. The incident and the scattered electric field components are expanded in series of vectorial spherical harmonics using the Legendre functions generalized via hypergeometrical and gamma functions, with unknown expansion coefficients. The spectral-domain method to represent the scattered electric field is used in order to compute the scattered-reflected and scattered-transmitted fields, considering the reflection and transmission of each elementary plane wave by the interface. Finally, the unknown coefficients of the scattered field are computed by imposing the boundary condition on the spherical surface. In order to validate the model, a homemade code has been implemented. Comparisons with the simulations performed with a commercial software and the results in the literature are presented.

  3. Electromagnetic scattering by a buried sphere in a lossy medium of an inhomogeneous plane wave at arbitrary incidence: spectral-domain method.

    PubMed

    Frezza, F; Mangini, F

    2016-05-01

    A rigorous theoretical treatment to analyze the electromagnetic scattering of an inhomogeneous elliptically polarized plane wave by a sphere buried in a lossy half-space is presented. To consider the losses in the media an inhomogeneous plane wave is considered. The incident and the scattered electric field components are expanded in series of vectorial spherical harmonics using the Legendre functions generalized via hypergeometrical and gamma functions, with unknown expansion coefficients. The spectral-domain method to represent the scattered electric field is used in order to compute the scattered-reflected and scattered-transmitted fields, considering the reflection and transmission of each elementary plane wave by the interface. Finally, the unknown coefficients of the scattered field are computed by imposing the boundary condition on the spherical surface. In order to validate the model, a homemade code has been implemented. Comparisons with the simulations performed with a commercial software and the results in the literature are presented. PMID:27140892

  4. Effects on the Electromagnetic Scattering of a Plane Wave due to the Surface Roughness of a Buried Perfectly Conducting Pipeline

    NASA Astrophysics Data System (ADS)

    Frezza, Fabrizio; Mangini, Fabio; Stoja, Endri; Tedeschi, Nicola

    2013-04-01

    In this work we present a numerical study of the effects that can be observed in the electromagnetic scattering of a plane wave due to the surface roughness of a buried scatterer. The latter is supposed to be a metallic pipeline modeled as a perfect-electric conducting cylinder immersed in a half-space occupied by a lossy medium. Considering the pipeline's cross-section, the surface roughness is modeled as a sinusoidal variation of the radius of the cylinder's surface with respect to the revolution angle. A linearly-polarized plane wave impinging normally to the interface between air and the previously-mentioned medium excites the structure. As a result, we monitor the three components of the scattered electric field along a line just above the interface between the two media. To perform the study, a commercially available simulator which implements the Finite Element Method was adopted. In order to discriminate the effects due only to the surface roughness, we compare the results obtained by the rough surface scatterers with the reference case of a perfect cylinder in which the surface roughness is absent, for a fixed depth and a fixed mean radius of the cylinder. In our study, we vary the amplitude and the angular frequency of the sinusoidal disturbance to model different surface roughness scenarios. For all the scenarios taken in consideration, a frequency sweep of the impinging radiation is performed. This allows us to investigate the relation between the excitation frequency and the sinusoidal disturbance frequency of the rough surface. The study has several implications in the field of civil engineering. One example might be the one in which the geometrical characteristics of the buried pipeline are known in advance, and it is important to continuously monitor the structural variations of its external surface due to the deterioration in time under the action of various environmental factors.

  5. Analytic projection from plane-wave and PAW wavefunctions and application to chemical-bonding analysis in solids.

    PubMed

    Maintz, Stefan; Deringer, Volker L; Tchougréeff, Andrei L; Dronskowski, Richard

    2013-11-01

    Quantum-chemical computations of solids benefit enormously from numerically efficient plane-wave (PW) basis sets, and together with the projector augmented-wave (PAW) method, the latter have risen to one of the predominant standards in computational solid-state sciences. Despite their advantages, plane waves lack local information, which makes the interpretation of local densities-of-states (DOS) difficult and precludes the direct use of atom-resolved chemical bonding indicators such as the crystal orbital overlap population (COOP) and the crystal orbital Hamilton population (COHP) techniques. Recently, a number of methods have been proposed to overcome this fundamental issue, built around the concept of basis-set projection onto a local auxiliary basis. In this work, we propose a novel computational technique toward this goal by transferring the PW/PAW wavefunctions to a properly chosen local basis using analytically derived expressions. In particular, we describe a general approach to project both PW and PAW eigenstates onto given custom orbitals, which we then exemplify at the hand of contracted multiple-ζ Slater-type orbitals. The validity of the method presented here is illustrated by applications to chemical textbook examples-diamond, gallium arsenide, the transition-metal titanium-as well as nanoscale allotropes of carbon: a nanotube and the C60 fullerene. Remarkably, the analytical approach not only recovers the total and projected electronic DOS with a high degree of confidence, but it also yields a realistic chemical-bonding picture in the framework of the projected COHP method. PMID:24022911

  6. A generalized nonlocal vector calculus

    NASA Astrophysics Data System (ADS)

    Alali, Bacim; Liu, Kuo; Gunzburger, Max

    2015-10-01

    A nonlocal vector calculus was introduced in Du et al. (Math Model Meth Appl Sci 23:493-540, 2013) that has proved useful for the analysis of the peridynamics model of nonlocal mechanics and nonlocal diffusion models. A formulation is developed that provides a more general setting for the nonlocal vector calculus that is independent of particular nonlocal models. It is shown that general nonlocal calculus operators are integral operators with specific integral kernels. General nonlocal calculus properties are developed, including nonlocal integration by parts formula and Green's identities. The nonlocal vector calculus introduced in Du et al. (Math Model Meth Appl Sci 23:493-540, 2013) is shown to be recoverable from the general formulation as a special example. This special nonlocal vector calculus is used to reformulate the peridynamics equation of motion in terms of the nonlocal gradient operator and its adjoint. A new example of nonlocal vector calculus operators is introduced, which shows the potential use of the general formulation for general nonlocal models.

  7. Ab-initio modeling of an anion C- 60 pseudopotential for fullerene-based compounds

    NASA Astrophysics Data System (ADS)

    Vrubel, Ivan I.; Polozkov, Roman G.; Ivanov, Vadim K.

    2016-08-01

    An anion C- 60 pseudopotential is determined from an ab-initio-based approach. First, ab-initio calculations are performed to calculate the electronic charge density and the total electrostatic potential. Second, the effective dependence of the pseudopotential on the radial degree of freedom is extracted from the angular average of the total electrostatic potential. Finally, the resulting effective pseudopotential is fitted to a simple analytical form which can be applied in further dynamical simulations of fullerene-based compounds.

  8. Analytically reduced form for the class of integrals containing multicenter products of 1s hydrogenic orbitals, Coulomb or Yukawa potentials, and plane waves

    NASA Technical Reports Server (NTRS)

    Straton, Jack C.

    1989-01-01

    The class of integrals containing the product of N 1s hydrogenic orbitals and M Coulomb or Yukawa potentials with m plane waves is investigated analytically. The results obtained by Straton (1989) are extended and generalized. It is shown that the dimensionality of the entire class can be reduced from 3m to M+N-1.

  9. Nonlocal N=1 supersymmetry

    NASA Astrophysics Data System (ADS)

    Kimura, Tetsuji; Mazumdar, Anupam; Noumi, Toshifumi; Yamaguchi, Masahide

    2016-10-01

    We construct N=1 supersymmetric nonlocal theories in four dimension. We discuss higher derivative extensions of chiral and vector superfields, and write down generic forms of Kähler potential and superpotential up to quadratic order. We derive the condition in which an auxiliary field remains non-dynamical, and the dynamical scalars and fermions are free from the ghost degrees of freedom. We also investigate the nonlocal effects on the supersymmetry breaking and find that supertrace (mass) formula is significantly modified even at the tree level.

  10. IDO Scheme for Accurate Computation of Seismic Waves I. Plane-Wave Response of a Vertically Heterogeneous Medium

    NASA Astrophysics Data System (ADS)

    Ohkawauchi, K.; Takenaka, H.

    2006-12-01

    We propose a new method for the calculation of seismic wave propagation using the interpolated differential operator (IDO, Aoki,1997) which is a numerical method for solving the partial differential equations and is based on a high accurate interpolation of the profile for the independent variables over a local area. It improves the accuracy of wave computation with high accuracy because the local interpolation can represent high order behavior of wave field between grid points. In addition, locality of this approach makes possible treatment of boundary conditions exactly. In this study, we address computation of plane-wave responses of vertically heterogeneous structure models. We then solve the elastodynamic equation for plane wave derived by Tanaka and Takenaka (2005). The equations to be solved in our method are not only velocity-stress equations but also the corresponding ones integrated over each cell between adjacent grid points. We use two staggered-grid systems which can be non-uniform, and then discretize the governing equations using a finite-difference scheme of second-order accurate in time, and the second-order Hermite interpolation in space. In this method, the second-order Hermite interpolation of particle velocity or stress is obtained from the values at the adjacent two grid points and the integration value at the cell between the grid points. The time marching of the original and integrated quantities are proceeded, and in the following time step the quantities are computed on the alternative grid system to that used in the current time step. In implementation of a free-surface boundary condition, all field quantities locate just on the free surface. Their computational accuracy is the same order as those in the other spatial domain. We also implement the interface condition in a similarly way to the free surface condition. We used some simple models to test the scheme. The results showed that the waveforms calculated by our method fit the

  11. Electron Correlation in the Condensed Phase from a Resolution of Identity Approach Based on the Gaussian and Plane Waves Scheme.

    PubMed

    Del Ben, Mauro; Hutter, Jürg; VandeVondele, Joost

    2013-06-11

    The second-order Møller-Plesset perturbation energy (MP2) and the Random Phase Approximation (RPA) correlation energy are increasingly popular post-Kohn-Sham correlation methods. Here, a novel algorithm based on a hybrid Gaussian and Plane Waves (GPW) approach with the resolution-of-identity (RI) approximation is developed for MP2, scaled opposite-spin MP2 (SOS-MP2), and direct-RPA (dRPA) correlation energies of finite and extended system. The key feature of the method is that the three center electron repulsion integrals (μν|P) necessary for the RI approximation are computed by direct integration between the products of Gaussian basis functions μν and the electrostatic potential arising from the RI fitting densities P. The electrostatic potential is obtained in a plane waves basis set after solving the Poisson equation in Fourier space. This scheme is highly efficient for condensed phase systems and offers a particularly easy way for parallel implementation. The RI approximation allows to speed up the MP2 energy calculations by a factor 10 to 15 compared to the canonical implementation but still requires O(N(5)) operations. On the other hand, the combination of RI with a Laplace approach in SOS-MP2 and an imaginary frequency integration in dRPA reduces the computational effort to O(N(4)) in both cases. In addition to that, our implementations have low memory requirements and display excellent parallel scalability up to tens of thousands of processes. Furthermore, exploiting graphics processing units (GPU), a further speedup by a factor ∼2 is observed compared to the standard only CPU implementations. In this way, RI-MP2, RI-SOS-MP2, and RI-dRPA calculations for condensed phase systems containing hundreds of atoms and thousands of basis functions can be performed within minutes employing a few hundred hybrid nodes. In order to validate the presented methods, various molecular crystals have been employed as benchmark systems to assess the performance, while

  12. Teaching Quantum Nonlocality

    ERIC Educational Resources Information Center

    Hobson, Art

    2012-01-01

    Nonlocality arises from the unified "all or nothing" interactions of a spatially extended field quantum such as a photon or an electron. In the double-slit experiment with light, for example, each photon comes through both slits and arrives at the viewing screen as an extended but unified energy bundle or "field quantum." When the photon interacts…

  13. Analytical expressions for the log-amplitude correlation function of a plane wave through anisotropic atmospheric refractive turbulence.

    PubMed

    Gudimetla, V S Rao; Holmes, Richard B; Smith, Carey; Needham, Gregory

    2012-05-01

    The effect of anisotropic Kolmogorov turbulence on the log-amplitude correlation function for plane-wave fields is investigated using analysis, numerical integration, and simulation. A new analytical expression for the log-amplitude correlation function is derived for anisotropic Kolmogorov turbulence. The analytic results, based on the Rytov approximation, agree well with a more general wave-optics simulation based on the Fresnel approximation as well as with numerical evaluations, for low and moderate strengths of turbulence. The new expression reduces correctly to previously published analytic expressions for isotropic turbulence. The final results indicate that, as asymmetry becomes greater, the Rytov variance deviates from that given by the standard formula. This deviation becomes greater with stronger turbulence, up to moderate turbulence strengths. The anisotropic effects on the log-amplitude correlation function are dominant when the separation of the points is within the Fresnel length. In the direction of stronger turbulence, there is an enhanced dip in the correlation function at a separation close to the Fresnel length. The dip is diminished in the weak-turbulence axis, suggesting that energy redistribution via focusing and defocusing is dominated by the strong-turbulence axis. The new analytical expression is useful when anisotropy is observed in relevant experiments.

  14. Assessment of induced SAR in children exposed to electromagnetic plane waves between 10 MHz and 5.6 GHz

    NASA Astrophysics Data System (ADS)

    Bakker, J. F.; Paulides, M. M.; Christ, A.; Kuster, N.; van Rhoon, G. C.

    2010-06-01

    To avoid potentially adverse health effects of electromagnetic fields (EMF), the International Commission on Non-Ionizing Radiation Protection (ICNIRP) has defined EMF reference levels from the basic restrictions on the induced whole-body-averaged specific absorption rate (SARwb) and the peak 10 g spatial-averaged SAR (SAR10g). The objective of this study is to assess if the SAR in children remains below the basic restrictions upon exposure at the reference levels. Finite difference time domain (FDTD) modeling was used to calculate the SAR in six children and two adults when exposed to all 12 orthogonal plane wave configurations. A sensitivity study showed an expanded uncertainty of 53% (SARwb) and 58% (SAR10g) due to variations in simulation settings and tissue properties. In this study, we found that the basic restriction on the SARwb is occasionally exceeded for children, up to a maximum of 45% in small children. The maximum SAR10g values, usually found at body protrusions, remain under the limit for all scenarios studied. Our results are in good agreement with the literature, suggesting that the recommended ICNIRP reference levels may need fine tuning.

  15. Saturation and the limit of jet mixing enhancement by single frequency plane wave excitation - Experiment and theory

    NASA Technical Reports Server (NTRS)

    Raman, Ganesh; Rice, Edward J.; Mankbadi, Reda R.

    1988-01-01

    The limitations of single frequency plane wave excitation in mixing enhancement are investigated for a circular jet. Measurements made in an 8.8 cm diameter jet are compared with a theoretical model. The measurements are made to quantify mixing at excitation amplitudes up to 2 percent of the jet exit velocity. The initial boundary layer state, the exit mean and fluctuating velocity profiles and spectra are documented for all cases considered. The amplitude of the fundamental wave is recorded along the jet axis for various levels of excitation. As the amplitude of excitation is increased the jet spreading rate is increased, but beyond a saturation amplitude further increases have no effect on the spreading. The experimental results are compared with theoretical estimates. In the theory the flow is split into the mean flow, large scale motions, and fine scale turbulence. Shape assumptions for the mean flow, and fine scale turbulence along with the shape for the large scale motions obtained from a linear stability theory provide the closure. The experimental results compare reasonably well with predictions.

  16. Saturation and the limit of jet mixing enhancement by single frequency plane wave excitation: Experiment and theory

    NASA Technical Reports Server (NTRS)

    Raman, Ganesh; Rice, Edward J.; Mankbadi, Reda R.

    1988-01-01

    The limitations of single frequency plane wave excitation in mixing enhancement are investigated for a circular jet. Measurements made in an 8.8 cm diameter jet are compared with a theoretical model. The measurements are made to quantify mixing at excitation amplitudes up to 2 percent of the jet exit velocity. The initial boundary layer state, the exit mean and fluctuating velocity profiles and spectra are documented for all cases considered. The amplitude of the fundamental wave is recorded along the jet axis for various levels of excitation. As the amplitude of excitation is increased the jet spreading rate is increased, but beyond a saturation amplitude further increases have no effect on the spreading. The experimental results are compared with theoretical estimates. In the theory the flow is split into the mean flow, large scale motions, and fine scale turbulence. Shape assumptions for the mean flow, and fine scale turbulence along with the shape for the large scale motions obtained from a linear stability theory provide the closure. The experimental results compare reasonably well with predictions.

  17. Scaling of plane-wave Born cross sections for electron-impact excitation of neutral atoms and molecules

    NASA Astrophysics Data System (ADS)

    Tanaka, Hiroshi

    2015-09-01

    We review the scaling of plane-wave Born cross sections for electron-impact excitation of neutral atoms and molecules. The scaling method is applied to integrated cross sections for electric dipole-allowed transitions. As introduced in the BEB scaling model for ionization cross sections, this scaling replaces the incident electron energy T in the first-order PWB cross sections by T + B + E , where B is the ionization energy, or the binding energy, of the target electron, and E is the excitation energy. Note in a generic form, first-order PWB cross sections are defined as σPWB = (4 πa02 R / T) GOSPWB (T) , where a0 is the Bohr radius, R is the Rydberg energy, and GOS is the Bethe generalized oscillator strength. In the scaling, though two approaches, computational and experimental have been applied, the latter is presented at this meeting in which the Bethe GOS is replaced by the apparent GOS determined by the experiments. Representative examples show that an simple improvement scaled by T + B + E extends the usage of the Born-Bethe approximation into the intermediate region, thereby bridging the gap between the two regions categorized conventionally as slow and fast collisions.

  18. Assessment of induced SAR in children exposed to electromagnetic plane waves between 10 MHz and 5.6 GHz.

    PubMed

    Bakker, J F; Paulides, M M; Christ, A; Kuster, N; van Rhoon, G C

    2010-06-01

    To avoid potentially adverse health effects of electromagnetic fields (EMF), the International Commission on Non-Ionizing Radiation Protection (ICNIRP) has defined EMF reference levels from the basic restrictions on the induced whole-body-averaged specific absorption rate (SAR(wb)) and the peak 10 g spatial-averaged SAR (SAR(10g)). The objective of this study is to assess if the SAR in children remains below the basic restrictions upon exposure at the reference levels. Finite difference time domain (FDTD) modeling was used to calculate the SAR in six children and two adults when exposed to all 12 orthogonal plane wave configurations. A sensitivity study showed an expanded uncertainty of 53% (SAR(wb)) and 58% (SAR(10g)) due to variations in simulation settings and tissue properties. In this study, we found that the basic restriction on the SAR(wb) is occasionally exceeded for children, up to a maximum of 45% in small children. The maximum SAR(10g) values, usually found at body protrusions, remain under the limit for all scenarios studied. Our results are in good agreement with the literature, suggesting that the recommended ICNIRP reference levels may need fine tuning.

  19. E-field extraction from Hx- and Hy- near field values by using plane wave spectrum method

    NASA Astrophysics Data System (ADS)

    Ravelo, B.; Riah, Z.; Baudry, D.; Mazari, B.

    2011-01-01

    This paper deals with a technique for calculating the 3D E-field components knowing only the two components (Hx and Hy) of the H-field in near-zone. The originality of the under study technique lies on the possibility to take into account the evanescent wave influences. The presented E-field extraction process is based on the exploitation of the Maxwell-Ampere relation combined with the plane wave spectrum (PWS) method. The efficiency of the proposed technique is evidenced by comparing the E-field deduced from H-field and the own E-field radiated by the association of electrical- and also magnetic- elementary dipoles in different configurations by using Matlab text programming environment. In addition, as a concrete demonstrator, the concept was also validated with the computation of EM-wave radiated by an open-end microstrip transmission line. As result of comparison, very good agreement between the exact E-field and that one extracted from the H-field was realized by considering the near-field scanned at the height, z = 5 mm and 8 mm above the under test structure at the operating frequency, f = 1 GHz. The presented technique can simplify the difficulties about the E-near-field measurement in EMC applications.

  20. Induced EM field in a layered eccentric spheres model of the head: Plane-wave and localized source exposure

    SciTech Connect

    Skaropoulos, N.C.; Ioannidou, M.P.; Chrissoulidis, D.P.

    1996-10-01

    Understanding the interaction of EM radiation with humans is essential in a number of contemporary applications. Special attention is paid to the absorption of EM energy by the human head, which exhibits a resonant behavior in the frequency band 0.1--3 GHz. The use of handheld transceivers for wireless communications, which operate in close proximity to the head, has raised safety-related questions and questions concerning the effect of the head on the performance of the mobile phone antenna. The induced electromagnetic (EM) field in a layered eccentric spheres structure is determined through a concise analytical formulation based on indirect mode-matching (IMM). The exact analytical solution is applied to a six-layer model of the head. This model allows for eccentricity between the inner and outer sets of concentric spherical layers which simulate brain and skull, respectively. Excitation is provided by a nearby localized source or by an incident plane wave. The numerical application provides information about the total absorbed power, the absorption in each layer, and the spatial distribution of the specific absorption rate (SAR) at frequencies used by cellular phones. The effects of excitation frequency, eccentricity, exposure configuration, and antenna-head separation are investigated.

  1. Simulation of the pressure field beneath a turbulent boundary layer using realizations of uncorrelated wall plane waves.

    PubMed

    Maxit, Laurent

    2016-08-01

    This paper investigates the modeling of a vibrating structure excited by a turbulent boundary layer (TBL). Although the wall pressure field (WPF) of the TBL constitutes a random excitation, the element-based methods generally used for describing complex mechanical structures consider deterministic loads. The response of such structures to a random excitation like TBL is generally deduced from calculations of numerous Frequency Response Functions. Consequently, the process is computationally expansive. To tackle this issue, an efficient process is proposed for generating realizations of the WPF corresponding to the TBL. This process is based on a formulation of the problem in the wavenumber space and the interpretation of the WPF as uncorrelated wall plane waves. Once the WPF has been synthesized, the local vibroacoustic responses are calculated for the different realizations and averaged together in the last step. A numerical application of this process to a plate located beneath a TBL is used to verify its efficiency and ability to reproduce the partial space correlation of the excitation. To further illustrate the proposed method, a stiffened panel modeled using the finite element method is finally examined. PMID:27586754

  2. Tests on novel pseudo-potentials generated from diffusion Monte Carlo data.

    NASA Astrophysics Data System (ADS)

    Reboredo, Fernando; Hood, Randolph; Bajdich, Michal

    2012-02-01

    Since Dmitri Mendeleev developed a table in 1869 to illustrate recurring ("periodic") trends of the elements, it has been understood that most chemical and physical properties can be described by taking into account the outer most electrons of the atoms. These valence electrons are mainly responsible for the chemical bond. In many ab-initio approaches only valence electrons are taken into account and a pseudopotential is used to mimic the response of the core electrons. Typically an all-electron calculation is used to generate a pseudopotential that is used either within density functional theory or quantum chemistry approaches. In this talk we explain and demonstrate a new method to generate pseudopotentials directly from all-electron many-body diffusion Monte Carlo (DMC) calculations and discuss the results of of the transferability of these pseudopotentials. The advantages of incorporating the exchange and correlation directly from DMC into the pseudopotential are also discussed.

  3. Electronic coupling matrix elements from charge constrained density functional theory calculations using a plane wave basis set

    NASA Astrophysics Data System (ADS)

    Oberhofer, Harald; Blumberger, Jochen

    2010-12-01

    We present a plane wave basis set implementation for the calculation of electronic coupling matrix elements of electron transfer reactions within the framework of constrained density functional theory (CDFT). Following the work of Wu and Van Voorhis [J. Chem. Phys. 125, 164105 (2006)], the diabatic wavefunctions are approximated by the Kohn-Sham determinants obtained from CDFT calculations, and the coupling matrix element calculated by an efficient integration scheme. Our results for intermolecular electron transfer in small systems agree very well with high-level ab initio calculations based on generalized Mulliken-Hush theory, and with previous local basis set CDFT calculations. The effect of thermal fluctuations on the coupling matrix element is demonstrated for intramolecular electron transfer in the tetrathiafulvalene-diquinone (Q-TTF-Q-) anion. Sampling the electronic coupling along density functional based molecular dynamics trajectories, we find that thermal fluctuations, in particular the slow bending motion of the molecule, can lead to changes in the instantaneous electron transfer rate by more than an order of magnitude. The thermal average, ( {< {| {H_ab } |^2 } > } )^{1/2} = 6.7 {mH}, is significantly higher than the value obtained for the minimum energy structure, | {H_ab } | = 3.8 {mH}. While CDFT in combination with generalized gradient approximation (GGA) functionals describes the intermolecular electron transfer in the studied systems well, exact exchange is required for Q-TTF-Q- in order to obtain coupling matrix elements in agreement with experiment (3.9 mH). The implementation presented opens up the possibility to compute electronic coupling matrix elements for extended systems where donor, acceptor, and the environment are treated at the quantum mechanical (QM) level.

  4. An investigation of the diffraction of an acoustic plane wave by a curved surface of finite impedance

    NASA Astrophysics Data System (ADS)

    Kearns, James Andrew

    1990-08-01

    The diffraction effects which would occur near the tops of hills and ridges was analyzed. The diffraction of a high frequency plane wave due to its grazing of a two-dimensional curved surface of finite impedance was studied. Laboratory scale models were constructed and measurements were made of the field on, above, and behind either of two curved surfaces possessing distinctly different impedances; that is, one was soft while the other was hard. The experimental technique consisted of simultaneously measuring the pressure at a reference point and at a field point due to a transient pulse generated by an electric spark. The pressure waveforms were digitized and processed. The ratio of the discrete Fourier transforms of the two waveforms provided an estimate of the insertion loss between them. The results of the measurements were compared with the predictions of theory which was derived by Pierce using the method of matched asymptotic expansions (MAE). The predictions relied upon the experimental evaluation of the impedance of each surface at grazing angles of incidence. This evaluation was achieved by a fairly standard technique involving empirical models of various generic types of surfaces. An example was shown of the important role that the structural intricacies of a surface play in the determination of an appropriate model. The comparison between the measurements and predictions clearly indicated that the theory gives an excellent description of the field anywhere near a curved surface. The theory was also shown to give nearly as good of a description of the field surrounding a curved surface even at distances far behind the surface yet near the line of sight.

  5. A Investigation of the Diffraction of AN Acoustic Plane Wave by a Curved Surface of Finite Impedance.

    NASA Astrophysics Data System (ADS)

    Kearns, James Andrew

    Phenomena associated with long range propagation of sound over irregular topography motivated the research work which was described in this thesis. Specifically,the goal of the work was to analyze the diffraction effects which would occur near the tops of hills and ridges. From this particular goal, the research work evolved into a study of the diffraction of a high frequency plane wave due to its grazing of a two-dimensional curved surface of finite impedance. Laboratory scale models were constructed and measurements were made of the field on, above, and behind either of two curved surfaces possessing distinctly different impedances; that is, one was soft while the other was hard. The experimental technique consisted of simultaneously measuring the pressure at a reference point and at a field point due to a transient pulse generated by an electric spark. The pressure waveforms were digitized and processed. As described in the thesis, the ratio of the discrete Fourier transforms of the two waveforms provided an estimate of the insertion loss between them. The results of the measurements were compared with the predictions of a theory which was derived by Pierce using the method of Matched Asymptotic Expansions (MAE). The predictions relied upon the experimental evaluation of the impedance of each surface at grazing angles of incidence. This evaluation was achieved by a fairly standard technique involving empirical models of various generic types of surfaces. An example was shown of the important role that the structural intricacies of a surface play in the determination of an appropriate model. The comparison between the measurements and predictions clearly indicated that the theory gives an excellent description of the field anywhere near a curved surface. Further, with a simple modification, the theory was also shown to give nearly as good of a description of the field surrounding a curved surface even at distances far behind the surface yet near the line of sight.

  6. An investigation of the diffraction of an acoustic plane wave by a curved surface of finite impedance

    NASA Astrophysics Data System (ADS)

    Kearns, James A.

    1989-12-01

    Phenomena associated with long range propagation of sound over irregular topography motivated this work, which was to analyze the diffraction effects which would occur near the tops of hills and ridges. The diffraction of a high frequency plane wave due to its grazing of a two-dimensional curved surface of finite impedance was also studied. Laboratory scale models were constructed and measurements were made of the field on, above, and behind either of two curved surfaces possessing distinctly different impedances; that is, one was soft while the other was hard. The experimental technique consisted of simultaneously measuring the pressure at a reference point and at a field point due to a transient pulse generated by an electric spark. The pressure waveforms were digitized and processed. The ratio of the discrete Fourier transforms of the two waveforms provided an estimate of the insertion loss between them. The results of the measurements were compared with the predictions of a theory which was derived by Pierce using the method of Matched Asymptotic Expansions (MAE). The predictions relied upon the experimental evaluation of the impedance of each surface at grazing angles of incidence. This evaluation was achieved by a fairly standard technique involving empirical models of various generic types of surfaces. An example was shown of the important role that the structural intricacies of a surface play in the determination of an appropriate model. The comparison between the measurements and predictions indicated that the theory gives an excellent description of the field anywhere near a curved surface. Further, with a simple modification, the theory was also shown to give nearly as good of a description of the field surrounding a curved surface even at distances far behind the surface yet near the line of sight.

  7. Superactivation of quantum nonlocality.

    PubMed

    Palazuelos, Carlos

    2012-11-01

    In this Letter we show that quantum nonlocality can be superactivated. That is, one can obtain violations of Bell inequalities by tensorizing a local state with itself. In the second part of this work we study how large these violations can be. In particular, we show the existence of quantum states with very low Bell violation but such that five copies of them give very large violations. In fact, this gap can be made arbitrarily large by increasing the dimension of the states.

  8. Uncertainty-induced quantum nonlocality

    NASA Astrophysics Data System (ADS)

    Wu, Shao-xiong; Zhang, Jun; Yu, Chang-shui; Song, He-shan

    2014-01-01

    Based on the skew information, we present a quantity, uncertainty-induced quantum nonlocality (UIN) to measure the quantum correlation. It can be considered as the updated version of the original measurement-induced nonlocality (MIN) preserving the good computability but eliminating the non-contractivity problem. For 2×d-dimensional state, it is shown that UIN can be given by a closed form. In addition, we also investigate the maximal uncertainty-induced nonlocality.

  9. Nonlocal and quasilocal field theories

    NASA Astrophysics Data System (ADS)

    Tomboulis, E. T.

    2015-12-01

    We investigate nonlocal field theories, a subject that has attracted some renewed interest in connection with nonlocal gravity models. We study, in particular, scalar theories of interacting delocalized fields, the delocalization being specified by nonlocal integral kernels. We distinguish between strictly nonlocal and quasilocal (compact support) kernels and impose conditions on them to insure UV finiteness and unitarity of amplitudes. We study the classical initial value problem for the partial integro-differential equations of motion in detail. We give rigorous proofs of the existence but accompanying loss of uniqueness of solutions due to the presence of future, as well as past, "delays," a manifestation of acausality. In the quantum theory we derive a generalization of the Bogoliubov causality condition equation for amplitudes, which explicitly exhibits the corrections due to nonlocality. One finds that, remarkably, for quasilocal kernels all acausal effects are confined within the compact support regions. We briefly discuss the extension to other types of fields and prospects of such theories.

  10. Optimal measurements for nonlocal correlations

    NASA Astrophysics Data System (ADS)

    Schwarz, Sacha; Stefanov, André; Wolf, Stefan; Montina, Alberto

    2016-08-01

    A problem in quantum information theory is to find the experimental setup that maximizes the nonlocality of correlations with respect to some suitable measure such as the violation of Bell inequalities. There are however some complications with Bell inequalities. First and foremost it is unfeasible to determine the whole set of Bell inequalities already for a few measurements and thus unfeasible to find the experimental setup maximizing their violation. Second, the Bell violation suffers from an ambiguity stemming from the choice of the normalization of the Bell coefficients. An alternative measure of nonlocality with a direct information-theoretic interpretation is the minimal amount of classical communication required for simulating nonlocal correlations. In the case of many instances simulated in parallel, the minimal communication cost per instance is called nonlocal capacity, and its computation can be reduced to a convex-optimization problem. This quantity can be computed for a higher number of measurements and turns out to be useful for finding the optimal experimental setup. Focusing on the bipartite case, we present a simple method for maximizing the nonlocal capacity over a given configuration space and, in particular, over a set of possible measurements, yielding the corresponding optimal setup. Furthermore, we show that there is a functional relationship between Bell violation and nonlocal capacity. The method is illustrated with numerical tests and compared with the maximization of the violation of CGLMP-type Bell inequalities on the basis of entangled two-qubit as well as two-qutrit states. Remarkably, the anomaly of nonlocality displayed by qutrits turns out to be even stronger if the nonlocal capacity is employed as a measure of nonlocality.

  11. (1+2)-dimensional strongly nonlocal solitons

    SciTech Connect

    Ouyang Shigen; Guo Qi

    2007-11-15

    Approximate solutions of (1+2)-dimensional strongly nonlocal solitons (SNSs) are presented. It is shown that the power of a SNS in a nematic liquid crystal is in direct proportion to the second power of the degree of nonlocality, the power of a SNS in a nonlocal medium with a logarithmic nonlocal response is in inverse proportion to the second power of its beamwidth, and the power of a SNS in a nonlocal medium with an sth-power decay nonlocal response is in direct proportion to the (s+2)th power of the degree of nonlocality.

  12. Fourier transform of the multicenter product of 1s hydrogenic orbitals and Coulomb or Yukawa potentials and the analytically reduced form for subsequent integrals that include plane waves

    NASA Technical Reports Server (NTRS)

    Straton, Jack C.

    1989-01-01

    The Fourier transform of the multicenter product of N 1s hydrogenic orbitals and M Coulomb or Yukawa potentials is given as an (M+N-1)-dimensional Feynman integral with external momenta and shifted coordinates. This is accomplished through the introduction of an integral transformation, in addition to the standard Feynman transformation for the denominators of the momentum representation of the terms in the product, which moves the resulting denominator into an exponential. This allows the angular dependence of the denominator to be combined with the angular dependence in the plane waves.

  13. Achieving plane wave accuracy in linear-scaling density functional theory applied to periodic systems: A case study on crystalline silicon

    NASA Astrophysics Data System (ADS)

    Skylaris, Chris-Kriton; Haynes, Peter D.

    2007-10-01

    Linear-scaling methods for density functional theory promise to revolutionize the scope and scale of first-principles quantum mechanical calculations. Crystalline silicon has been the system of choice for exploratory tests of such methods in the literature, yet attempts at quantitative comparisons under linear-scaling conditions with traditional methods or experimental results have not been forthcoming. A detailed study using the ONETEP code is reported here, demonstrating for the first time that plane wave accuracy can be achieved in linear-scaling calculations on periodic systems.

  14. Free-space propagation of extreme NA polarized beams using the vector plane wave spectrum method and multi-gigabyte FFTsV

    NASA Astrophysics Data System (ADS)

    Greynolds, Alan W.

    2009-08-01

    Certain lasers can have initial waists only a wavelength or less in size. Therefore, collection optics with extreme numerical apertures (NA) approaching unity are required. Although the design of these macro-optics using geometrical ray-tracing is trivial, determining the exact vectorial field entering them is not. The theory and implementation of Fourier, or plane wave spectrum (PWS), based methods is presented for not only the far-field, but also the near and intermediate. A real-world example is given for which at one point a 12 gigabyte two-dimensional fast Fourier transform (FFT) is required and unexpected polarization effects are observed.

  15. Bounds for nonlocality distillation protocols

    SciTech Connect

    Forster, Manuel

    2011-06-15

    Nonlocality can be quantified by the violation of a Bell inequality. Since this violation may be amplified by local operations, an alternative measure has been proposed--distillable nonlocality. The alternative measure is difficult to calculate exactly due to the double exponential growth of the parameter space. In this paper, we give a way to bound the distillable nonlocality of a resource by the solutions to a related optimization problem. Our upper bounds are exponentially easier to compute than the exact value and are shown to be meaningful in general and tight in some cases.

  16. Turbulence transport with nonlocal interactions

    SciTech Connect

    Linn, R.R.; Clark, T.T.; Harlow, F.H.; Turner, L.

    1998-03-01

    This preliminary report describes a variety of issues in turbulence transport analysis with particular emphasis on closure procedures that are nonlocal in wave-number and/or physical space. Anomalous behavior of the transport equations for large scale parts of the turbulence spectrum are resolved by including the physical space nonlocal interactions. Direct and reverse cascade processes in wave-number space are given a much richer potential for realistic description by the nonlocal formulations. The discussion also describes issues, many still not resolved, regarding new classes of self-similar form functions.

  17. Nonlocality in homogeneous superfluid turbulence

    NASA Astrophysics Data System (ADS)

    Dix, O. M.; Zieve, R. J.

    2014-10-01

    Simulating superfluid turbulence using the localized induction approximation allows neighboring parallel vortices to proliferate. In many circumstances a turbulent tangle becomes unsustainable, degenerating into a series of parallel, noninteracting vortex lines. Calculating with the fully nonlocal Biot-Savart law prevents this difficulty but also increases computation time. Here we use a truncated Biot-Savart integral to investigate the effects of nonlocality on homogeneous turbulence. We find that including the nonlocal interaction up to roughly the spacing between nearest-neighbor vortex segments prevents the parallel alignment from developing, yielding an accurate model of homogeneous superfluid turbulence with less computation time.

  18. Nonlocality and communication complexity

    NASA Astrophysics Data System (ADS)

    Buhrman, Harry; Cleve, Richard; Massar, Serge; de Wolf, Ronald

    2010-01-01

    Quantum information processing is the emerging field that defines and realizes computing devices that make use of quantum mechanical principles such as the superposition principle, entanglement, and interference. Until recently the common notion of computing was based on classical mechanics and did not take into account all the possibilities that physically realizable computing devices offer in principle. The field gained momentum after Shor developed an efficient algorithm for factoring numbers, demonstrating the potential computing powers that quantum computing devices can unleash. In this review the information counterpart of computing is studied. It was realized early on by Holevo that quantum bits, the quantum mechanical counterpart of classical bits, cannot be used for efficient transformation of information in the sense that arbitrary k -bit messages cannot be compressed into messages of k-1 qubits. The abstract form of the distributed computing setting is called communication complexity. It studies the amount of information, in terms of bits or in our case qubits, that two spatially separated computing devices need to exchange in order to perform some computational task. Surprisingly, quantum mechanics can be used to obtain dramatic advantages for such tasks. The area of quantum communication complexity is reviewed and it is shown how it connects the foundational physics questions regarding nonlocality with those of communication complexity studied in theoretical computer science. The first examples exhibiting the advantage of the use of qubits in distributed information-processing tasks were based on nonlocality tests. However, by now the field has produced strong and interesting quantum protocols and algorithms of its own that demonstrate that entanglement, although it cannot be used to replace communication, can be used to reduce the communication exponentially. In turn, these new advances yield a new outlook on the foundations of physics and could even

  19. Nonlocal anomalous Hall effect

    NASA Astrophysics Data System (ADS)

    Zhang, Shulei; Vignale, Giovanni

    Anomalous Hall effect (AHE) is a distinctive transport property of ferromagnetic metals arising from spin orbit coupling (SOC) in concert with spontaneous spin polarization. Nonetheless, recent experiments have shown that the effect also appears in a nonmagnetic metal in contact with a magnetic insulator. The main puzzle lies in the apparent absence of spin polarized electrons in the non-magnetic metal. Here, we theoretically demonstrate that the scattering of electrons from a rough metal-insulator interface is generally spin-dependent, which results in mutual conversion between spin and charge currents flowing in the plane of the layer. It is the current-carrying spin polarized electrons and the spin Hall effect in the bulk of the metal layer that conspire to generate the AH current. This novel AHE differs from the conventional one only in the spatial separation of the SOC and the magnetization, so we name it as nonlocal AHE. In contrast to other previously proposed mechanisms (e.g., spin Hall AHE and magnetic proximity effect (MPE)), the nonlocal AHE appears on the first order of spin Hall angle and does not rely on the induced moments in the metal layer, which make it experimentally detectable by contrasting the AH current directions of two layered structures such as Pt/Cu/YIG and β -Ta/Cu/YIG (with a thin inserted Cu layer to eliminate the MPE). We predict that the directions of the AH currents in these two trilayers would be opposite since the spin Hall angles of Pt and β -Ta are of opposite signs. Work supported by NSF Grants DMR-1406568.

  20. Second-Order Møller-Plesset Perturbation Theory in the Condensed Phase: An Efficient and Massively Parallel Gaussian and Plane Waves Approach.

    PubMed

    Del Ben, Mauro; Hutter, Jürg; VandeVondele, Joost

    2012-11-13

    A novel algorithm, based on a hybrid Gaussian and plane waves (GPW) approach, is developed for the canonical second-order Møller-Plesset perturbation energy (MP2) of finite and extended systems. The key aspect of the method is that the electron repulsion integrals (ia|λσ) are computed by direct integration between the products of Gaussian basis functions λσ and the electrostatic potential arising from a given occupied-virtual pair density ia. The electrostatic potential is obtained in a plane waves basis set after solving the Poisson equation in Fourier space. In particular, for condensed phase systems, this scheme is highly efficient. Furthermore, our implementation has low memory requirements and displays excellent parallel scalability up to 100 000 processes. In this way, canonical MP2 calculations for condensed phase systems containing hundreds of atoms or more than 5000 basis functions can be performed within minutes, while systems up to 1000 atoms and 10 000 basis functions remain feasible. Solid LiH has been employed as a benchmark to study basis set and system size convergence. Lattice constants and cohesive energies of various molecular crystals have been studied with MP2 and double-hybrid functionals. PMID:26605583

  1. An efficient plane wave spectral analysis to predict the focal region fields of parabolic reflector antennas for small and wide angle scanning

    NASA Astrophysics Data System (ADS)

    Nagamune, Akio; Pathak, Prabhakar H.

    1990-11-01

    An efficient approach is described for calculating the field distribution in the focal region of an electrically large, symmetric or offset parabolic reflector antenna with an arbitrary rim contour, when the concave reflector surface is fully illuminated by an obliquely incident arbitrary electromagnetic plane wave. This solution is useful for synthesizing feed arrays in scanning multiple and contour beam reflector antennas via reciprocity. The dominant contribution to the focal-region fields is found by transforming the physical-optics integral over the reflector surface into a plane-wave spectral (PWS) integral. An important feature of the approach is that the spectrum (or the PWS integrand) is obtained in closed form containing relatively simple functions upon dividing the reflector surface into just a few sections that yield rectangular projected apertures. The PWS integral is evaluated rapidly via the fast Fourier transform (FFT) algorithm to furnish, in only a single computation, the field for every place in the focal plane (or any plane parallel to it) within the focal region for a given direction of the incident wave. The correction to the physical-optics field is relatively small in the focal region and may therefore be neglected. Numerical results based on this PWS approach are presented, and their accuracy is established by comparison with results based on other approaches.

  2. Nonlocal Anomalous Hall Effect

    NASA Astrophysics Data System (ADS)

    Zhang, Steven S.-L.; Vignale, Giovanni

    2016-04-01

    The anomalous Hall (AH) effect is deemed to be a unique transport property of ferromagnetic metals, caused by the concerted action of spin polarization and spin-orbit coupling. Nevertheless, recent experiments have shown that the effect also occurs in a nonmagnetic metal (Pt) in contact with a magnetic insulator [yttrium iron garnet (YIG)], even when precautions are taken to ensure that there is no induced magnetization in the metal. We propose a theory of this effect based on the combined action of spin-dependent scattering from the magnetic interface and the spin-Hall effect in the bulk of the metal. At variance with previous theories, we predict the effect to be of first order in the spin-orbit coupling, just as the conventional anomalous Hall effect—the only difference being the spatial separation of the spin-orbit interaction and the magnetization. For this reason we name this effect the nonlocal anomalous Hall effect and predict that its sign will be determined by the sign of the spin-Hall angle in the metal. The AH conductivity that we calculate from our theory is in order of magnitude agreement with the measured values in Pt /YIG structures.

  3. Bipartite units of nonlocality

    SciTech Connect

    Forster, Manuel; Wolf, Stefan

    2011-10-15

    Imagine a task in which a group of separated players aim to simulate a statistic that violates a Bell inequality. Given measurement choices the players shall announce an output based solely on the results of local operations--which they can discuss before the separation--on shared random data and shared copies of a so-called unit correlation. In the first part of this paper we show that in such a setting the simulation of any bipartite correlation, not containing the possibility of signaling, can be made arbitrarily accurate by increasing the number of shared Popescu-Rohrlich (PR) boxes. This establishes the PR box as a simple asymptotic unit of bipartite nonlocality. In the second part we study whether this property extends to the multipartite case. More generally, we ask if it is possible for separated players to asymptotically reproduce any nonsignaling statistic by local operations on bipartite unit correlations. We find that nonadaptive strategies are limited by a constant accuracy and that arbitrary strategies on n resource correlations make a mistake with a probability greater or equal to c/n, for some constant c.

  4. Fast separable nonlocal means

    NASA Astrophysics Data System (ADS)

    Ghosh, Sanjay; Chaudhury, Kunal N.

    2016-03-01

    We propose a simple and fast algorithm called PatchLift for computing distances between patches (contiguous block of samples) extracted from a given one-dimensional signal. PatchLift is based on the observation that the patch distances can be efficiently computed from a matrix that is derived from the one-dimensional signal using lifting; importantly, the number of operations required to compute the patch distances using this approach does not scale with the patch length. We next demonstrate how PatchLift can be used for patch-based denoising of images corrupted with Gaussian noise. In particular, we propose a separable formulation of the classical nonlocal means (NLM) algorithm that can be implemented using PatchLift. We demonstrate that the PatchLift-based implementation of separable NLM is a few orders faster than standard NLM and is competitive with existing fast implementations of NLM. Moreover, its denoising performance is shown to be consistently superior to that of NLM and some of its variants, both in terms of peak signal-to-noise ratio/structural similarity index and visual quality.

  5. Nonlocal Intracranial Cavity Extraction

    PubMed Central

    Manjón, José V.; Eskildsen, Simon F.; Coupé, Pierrick; Romero, José E.; Collins, D. Louis; Robles, Montserrat

    2014-01-01

    Automatic and accurate methods to estimate normalized regional brain volumes from MRI data are valuable tools which may help to obtain an objective diagnosis and followup of many neurological diseases. To estimate such regional brain volumes, the intracranial cavity volume (ICV) is often used for normalization. However, the high variability of brain shape and size due to normal intersubject variability, normal changes occurring over the lifespan, and abnormal changes due to disease makes the ICV estimation problem challenging. In this paper, we present a new approach to perform ICV extraction based on the use of a library of prelabeled brain images to capture the large variability of brain shapes. To this end, an improved nonlocal label fusion scheme based on BEaST technique is proposed to increase the accuracy of the ICV estimation. The proposed method is compared with recent state-of-the-art methods and the results demonstrate an improved performance both in terms of accuracy and reproducibility while maintaining a reduced computational burden. PMID:25328511

  6. Nonlocal intracranial cavity extraction.

    PubMed

    Manjón, José V; Eskildsen, Simon F; Coupé, Pierrick; Romero, José E; Collins, D Louis; Robles, Montserrat

    2014-01-01

    Automatic and accurate methods to estimate normalized regional brain volumes from MRI data are valuable tools which may help to obtain an objective diagnosis and followup of many neurological diseases. To estimate such regional brain volumes, the intracranial cavity volume (ICV) is often used for normalization. However, the high variability of brain shape and size due to normal intersubject variability, normal changes occurring over the lifespan, and abnormal changes due to disease makes the ICV estimation problem challenging. In this paper, we present a new approach to perform ICV extraction based on the use of a library of prelabeled brain images to capture the large variability of brain shapes. To this end, an improved nonlocal label fusion scheme based on BEaST technique is proposed to increase the accuracy of the ICV estimation. The proposed method is compared with recent state-of-the-art methods and the results demonstrate an improved performance both in terms of accuracy and reproducibility while maintaining a reduced computational burden. PMID:25328511

  7. Nonlocal Anomalous Hall Effect.

    PubMed

    Zhang, Steven S-L; Vignale, Giovanni

    2016-04-01

    The anomalous Hall (AH) effect is deemed to be a unique transport property of ferromagnetic metals, caused by the concerted action of spin polarization and spin-orbit coupling. Nevertheless, recent experiments have shown that the effect also occurs in a nonmagnetic metal (Pt) in contact with a magnetic insulator [yttrium iron garnet (YIG)], even when precautions are taken to ensure that there is no induced magnetization in the metal. We propose a theory of this effect based on the combined action of spin-dependent scattering from the magnetic interface and the spin-Hall effect in the bulk of the metal. At variance with previous theories, we predict the effect to be of first order in the spin-orbit coupling, just as the conventional anomalous Hall effect-the only difference being the spatial separation of the spin-orbit interaction and the magnetization. For this reason we name this effect the nonlocal anomalous Hall effect and predict that its sign will be determined by the sign of the spin-Hall angle in the metal. The AH conductivity that we calculate from our theory is in order of magnitude agreement with the measured values in Pt/YIG structures.

  8. The t-matrix resistivity of liquid rare earth metals using pseudopotential

    SciTech Connect

    Bhatia, Kamaldeep G.; Bhatt, N. K.; Vyas, P. R.; Gohel, V. B.

    2015-06-24

    Present theoretical study of liquid metal resistivity of some trivalent (La,Ce,Gd) and divalent (Eu,Yb) rare earth metals using pseudopotential has been carried out employing Ziman’s weak scattering and transition matrix (t-matrix) approaches. Our computed results of liquid metal resistivity using t-matrix approach are better than resistivity computed using Ziman’s approach and are also in excellent agreement with experimental results and other theoretical findings. The present study confirms that for f-shell metals pseudopotential must be determined uniquely and t-matrix approach is more physical in comparison with Ziman’s nearly free electron approach. The present pseudopotential accounts s-p-d hybridization properly. Such success encourages us to study remaining liquid state properties of these metals.

  9. Lattice Boltzmann modeling of multiphase flows at large density ratio with an improved pseudopotential model.

    PubMed

    Li, Q; Luo, K H; Li, X J

    2013-05-01

    Owing to its conceptual simplicity and computational efficiency, the pseudopotential multiphase lattice Boltzmann (LB) model has attracted significant attention since its emergence. In this work, we aim to extend the pseudopotential LB model to simulate multiphase flows at large density ratio and relatively high Reynolds number. First, based on our recent work [Q. Li, K. H. Luo, and X. J. Li, Phys. Rev. E 86, 016709 (2012)], an improved forcing scheme is proposed for the multiple-relaxation-time pseudopotential LB model in order to achieve thermodynamic consistency and large density ratio in the model. Next, through investigating the effects of the parameter a in the Carnahan-Starling equation of state, we find that the interface thickness is approximately proportional to 1/√a. Using a smaller a will lead to a wider interface thickness, which can reduce the spurious currents and enhance the numerical stability of the pseudopotential model at large density ratio. Furthermore, it is found that a lower liquid viscosity can be gained in the pseudopotential model by increasing the kinematic viscosity ratio between the vapor and liquid phases. The improved pseudopotential LB model is numerically validated via the simulations of stationary droplet and droplet oscillation. Using the improved model as well as the above treatments, numerical simulations of droplet splashing on a thin liquid film are conducted at a density ratio in excess of 500 with Reynolds numbers ranging from 40 to 1000. The dynamics of droplet splashing is correctly reproduced and the predicted spread radius is found to obey the power law reported in the literature. PMID:23767651

  10. Nonlocal Measurements via Quantum Erasure.

    PubMed

    Brodutch, Aharon; Cohen, Eliahu

    2016-02-19

    Nonlocal observables play an important role in quantum theory, from Bell inequalities and various postselection paradoxes to quantum error correction codes. Instantaneous measurement of these observables is known to be a difficult problem, especially when the measurements are projective. The standard von Neumann Hamiltonian used to model projective measurements cannot be implemented directly in a nonlocal scenario and can, in some cases, violate causality. We present a scheme for effectively generating the von Neumann Hamiltonian for nonlocal observables without the need to communicate and adapt. The protocol can be used to perform weak and strong (projective) measurements, as well as measurements at any intermediate strength. It can also be used in practical situations beyond nonlocal measurements. We show how the protocol can be used to probe a version of Hardy's paradox with both weak and strong measurements. The outcomes of these measurements provide a nonintuitive picture of the pre- and postselected system. Our results shed new light on the interplay between quantum measurements, uncertainty, nonlocality, causality, and determinism. PMID:26943514

  11. Resonance reflection of elastic waves at the interface between two crystals with sliding contact: II. Plane waves and acoustic beams in structures with hexagonal symmetry

    SciTech Connect

    Alshits, V.I.; Darinskii, A.N.; Radovich, A.

    1995-05-01

    The specific features of acoustic wave reflection are analyzed at the interface between two hexagonal crystals with a sliding contact between them. Attention is focused on the angles of incidence corresponding to excitation of the leaky wave. The conditions supporting the existence of leaky waves are found. The expressions illustrating the behavior of plane wave transformation coefficients for reflection, refraction, and excitation of interfacial oscillations are found in analytic form. In addition, the features of nonmirror reflection are studied for a slightly diverging acoustic beam having initially a rectangular profile. The study deals with the case when the tangential projection of the {open_quotes}mean{close_quotes} wavevector for the beam is close to or coincides with the real part of the wavevector of the leaky wave. 9 refs., 10 figs.

  12. Optimal one-section and two-section circular sound-absorbing duct liners for plane-wave and monopole sources without flow

    NASA Technical Reports Server (NTRS)

    Lester, H. C.; Posey, J. W.

    1976-01-01

    A discrete frequency study is made of the influence of source characteristics on the optimal properties of acoustically lined uniform and two section ducts. Two simplified sources, a plane wave and a monopole, are considered in some detail and over a greater frequency range than has been previously studied. Source and termination impedance effects are given limited examination. An example of a turbomachinery source and three associated source variants is also presented. Optimal liner designs based on modal theory approach the Cremer criterion at low frequencies and the geometric acoustics limit at high frequencies. Over an intermediate frequency range, optimal two section liners produced higher transmission losses than did the uniform configurations. Source distribution effects were found to have a significant effect on optimal liner design, but source and termination impedance effects appear to be relatively unimportant.

  13. On the calculation of the complex wavenumber of plane waves in rigid-walled low-Mach-number turbulent pipe flows

    NASA Astrophysics Data System (ADS)

    Weng, Chenyang; Boij, Susann; Hanifi, Ardeshir

    2015-10-01

    A numerical method for calculating the wavenumbers of axisymmetric plane waves in rigid-walled low-Mach-number turbulent flows is proposed, which is based on solving the linearized Navier-Stokes equations with an eddy-viscosity model. In addition, theoretical models for the wavenumbers are reviewed, and the main effects (the viscothermal effects, the mean flow convection and refraction effects, the turbulent absorption, and the moderate compressibility effects) which may influence the sound propagation are discussed. Compared to the theoretical models, the proposed numerical method has the advantage of potentially including more effects in the computed wavenumbers. The numerical results of the wavenumbers are compared with the reviewed theoretical models, as well as experimental data from the literature. It shows that the proposed numerical method can give satisfactory prediction of both the real part (phase shift) and the imaginary part (attenuation) of the measured wavenumbers, especially when the refraction effects or the turbulent absorption effects become important.

  14. Extended application of Kohn-Sham first-principles molecular dynamics method with plane wave approximation at high energy—From cold materials to hot dense plasmas

    NASA Astrophysics Data System (ADS)

    Zhang, Shen; Wang, Hongwei; Kang, Wei; Zhang, Ping; He, X. T.

    2016-04-01

    An extended first-principles molecular dynamics (FPMD) method based on Kohn-Sham scheme is proposed to elevate the temperature limit of the FPMD method in the calculation of dense plasmas. The extended method treats the wave functions of high energy electrons as plane waves analytically and thus expands the application of the FPMD method to the region of hot dense plasmas without suffering from the formidable computational costs. In addition, the extended method inherits the high accuracy of the Kohn-Sham scheme and keeps the information of electronic structures. This gives an edge to the extended method in the calculation of mixtures of plasmas composed of heterogeneous ions, high-Z dense plasmas, lowering of ionization potentials, X-ray absorption/emission spectra, and opacities, which are of particular interest to astrophysics, inertial confinement fusion engineering, and laboratory astrophysics.

  15. Polymorphism of resorcinol explored by complementary vibrational spectroscopy (FT-RS, THz-TDS, INS) and first-principles solid-state computations (plane-wave DFT).

    PubMed

    Drużbicki, Kacper; Mikuli, Edward; Pałka, Norbert; Zalewski, Sławomir; Ossowska-Chruściel, Mirosława D

    2015-01-29

    The polymorphism of resorcinol has been complementary studied by combining Raman, time-domain terahertz, and inelastic neutron scattering spectroscopy with modern solid-state density functional theory (DFT) calculations. The spectral differences, emerging from the temperature-induced structural phase transition, have been successfully interpreted with an emphasis on the low-wavenumber range. The given interpretation is based on the plane-wave DFT computations, providing an excellent overall reproduction of both wavenumbers and intensities and revealing the source of the observed spectral differences. The performance of the generalized gradient approximation (GGA) functionals in prediction of the structural parameters and the vibrational spectra of the normal-pressure polymorphs of resorcinol has been extensively examined. The results show that the standard Perdew, Burke, and Ernzerhof (PBE) approach along with its "hard" revised form tends to be superior if compared to the "soft" GGA approximation.

  16. Polymorphism of resorcinol explored by complementary vibrational spectroscopy (FT-RS, THz-TDS, INS) and first-principles solid-state computations (plane-wave DFT).

    PubMed

    Drużbicki, Kacper; Mikuli, Edward; Pałka, Norbert; Zalewski, Sławomir; Ossowska-Chruściel, Mirosława D

    2015-01-29

    The polymorphism of resorcinol has been complementary studied by combining Raman, time-domain terahertz, and inelastic neutron scattering spectroscopy with modern solid-state density functional theory (DFT) calculations. The spectral differences, emerging from the temperature-induced structural phase transition, have been successfully interpreted with an emphasis on the low-wavenumber range. The given interpretation is based on the plane-wave DFT computations, providing an excellent overall reproduction of both wavenumbers and intensities and revealing the source of the observed spectral differences. The performance of the generalized gradient approximation (GGA) functionals in prediction of the structural parameters and the vibrational spectra of the normal-pressure polymorphs of resorcinol has been extensively examined. The results show that the standard Perdew, Burke, and Ernzerhof (PBE) approach along with its "hard" revised form tends to be superior if compared to the "soft" GGA approximation. PMID:25564699

  17. Acoustic plane waves normally incident on a clamped panel in a rectangular duct. [to explain noise reduction curves for reducing interior noise in aircraft

    NASA Technical Reports Server (NTRS)

    Unz, H.; Roskam, J.

    1979-01-01

    The theory of acoustic plane wave normally incident on a clamped panel in a rectangular duct is developed. The coupling theory between the elastic vibrations of the panel (plate) and the acoustic wave propagation in infinite space and in the rectangular duct is considered. The partial differential equation which governs the vibration of the panel (plate) is modified by adding to its stiffness (spring) forces and damping forces, and the fundamental resonance frequency and the attenuation factor are discussed. The noise reduction expression based on the theory is found to agree well with the corresponding experimental data of a sample aluminum panel in the mass controlled region, the damping controlled region, and the stiffness controlled region. All the frequency positions of the upward and downward resonance spikes in the sample experimental data are identified theoretically as resulting from four cross interacting major resonance phenomena: the cavity resonance, the acoustic resonance, the plate resonance, and the wooden back panel resonance.

  18. Numerical study on surface plasmon polariton behaviors in periodic metal-dielectric structures using a plane-wave-assisted boundary integral-equation method.

    PubMed

    Kiang, Yean-Woei; Wang, Jyh-Yang; Yang, C C

    2007-07-01

    A novel hybrid technique based on the boundary integral-equation method is proposed for studying the surface plasmon polariton behaviors in two-dimensional periodic structures. Considering the periodicity property of the problem, we use the plane-wave expansion concept and the periodic boundary condition instead of using the periodic Green's function. The diffraction efficiency can then be readily calculated once the equivalent electric and magnetic currents are solved that avoids invoking the numerical calculation of the radiation integral. The numerical validity is verified with the cases of highly conducting materials and practical metals. Numerical convergence can be easily achieved even in the case of a large incident angle as 80o. Based on the numerical scheme, a metal-dielectric wavy structure is designed for enhancing the transmittance of optical signal through the structure. The excitation of the coupled surface plasmon polaritons for the high transmission is demonstrated.

  19. Applying a modified plane-wave expansion method to the calculations of transmittivity and reflectivity of a semi-infinite photonic crystal.

    PubMed

    Hsue, Young-Chung; Yang, Tzong-Jer

    2004-01-01

    We propose a modified plane-wave expansion method to calculate transmittivity and reflectivity of a semi-infinite photonic crystal (PC) with interface. This method is based on an expanded completeness basis, including both the propagation and evanescence modes. We use this approach to deal with two kinds of problems: one is to determine the normal direction of the largest attenuation strength for a semi-infinite PC in the gap frequencies; the other is to calculate the transmittivity and reflectivity of a PC slab. To demonstrate the extensive utilization of our approach, we revisit the same system as studied by Phys. Rev. B 52, 8992 (1995)] and find that our results are in good agreement with ones obtained by Sakoda's paper.

  20. Split-step-type angular plane-wave spectrum method for the study of self-refractive effects in nonlinear wave propagation

    NASA Astrophysics Data System (ADS)

    Korpel, A.; Lonngren, K. E.; Banerjee, P. P.; Sim, H. K.; Chatterjee, M. R.

    1986-06-01

    A novel algorithm is reported that simulates the effect of a cubic nonlinearity on wave propagation by combining angular plane-wave spectrum techniques in the Fourier domain with self-induced thin lens techniques in the space domain. The amplitude-dependent propagation constant is briefly derived from the scalar wave equation with cubic nonlinearity. The angular spectrum method is used to derive an expression for the emerging wave in the presence of cubic nonlinearity, including the nonlinearly induced thin lens effect. The propagation of a Gaussian beam and the diffraction from a rectangular aperture are calculated to check the algorithm, and the nonlinear evolution of these cases is presented. Finally, the existence of a particular analytic steady state solution is demonstrated and tested using the algorithm.

  1. A high frequency analysis of electromagnetic plane wave scattering by perfectly-conducting semi-infinite parallel plate and rectangular waveguides with absorber coated inner walls

    NASA Technical Reports Server (NTRS)

    Noh, H. M.; Pathak, P. H.

    1986-01-01

    An approximate but sufficiently accurate high frequency solution which combines the uniform geometrical theory of diffraction (UTD) and the aperture integration (AI) method is developed for analyzing the problem of electromagnetic (EM) plane wave scattering by an open-ended, perfectly-conducting, semi-infinite hollow rectangular waveguide (or duct) with a thin, uniform layer of lossy or absorbing material on its inner wall, and with a planar termination inside. In addition, a high frequency solution for the EM scattering by a two dimensional (2-D), semi-infinite parallel plate waveguide with a absorber coating on the inner walls is also developed as a first step before analyzing the open-ended semi-infinite three dimensional (3-D) rectangular waveguide geometry. The total field scattered by the semi-infinite waveguide consists firstly of the fields scattered from the edges of the aperture at the open-end, and secondly of the fields which are coupled into the waveguide from the open-end and then reflected back from the interior termination to radiate out of the open-end. The first contribution to the scattered field can be found directly via the UTD ray method. The second contribution is found via the AI method which employs rays to describe the fields in the aperture that arrive there after reflecting from the interior termination. It is assumed that the direction of the incident plane wave and the direction of observation lie well inside the forward half space tht exists outside the half space containing the semi-infinite waveguide geometry. Also, the medium exterior to the waveguide is assumed to be free space.

  2. Norm-conserving pseudopotentials with chemical accuracy compared to all-electron calculations

    NASA Astrophysics Data System (ADS)

    Willand, Alex; Kvashnin, Yaroslav O.; Genovese, Luigi; Vázquez-Mayagoitia, Álvaro; Deb, Arpan Krishna; Sadeghi, Ali; Deutsch, Thierry; Goedecker, Stefan

    2013-03-01

    By adding a nonlinear core correction to the well established dual space Gaussian type pseudopotentials for the chemical elements up to the third period, we construct improved pseudopotentials for the Perdew-Burke-Ernzerhof [J. Perdew, K. Burke, and M. Ernzerhof, Phys. Rev. Lett. 77, 3865 (1996), 10.1103/PhysRevLett.77.3865] functional and demonstrate that they exhibit excellent accuracy. Our benchmarks for the G2-1 test set show average atomization energy errors of only half a kcal/mol. The pseudopotentials also remain highly reliable for high pressure phases of crystalline solids. When supplemented by empirical dispersion corrections [S. Grimme, J. Comput. Chem. 27, 1787 (2006), 10.1002/jcc.20495; S. Grimme, J. Antony, S. Ehrlich, and H. Krieg, J. Chem. Phys. 132, 154104 (2010), 10.1063/1.3382344] the average error in the interaction energy between molecules is also about half a kcal/mol. The accuracy that can be obtained by these pseudopotentials in combination with a systematic basis set is well superior to the accuracy that can be obtained by commonly used medium size Gaussian basis sets in all-electron calculations.

  3. Achieving tunable surface tension in the pseudopotential lattice Boltzmann modeling of multiphase flows.

    PubMed

    Li, Qing; Luo, K H

    2013-11-01

    In this paper, we aim to address an important issue about the pseudopotential lattice Boltzmann (LB) model, which has attracted much attention as a mesoscopic model for simulating interfacial dynamics of complex fluids, but suffers from the problem that the surface tension cannot be tuned independently of the density ratio. In the literature, a multirange potential was devised to adjust the surface tension [Sbragaglia et al., Phys. Rev. E 75, 026702 (2007)]. However, it was recently found that the density ratio of the system will be changed when the multirange potential is employed to adjust the surface tension. An alternative approach is therefore proposed in the present work. The basic strategy is to add a source term to the LB equation so as to tune the surface tension of the pseudopotential LB model. The proposed approach can guarantee that the adjustment of the surface tension does not affect the mechanical stability condition of the pseudopotential LB model, and thus provides a separate control of the surface tension and the density ratio. Meanwhile, it still retains the mesoscopic feature and the computational simplicity of the pseudopotential LB model. Numerical simulations are carried out for stationary droplets, capillary waves, and droplet splashing on a thin liquid film. The numerical results demonstrate that the proposed approach is capable of achieving a tunable surface tension over a very wide range and can keep the density ratio unchanged when adjusting the surface tension.

  4. Achieving tunable surface tension in the pseudopotential lattice Boltzmann modeling of multiphase flows.

    PubMed

    Li, Qing; Luo, K H

    2013-11-01

    In this paper, we aim to address an important issue about the pseudopotential lattice Boltzmann (LB) model, which has attracted much attention as a mesoscopic model for simulating interfacial dynamics of complex fluids, but suffers from the problem that the surface tension cannot be tuned independently of the density ratio. In the literature, a multirange potential was devised to adjust the surface tension [Sbragaglia et al., Phys. Rev. E 75, 026702 (2007)]. However, it was recently found that the density ratio of the system will be changed when the multirange potential is employed to adjust the surface tension. An alternative approach is therefore proposed in the present work. The basic strategy is to add a source term to the LB equation so as to tune the surface tension of the pseudopotential LB model. The proposed approach can guarantee that the adjustment of the surface tension does not affect the mechanical stability condition of the pseudopotential LB model, and thus provides a separate control of the surface tension and the density ratio. Meanwhile, it still retains the mesoscopic feature and the computational simplicity of the pseudopotential LB model. Numerical simulations are carried out for stationary droplets, capillary waves, and droplet splashing on a thin liquid film. The numerical results demonstrate that the proposed approach is capable of achieving a tunable surface tension over a very wide range and can keep the density ratio unchanged when adjusting the surface tension. PMID:24329379

  5. Nonlocal orbital-free density functional theory for warm dense matter

    NASA Astrophysics Data System (ADS)

    Sjostrom, Travis

    2014-03-01

    Accurate simulations of warm dense matter remain challenging in current research, while being motivated further as recent experiments probe more accurately into this regime. While the de facto standard is quantum molecular dynamics using Kohn-Sham DFT, this methods scales significantly with temperature due to the orbital dependence. From the other side, the orbital-free Thomas-Fermi approximation works well for hot dense systems, but loses accuracy at lower temperatures. Recently developed nonlocal orbital-free functionals for the noninteracting free energy [Phys. Rev. B 88, 195103], which show near Kohn-Sham accuracy for broad ranges of temperature and density are presented. The application of which are detailed in regards to pseudopotentials and molecular dynamics for various systems. Comparisons with local orbital-free methods as well as orbital-dependent Kohn-Sham calculations, including accuracy and computational cost are made. This research has been supported by the DOE Office of Fusion Sciences (FES).

  6. Nonlocal energy-optimized kernel: Recovering second-order exchange in the homogeneous electron gas

    NASA Astrophysics Data System (ADS)

    Bates, Jefferson E.; Laricchia, Savio; Ruzsinszky, Adrienn

    2016-01-01

    In order to remedy some of the shortcomings of the random phase approximation (RPA) within adiabatic connection fluctuation-dissipation (ACFD) density functional theory, we introduce a short-ranged, exchange-like kernel that is one-electron self-correlation free and exact for two-electron systems in the high-density limit. By tuning a free parameter in our model to recover an exact limit of the homogeneous electron gas correlation energy, we obtain a nonlocal, energy-optimized kernel that reduces the errors of RPA for both homogeneous and inhomogeneous solids. Using wave-vector symmetrization for the kernel, we also implement RPA renormalized perturbation theory for extended systems, and demonstrate its capability to describe the dominant correlation effects with a low-order expansion in both metallic and nonmetallic systems. The comparison of ACFD structural properties with experiment is also shown to be limited by the choice of norm-conserving pseudopotential.

  7. Quantum nonlocality does not exist.

    PubMed

    Tipler, Frank J

    2014-08-01

    Quantum nonlocality is shown to be an artifact of the Copenhagen interpretation, in which each observed quantity has exactly one value at any instant. In reality, all physical systems obey quantum mechanics, which obeys no such rule. Locality is restored if observed and observer are both assumed to obey quantum mechanics, as in the many-worlds interpretation (MWI). Using the MWI, I show that the quantum side of Bell's inequality, generally believed nonlocal, is really due to a series of three measurements (not two as in the standard, oversimplified analysis), all three of which have only local effects. Thus, experiments confirming "nonlocality" are actually confirming the MWI. The mistaken interpretation of nonlocality experiments depends crucially on a question-begging version of the Born interpretation, which makes sense only in "collapse" versions of quantum theory, about the meaning of the modulus of the wave function, so I use the interpretation based on the MWI, namely that the wave function is a world density amplitude, not a probability amplitude. This view allows the Born interpretation to be derived directly from the Schrödinger equation, by applying the Schrödinger equation to both the observed and the observer.

  8. Learning Non-Local Dependencies

    ERIC Educational Resources Information Center

    Kuhn, Gustav; Dienes, Zoltan

    2008-01-01

    This paper addresses the nature of the temporary storage buffer used in implicit or statistical learning. Kuhn and Dienes [Kuhn, G., & Dienes, Z. (2005). Implicit learning of nonlocal musical rules: implicitly learning more than chunks. "Journal of Experimental Psychology-Learning Memory and Cognition," 31(6) 1417-1432] showed that people could…

  9. On nonlocal electron heat conduction

    SciTech Connect

    Krasheninnikov, S.I. )

    1993-01-01

    An improvement of the Albritton nonlocal electron heat transport model is proposed for high-[ital Z] plasmas. The thermal decay of the temperature perturbation in a uniform plasma as calculated by this model is compared with that obtained by Fokker--Planck simulations. Complete agreement is found up to values [ital k][lambda][sub [ital e

  10. Nonlocal Equations with Measure Data

    NASA Astrophysics Data System (ADS)

    Kuusi, Tuomo; Mingione, Giuseppe; Sire, Yannick

    2015-08-01

    We develop an existence, regularity and potential theory for nonlinear integrodifferential equations involving measure data. The nonlocal elliptic operators considered are possibly degenerate and cover the case of the fractional p-Laplacean operator with measurable coefficients. We introduce a natural function class where we solve the Dirichlet problem, and prove basic and optimal nonlinear Wolff potential estimates for solutions. These are the exact analogs of the results valid in the case of local quasilinear degenerate equations established by Boccardo and Gallouët (J Funct Anal 87:149-169, 1989, Partial Differ Equ 17:641-655, 1992) and Kilpeläinen and Malý (Ann Scuola Norm Sup Pisa Cl Sci (IV) 19:591-613, 1992, Acta Math 172:137-161, 1994). As a consequence, we establish a number of results that can be considered as basic building blocks for a nonlocal, nonlinear potential theory: fine properties of solutions, Calderón-Zygmund estimates, continuity and boundedness criteria are established via Wolff potentials. A main tool is the introduction of a global excess functional that allows us to prove a nonlocal analog of the classical theory due to Campanato (Ann Mat Pura Appl (IV) 69:321-381, 1965). Our results cover the case of linear nonlocal equations with measurable coefficients, and the one of the fractional Laplacean, and are new already in such cases.

  11. Quantum nonlocality does not exist.

    PubMed

    Tipler, Frank J

    2014-08-01

    Quantum nonlocality is shown to be an artifact of the Copenhagen interpretation, in which each observed quantity has exactly one value at any instant. In reality, all physical systems obey quantum mechanics, which obeys no such rule. Locality is restored if observed and observer are both assumed to obey quantum mechanics, as in the many-worlds interpretation (MWI). Using the MWI, I show that the quantum side of Bell's inequality, generally believed nonlocal, is really due to a series of three measurements (not two as in the standard, oversimplified analysis), all three of which have only local effects. Thus, experiments confirming "nonlocality" are actually confirming the MWI. The mistaken interpretation of nonlocality experiments depends crucially on a question-begging version of the Born interpretation, which makes sense only in "collapse" versions of quantum theory, about the meaning of the modulus of the wave function, so I use the interpretation based on the MWI, namely that the wave function is a world density amplitude, not a probability amplitude. This view allows the Born interpretation to be derived directly from the Schrödinger equation, by applying the Schrödinger equation to both the observed and the observer. PMID:25015084

  12. Averaging Horizontal-to-Vertical (H/V) Spectral Ratios of Earthquake Motions for Velocity Inversions Based on Diffuse Field Theory for Plane Waves

    NASA Astrophysics Data System (ADS)

    Matsushima, S.; Sanchez-Sesma, F. J.; Kawase, H.

    2010-12-01

    In this work we explore the application of diffuse field concepts to analyze strong motion records at a site in which site effects can be described using a one dimensional (1D) model. For this case we derived a corollary of Claerbout (1968) result for 1D layered medium. We found that the imaginary part of Green function at the free surface is proportional to the square of the absolute value of the corresponding transfer function for a plane, vertically incident wave with unit amplitude. Average strong ground motion in a "sufficiently" flat layered site will be statistically equivalent. We may conceive the illumination as produced by incident plane waves. They represent the most important part of earthquake ground motions. Their associated motions, being multiple scattered, are formed of waves that sample significant portions of the considered area. This is a distinctive feature of earthquake motions, for which the excited domain is large, basically from the source to the receiver. For a set of incoming plane waves (of P, SV, and SH types) with varying azimuths and incidence angles we assume that the ground motion will be spatially homogeneous in a statistical sense. In other words, the average of normalized ground motion spectral densities will depend only on depth. Therefore, we can apply a 1D description of wave propagation for a diffuse (average) field of ground motions. To prove the above hypothesis for H/V ratios of earthquake ground motions, we first show a comparison of averaged synthetics of 1D underground structures with a corresponding simple theoretical prediction from 1D transfer functions. After summing up a few hundreds of synthetics with different angles of incidences, azimuths, and polarizations, we can obtain identical H/V ratios that the simple theory of diffuse field predicts. Then we show several examples of H/V ratios for actual seismic motions observed in Japan. We found that the earthquake H/V ratios are quite stable (and converging rapidly

  13. Shear-deformation-potential constant of the conduction-band minima of Si: Pseudopotential calculations

    NASA Astrophysics Data System (ADS)

    Li, Ming-Fu; Gu, Zong-Quan; Wang, Jian-Qing

    1990-09-01

    We have calculated the value of the shear-deformation-potential constant Ξu of the conduction-band minima of Si and its temperature coefficient dΞu/dT. The value of Ξu is 9.0 eV for an ab initio pseudopotential calculation and 10.8 eV by the empirical-pseudopotential method (EPM), in good agreement with our experiment. The EPM calculations of the temperature dependence of Ξu yield the values of (dΞu/dT)||DW=-0.04 meV/K due to the Debye-Waller contribution, and (dΞu/dT)||TE=-0.04 meV/K for thermal expansion. We suspect and suggest that the existing experimental value of dΞu/dT~=+3 meV/K is unreliable due to large experimental uncertainty.

  14. Randomness versus Nonlocality and Entanglement

    NASA Astrophysics Data System (ADS)

    Acín, Antonio; Massar, Serge; Pironio, Stefano

    2012-03-01

    The outcomes obtained in Bell tests involving two-outcome measurements on two subsystems can, in principle, generate up to 2 bits of randomness. However, the maximal violation of the Clauser-Horne-Shimony-Holt inequality guarantees the generation of only 1.23 bits of randomness. We prove here that quantum correlations with arbitrarily little nonlocality and states with arbitrarily little entanglement can be used to certify that close to the maximum of 2 bits of randomness are produced. Our results show that nonlocality, entanglement, and randomness are inequivalent quantities. They also imply that device-independent quantum key distribution with an optimal key generation rate is possible by using almost-local correlations and that device-independent randomness generation with an optimal rate is possible with almost-local correlations and with almost-unentangled states.

  15. Optimal protocols for nonlocality distillation

    SciTech Connect

    Hoeyer, Peter; Rashid, Jibran

    2010-10-15

    Forster et al. recently showed that weak nonlocality can be amplified by giving the first protocol that distills a class of nonlocal boxes (NLBs) [Phys. Rev. Lett. 102, 120401 (2009)] We first show that their protocol is optimal among all nonadaptive protocols. We next consider adaptive protocols. We show that the depth-2 protocol of Allcock et al. [Phys. Rev. A 80, 062107 (2009)] performs better than previously known adaptive depth-2 protocols for all symmetric NLBs. We present a depth-3 protocol that extends the known region of distillable NLBs. We give examples of NLBs for which each of the Forster et al., the Allcock et al., and our protocols perform best. The understanding we develop is that there is no single optimal protocol for NLB distillation. The choice of which protocol to use depends on the noise parameters for the NLB.

  16. Non-Local Euclidean Medians.

    PubMed

    Chaudhury, Kunal N; Singer, Amit

    2012-11-01

    In this letter, we note that the denoising performance of Non-Local Means (NLM) can be improved at large noise levels by replacing the mean by the Euclidean median. We call this new denoising algorithm the Non-Local Euclidean Medians (NLEM). At the heart of NLEM is the observation that the median is more robust to outliers than the mean. In particular, we provide a simple geometric insight that explains why NLEM performs better than NLM in the vicinity of edges, particularly at large noise levels. NLEM can be efficiently implemented using iteratively reweighted least squares, and its computational complexity is comparable to that of NLM. We provide some preliminary results to study the proposed algorithm and to compare it with NLM.

  17. The accurate calculation of the band gap of liquid water by means of GW corrections applied to plane-wave density functional theory molecular dynamics simulations.

    PubMed

    Fang, Changming; Li, Wun-Fan; Koster, Rik S; Klimeš, Jiří; van Blaaderen, Alfons; van Huis, Marijn A

    2015-01-01

    Knowledge about the intrinsic electronic properties of water is imperative for understanding the behaviour of aqueous solutions that are used throughout biology, chemistry, physics, and industry. The calculation of the electronic band gap of liquids is challenging, because the most accurate ab initio approaches can be applied only to small numbers of atoms, while large numbers of atoms are required for having configurations that are representative of a liquid. Here we show that a high-accuracy value for the electronic band gap of water can be obtained by combining beyond-DFT methods and statistical time-averaging. Liquid water is simulated at 300 K using a plane-wave density functional theory molecular dynamics (PW-DFT-MD) simulation and a van der Waals density functional (optB88-vdW). After applying a self-consistent GW correction the band gap of liquid water at 300 K is calculated as 7.3 eV, in good agreement with recent experimental observations in the literature (6.9 eV). For simulations of phase transformations and chemical reactions in water or aqueous solutions whereby an accurate description of the electronic structure is required, we suggest to use these advanced GW corrections in combination with the statistical analysis of quantum mechanical MD simulations.

  18. X-ray absorption spectra of hexagonal ice and liquid water by all-electron Gaussian and augmented plane wave calculations.

    PubMed

    Iannuzzi, Marcella

    2008-05-28

    Full potential x-ray spectroscopy simulations of hexagonal ice and liquid water are performed by means of the newly implemented methodology based on the Gaussian augmented plane waves formalism. The computed spectra obtained within the supercell approach are compared to experimental data. The variations of the spectral distribution determined by the quality of the basis set, the size of the sample, and the choice of the core-hole potential are extensively discussed. The second part of this work is focused on the understanding of the connections between specific configurations of the hydrogen bond network and the corresponding contributions to the x-ray absorption spectrum in liquid water. Our results confirm that asymmetrically coordinated molecules, in particular, those donating only one or no hydrogen bond, are associated with well identified spectral signatures that differ significantly from the ice spectral profile. However, transient local structures, with half formed hydrogen bonds, may still give rise to spectra with dominant postedge contributions and relatively weaker oscillator strengths at lower energy. This explains why by averaging the spectra over all the O atoms of liquid instantaneous configurations extracted from ab initio molecular dynamics trajectories, the spectral features indicating the presence of weak or broken hydrogen bonds turn out to be attenuated and sometimes not clearly distinguishable.

  19. Tunable broadband plasmonic field enhancement on a graphene surface using a normal-incidence plane wave at mid-infrared frequencies.

    PubMed

    Zhang, Tian; Chen, Lin; Wang, Bing; Li, Xun

    2015-01-01

    We investigate optical field enhancement for a wide mid-infrared range, originating from the excitation of graphene plasmons, by introducing a graded dielectric grating of varying period underneath a graphene monolayer. Excitation of the plasmonic mode can be achieved by illuminating a normal-incidence plane wave on the gratings due to guided-mode resonance. The gratings of varying period enable the excitation of the plasmonic mode with a very high field enhancement factor (to the order of magnitude of 1000) within a wide spectral band, which leads to the frequency-dependent spatially separated localization of the infrared spectrum modes. We also demonstrate that the excitation position of the plasmonic mode can be freely tuned by varying the thickness of the interlayer as well as the chemical potential of the graphene monolayer. This structure enables the design of two-dimensional plasmonic photonic circuits and metamaterials targeted towards numerous potential applications including optoelectronic detectors, light-harvest devices, on-chip optical interconnects, biosensors, and light-matter interactions.

  20. Errors incurred in a plane-wave-type expansion of a Gaussian beam. [in laser force calculations on light scattering aerosol experiments

    NASA Technical Reports Server (NTRS)

    Kattawar, G. W.

    1980-01-01

    The multipole expansion obtained by Morita et al. (1968) of the Gaussian laser beam used to levitate an aerosol particle in order that its complete phase matrix may be measured is compared with that of Tsai and Pogorzelski (1975) in order to demonstrate the effect of the incorrect expansion used by Morita. Errors incurred by the use of an equation in which one side satisfies the scalar wave equation while the other side does not and can be reduced to a plane wave amplitude are calculated as functions of the inverse of the wave number times the beam waist, the wave number times the radial spherical coordinate and the angular spherical coordinate. Errors on the order of a few percent, considered undetectable are obtained in the squared-field amplitudes due to the expansion, however, they are found to become significant (several tens of percent) when the angle is zero. It is concluded that the expansion of Morita should only be used in the regions where the spherical angle is less than 0.01 and its product with the wave number and the radial spherical coordinate is less than unity.

  1. Calculations of Lamb wave band gaps and dispersions for piezoelectric phononic plates using mindlin's theory-based plane wave expansion method.

    PubMed

    Hsu, Jin-Chen; Wu, Tsung-Tsong

    2008-02-01

    Based on Mindlin's piezoelectric plate theory and the plane wave expansion method, a formulation is proposed to study the frequency band gaps and dispersion relations of the lower-order Lamb waves in two-dimensional piezoelectric phononic plates. The method is applied to analyze the phononic plates composed of solid-solid and airsolid constituents with square and triangular lattices, respectively. Factors that influence the opening and width of the complete Lamb wave gaps are identified and discussed. For solid/solid phononic plates, it is suggested that the filling material be chosen with larger mass density, proper stiffness, and weak anisotropic factor embedded in a soft matrix in order to obtain wider complete band gaps of the lower-order Lamb waves. By comparing to the calculated results without considering the piezoelectricity, the influences of piezoelectric effect on Lamb waves are analyzed as well. On the other hand, for air/solid phononic plates, a background material itself with proper anisotropy and a high filling fraction of air may favor the opening of the complete Lamb wave gaps.

  2. Improving the accuracy of ground-state correlation energies within a plane-wave basis set: The electron-hole exchange kernel

    NASA Astrophysics Data System (ADS)

    Dixit, Anant; Ángyán, János G.; Rocca, Dario

    2016-09-01

    A new formalism was recently proposed to improve random phase approximation (RPA) correlation energies by including approximate exchange effects [B. Mussard et al., J. Chem. Theory Comput. 12, 2191 (2016)]. Within this framework, by keeping only the electron-hole contributions to the exchange kernel, two approximations can be obtained: An adiabatic connection analog of the second order screened exchange (AC-SOSEX) and an approximate electron-hole time-dependent Hartree-Fock (eh-TDHF). Here we show how this formalism is suitable for an efficient implementation within the plane-wave basis set. The response functions involved in the AC-SOSEX and eh-TDHF equations can indeed be compactly represented by an auxiliary basis set obtained from the diagonalization of an approximate dielectric matrix. Additionally, the explicit calculation of unoccupied states can be avoided by using density functional perturbation theory techniques and the matrix elements of dynamical response functions can be efficiently computed by applying the Lanczos algorithm. As shown by several applications to reaction energies and weakly bound dimers, the inclusion of the electron-hole kernel significantly improves the accuracy of ground-state correlation energies with respect to RPA and semi-local functionals.

  3. Scattering of s-polarized electromagnetic plane waves from a film with a shallow random rough surface on a perfect conductor.

    PubMed

    García-Llamas, R; Márquez-Beltran, C

    2000-09-01

    Scattering of s-polarized electromagnetic planes waves from a film, with a shallow random rough one-dimensional surface, bounded by vacuum and a perfect conductor is calculated. An integral equation that relates the amplitude of the scattered field to the incident wave is found by use of the Rayleigh hypothesis. The integral equation is solved numerically and by use of the perturbation theory, up to the fourth order in the surface profile function. In the angular dependence of the incoherent part of the differential reflection coefficient, the backscattering peak and two additional satellite peaks are observed, owing to two guided waves supported by the film. Analysis of the perturbation solution reveals that the background scattering exhibits minima and maxima as functions of the thickness. By studying the behavior of the scattering as a function of the absorption index of the film, it is shown that the amplitudes of the peaks are low when k approximately 10(-2) and high when k approximately 10(-4).

  4. Hybrid Fast Fourier Transform-plane wave based near-field far-field transformation for “body of revolution” antenna measurement grids

    NASA Astrophysics Data System (ADS)

    Schmidt, C. H.; Laitinen, T. A.; Eibert, T. F.

    2011-10-01

    Near-field measurement and transformation techniques are widely applied to characterize radiation patterns of antennas. Spherical and cylindrical near-field measurements have been researched extensively and various techniques with different probe compensation capabilities and complexities exist. Among those techniques applicable for (almost) arbitrary probes, the crucial computational efficiency has been achieved through the use of Fast Fourier Transform based preprocessing of the measurement data. It is shown in this paper that the Fast Fourier Transform based preprocessing can also be utilized in conjunction with the plane wave based fully probe-corrected near-field far-field transformation with low numerical complexity. The collection of probe signals is split into smaller subsets for individual orthogonal azimuthal Fourier modes by an Inverse Fast Fourier Transform. These smaller subsets can be transformed to the far field very efficiently with full probe correction. The technique presented in this paper is applicable for arbitrary "body of revolution" antenna measurement grids, including the important cases of cylindrical and spherical measurement grids. The "body of revolution" grids are rotationally symmetric around the z-axis and the probe signals must be available equidistantly in ϕ.

  5. Performance of plane-wave-based LDA+U and GGA+U approaches to describe magnetic coupling in molecular systems.

    PubMed

    Rivero, Pablo; Loschen, Christoph; Moreira, Ibério De P R; Illas, Francesc

    2009-11-15

    This work explores the performance of periodic plane wave density functional theory calculations with an on-site Coulomb correction to the standard LDA and GGA exchange-correlation potential--commonly used to describe strongly correlated solids--in describing the magnetic coupling constant of a series of molecular compounds representative of dinuclear Cu complexes and of organic diradicals. The resulting LDA+U or GGA+U formalisms, lead to results comparable to experiment and to those obtained by means of standard hybrid functionals provided that the value of the U parameter is adequately chosen. Hence, these methods offer an alternative efficient computational scheme to correct LDA and GGA approaches to adequately describe the electronic structure and magnetic coupling in large molecular magnetic systems, although at the expenses of introducing an empirical (U) parameter. For all investigated copper dinuclear systems, the LDA+U and GGA+U approaches lead to an improvement in the description of magnetic properties over the original LDA and GGA schemes with an accuracy similar to that arising from the hybrid B3LYP functional, by increasing the on-site Coulomb repulsion with a moderate U value. Nevertheless, the introduction of an arbitrary U value in the 0-10 eV range most often provides the correct ground-state spin distribution and the correct sign of the magnetic coupling constant.

  6. Improving the accuracy of ground-state correlation energies within a plane-wave basis set: The electron-hole exchange kernel.

    PubMed

    Dixit, Anant; Ángyán, János G; Rocca, Dario

    2016-09-14

    A new formalism was recently proposed to improve random phase approximation (RPA) correlation energies by including approximate exchange effects [B. Mussard et al., J. Chem. Theory Comput. 12, 2191 (2016)]. Within this framework, by keeping only the electron-hole contributions to the exchange kernel, two approximations can be obtained: An adiabatic connection analog of the second order screened exchange (AC-SOSEX) and an approximate electron-hole time-dependent Hartree-Fock (eh-TDHF). Here we show how this formalism is suitable for an efficient implementation within the plane-wave basis set. The response functions involved in the AC-SOSEX and eh-TDHF equations can indeed be compactly represented by an auxiliary basis set obtained from the diagonalization of an approximate dielectric matrix. Additionally, the explicit calculation of unoccupied states can be avoided by using density functional perturbation theory techniques and the matrix elements of dynamical response functions can be efficiently computed by applying the Lanczos algorithm. As shown by several applications to reaction energies and weakly bound dimers, the inclusion of the electron-hole kernel significantly improves the accuracy of ground-state correlation energies with respect to RPA and semi-local functionals. PMID:27634249

  7. X-ray absorption spectra of hexagonal ice and liquid water by all-electron Gaussian and augmented plane wave calculations

    NASA Astrophysics Data System (ADS)

    Iannuzzi, Marcella

    2008-05-01

    Full potential x-ray spectroscopy simulations of hexagonal ice and liquid water are performed by means of the newly implemented methodology based on the Gaussian augmented plane waves formalism. The computed spectra obtained within the supercell approach are compared to experimental data. The variations of the spectral distribution determined by the quality of the basis set, the size of the sample, and the choice of the core-hole potential are extensively discussed. The second part of this work is focused on the understanding of the connections between specific configurations of the hydrogen bond network and the corresponding contributions to the x-ray absorption spectrum in liquid water. Our results confirm that asymmetrically coordinated molecules, in particular, those donating only one or no hydrogen bond, are associated with well identified spectral signatures that differ significantly from the ice spectral profile. However, transient local structures, with half formed hydrogen bonds, may still give rise to spectra with dominant postedge contributions and relatively weaker oscillator strengths at lower energy. This explains why by averaging the spectra over all the O atoms of liquid instantaneous configurations extracted from ab initio molecular dynamics trajectories, the spectral features indicating the presence of weak or broken hydrogen bonds turn out to be attenuated and sometimes not clearly distinguishable.

  8. Fourth-moment calculation of optical propagation in a turbulent atmosphere with use of the split-step method. I. Plane wave

    SciTech Connect

    Jenu, M.Z.M.; Bebbington, D.H.O.

    1994-11-01

    The split-step method was used to derive the full spatial dependence of the fourth moment of a plane-wave propagating in a two-dimensional turbulent atmosphere with a power-law spectrum for two values of the scattering parameter {gamma}{sub {ital k}} = 0 and 1 [J. Opt. Soc. Am. A {bold 2}, 2133 (1985)]. The changes in {gamma}{sub {ital k}} were obtained by the use of two different values of the inner scale of turbulence {ital l}{sub 0} while the operating wavelength and turbulent strength were kept constant. In this way the influence of {ital l}{sub 0} on the field statistics can be obtained. The results of intensity scintillation index {sigma}{sub {ital I}}{sup 2} and covariance function {ital b}{sub {ital I}} are also presented. The agreement of {sigma}{sub {ital I}}{sup 2} with the results of the reference cited above especially for {gamma}{sub {ital k}} = 0 is good. We also used the results of {ital b}{sub {ital I}} to study the asymptotic dependence of the characteristic correlation length on {zeta}, where {zeta} is the propagation-range scale.

  9. Tunable broadband plasmonic field enhancement on a graphene surface using a normal-incidence plane wave at mid-infrared frequencies

    PubMed Central

    Zhang, Tian; Chen, Lin; Wang, Bing; Li, Xun

    2015-01-01

    We investigate optical field enhancement for a wide mid-infrared range, originating from the excitation of graphene plasmons, by introducing a graded dielectric grating of varying period underneath a graphene monolayer. Excitation of the plasmonic mode can be achieved by illuminating a normal-incidence plane wave on the gratings due to guided-mode resonance. The gratings of varying period enable the excitation of the plasmonic mode with a very high field enhancement factor (to the order of magnitude of 1000) within a wide spectral band, which leads to the frequency-dependent spatially separated localization of the infrared spectrum modes. We also demonstrate that the excitation position of the plasmonic mode can be freely tuned by varying the thickness of the interlayer as well as the chemical potential of the graphene monolayer. This structure enables the design of two-dimensional plasmonic photonic circuits and metamaterials targeted towards numerous potential applications including optoelectronic detectors, light-harvest devices, on-chip optical interconnects, biosensors, and light-matter interactions. PMID:26057188

  10. Temporal nonlocality in bistable perception

    NASA Astrophysics Data System (ADS)

    Atmanspacher, Harald; Filk, Thomas

    2012-12-01

    A novel conceptual framework for theoretical psychology is presented and illustrated for the example of bistable perception. A basic formal feature of this framework is the non-commutativity of operations acting on mental states. A corresponding model for the bistable perception of ambiguous stimuli, the Necker-Zeno model, is sketched and some empirical evidence for it so far is described. It is discussed how a temporal nonlocality of mental states, predicted by the model, can be understood and tested.

  11. Quantum nonlocality does not exist

    PubMed Central

    Tipler, Frank J.

    2014-01-01

    Quantum nonlocality is shown to be an artifact of the Copenhagen interpretation, in which each observed quantity has exactly one value at any instant. In reality, all physical systems obey quantum mechanics, which obeys no such rule. Locality is restored if observed and observer are both assumed to obey quantum mechanics, as in the many-worlds interpretation (MWI). Using the MWI, I show that the quantum side of Bell’s inequality, generally believed nonlocal, is really due to a series of three measurements (not two as in the standard, oversimplified analysis), all three of which have only local effects. Thus, experiments confirming “nonlocality” are actually confirming the MWI. The mistaken interpretation of nonlocality experiments depends crucially on a question-begging version of the Born interpretation, which makes sense only in “collapse” versions of quantum theory, about the meaning of the modulus of the wave function, so I use the interpretation based on the MWI, namely that the wave function is a world density amplitude, not a probability amplitude. This view allows the Born interpretation to be derived directly from the Schrödinger equation, by applying the Schrödinger equation to both the observed and the observer. PMID:25015084

  12. Pseudopotential multi-relaxation-time lattice Boltzmann model for cavitation bubble collapse with high density ratio

    NASA Astrophysics Data System (ADS)

    Shan, Ming-Lei; Zhu, Chang-Ping; Yao, Cheng; Yin, Cheng; Jiang, Xiao-Yan

    2016-10-01

    The dynamics of the cavitation bubble collapse is a fundamental issue for the bubble collapse application and prevention. In the present work, the modified forcing scheme for the pseudopotential multi-relaxation-time lattice Boltzmann model developed by Li Q et al. [Li Q, Luo K H and Li X J 2013 Phys. Rev. E 87 053301] is adopted to develop a cavitation bubble collapse model. In the respects of coexistence curves and Laplace law verification, the improved pseudopotential multi-relaxation-time lattice Boltzmann model is investigated. It is found that the thermodynamic consistency and surface tension are independent of kinematic viscosity. By homogeneous and heterogeneous cavitation simulation, the ability of the present model to describe the cavitation bubble development as well as the cavitation inception is verified. The bubble collapse between two parallel walls is simulated. The dynamic process of a collapsing bubble is consistent with the results from experiments and simulations by other numerical methods. It is demonstrated that the present pseudopotential multi-relaxation-time lattice Boltzmann model is applicable and efficient, and the lattice Boltzmann method is an alternative tool for collapsing bubble modeling. Project supported by the National Natural Science Foundation of China (Grant Nos. 11274092 and 1140040119) and the Natural Science Foundation of Jiangsu Province, China (Grant No. SBK2014043338).

  13. Accuracy of relativistic energy-consistent pseudopotentials for superheavy elements 111-118: Molecular calibration calculations

    SciTech Connect

    Hangele, Tim; Dolg, Michael

    2013-01-28

    Relativistic energy-consistent pseudopotentials modelling the Dirac-Coulomb-Breit Hamiltonian with a finite nucleus model for the superheavy elements with nuclear charges 111-118 were calibrated in atomic and molecular calculations against fully relativistic all-electron reference data. Various choices for the adjustment of the f-potentials were investigated and an improved parametrization is recommended. Using the resulting pseudopotentials relativistic all-electron reference data can be reproduced at the self-consistent field level with average absolute (relative) errors of 0.0030 A (0.15%) for bond lengths and 2.79 N m{sup -1} (1.26%) for force constants for 24 diatomic test molecules, i.e., neutral or singly charged monohydrides, monofluorides, and monochlorides with closed-shell electronic structure. At the second-order Moller-Plesset perturbation theory level the corresponding average deviations are 0.0033 A (0.15%) for bond lengths and 2.86 N m{sup -1} (1.40%) for force constants. Corresponding improved f-potentials were also derived for the pseudopotentials modelling in addition the leading contributions from quantum electrodynamics.

  14. Frustrated Brownian Motion of Nonlocal Solitary Waves

    SciTech Connect

    Folli, V.; Conti, C.

    2010-05-14

    We investigate the evolution of solitary waves in a nonlocal medium in the presence of disorder. By using a perturbational approach, we show that an increasing degree of nonlocality may largely hamper the Brownian motion of self-trapped wave packets. The result is valid for any kind of nonlocality and in the presence of nonparaxial effects. Analytical predictions are compared with numerical simulations based on stochastic partial differential equations.

  15. Nonlocality and entanglement in the XY model

    SciTech Connect

    Batle, J.; Casas, M.

    2010-12-15

    Nonlocality and quantum entanglement constitute two special features of quantum systems of paramount importance in quantum-information theory (QIT). Essentially regarded as identical or equivalent for many years, they constitute different concepts. Describing nonlocality by means of the maximal violation of two Bell inequalities, we study both entanglement and nonlocality for two and three spins in the XY model. Our results shed light on the description of nonlocality and the possible information-theoretic task limitations of entanglement in an infinite quantum system.

  16. Nonlocal gravity in the solar system

    NASA Astrophysics Data System (ADS)

    Chicone, C.; Mashhoon, B.

    2016-04-01

    The implications of the recent classical nonlocal generalization of Einstein’s theory of gravitation for gravitational physics in the solar system are investigated. In this theory, the nonlocal character of gravity appears to simulate dark matter. Nonlocal gravity in the Newtonian regime involves a reciprocal kernel with three spatial parameters, of which two have already been determined from the rotation curves of spiral galaxies and the internal dynamics of clusters of galaxies. However, the short-range parameter a 0 remains to be determined. In this connection, the nonlocal contribution to the perihelion precession of a planetary orbit is estimated and a preliminary lower limit on a 0 is determined.

  17. Origin of Dynamical Quantum Non-locality

    NASA Astrophysics Data System (ADS)

    Pachon, Cesar E.; Pachon, Leonardo A.

    2014-03-01

    Non-locality is one of the hallmarks of quantum mechanics and is responsible for paradigmatic features such as entanglement and the Aharonov-Bohm effect. Non-locality comes in two ``flavours'': a kinematic non-locality- arising from the structure of the Hilbert space- and a dynamical non-locality- arising from the quantum equations of motion-. Kinematic non-locality is unable to induce any change in the probability distributions, so that the ``action-at-a-distance'' cannot manifest. Conversely, dynamical non-locality does create explicit changes in probability, though in a ``causality-preserving'' manner. The origin of non-locality of quantum measurements and its relations to the fundamental postulates of quantum mechanics, such as the uncertainty principle, have been only recently elucidated. Here we trace the origin of dynamical non-locality to the superposition principle. This relation allows us to establish and identify how the uncertainty and the superposition principles determine the non-local character of the outcome of a quantum measurement. Being based on group theoretical and path integral formulations, our formulation admits immediate generalizations and extensions to to, e.g., quantum field theory. This work was supported by the Departamento Administrativo de Ciencia, Tecnologia e Innovacion -COLCIENCIAS- of Colombia under the grant number 111556934912.

  18. First evidence of non-locality in real band-gap metamaterials: determining parameters in the relaxed micromorphic model

    NASA Astrophysics Data System (ADS)

    Madeo, Angela; Barbagallo, Gabriele; d'Agostino, Marco Valerio; Placidi, Luca; Neff, Patrizio

    2016-06-01

    In this paper, we propose the first estimate of some elastic parameters of the relaxed micromorphic model on the basis of real experiments of transmission of longitudinal plane waves across an interface separating a classical Cauchy material (steel plate) and a phononic crystal (steel plate with fluid-filled holes). A procedure is set up in order to identify the parameters of the relaxed micromorphic model by superimposing the experimentally based profile of the reflection coefficient (plotted as function of the wave-frequency) with the analogous profile obtained via numerical simulations. We determine five out of six constitutive parameters which are featured by the relaxed micromorphic model in the isotropic case, plus the determination of the micro-inertia parameter. The sixth elastic parameter, namely the Cosserat couple modulus μc, still remains undetermined, since experiments on transverse incident waves are not yet available. A fundamental result of this paper is the estimate of the non-locality intrinsically associated with the underlying microstructure of the metamaterial. We show that the characteristic length Lc measuring the non-locality of the phononic crystal is of the order of 1/3 of the diameter of its fluid-filled holes.

  19. Forces and stress in second order Møller-Plesset perturbation theory for condensed phase systems within the resolution-of-identity Gaussian and plane waves approach

    SciTech Connect

    Del Ben, Mauro Hutter, Jürg; VandeVondele, Joost

    2015-09-14

    The forces acting on the atoms as well as the stress tensor are crucial ingredients for calculating the structural and dynamical properties of systems in the condensed phase. Here, these derivatives of the total energy are evaluated for the second-order Møller-Plesset perturbation energy (MP2) in the framework of the resolution of identity Gaussian and plane waves method, in a way that is fully consistent with how the total energy is computed. This consistency is non-trivial, given the different ways employed to compute Coulomb, exchange, and canonical four center integrals, and allows, for example, for energy conserving dynamics in various ensembles. Based on this formalism, a massively parallel algorithm has been developed for finite and extended system. The designed parallel algorithm displays, with respect to the system size, cubic, quartic, and quintic requirements, respectively, for the memory, communication, and computation. All these requirements are reduced with an increasing number of processes, and the measured performance shows excellent parallel scalability and efficiency up to thousands of nodes. Additionally, the computationally more demanding quintic scaling steps can be accelerated by employing graphics processing units (GPU’s) showing, for large systems, a gain of almost a factor two compared to the standard central processing unit-only case. In this way, the evaluation of the derivatives of the RI-MP2 energy can be performed within a few minutes for systems containing hundreds of atoms and thousands of basis functions. With good time to solution, the implementation thus opens the possibility to perform molecular dynamics (MD) simulations in various ensembles (microcanonical ensemble and isobaric-isothermal ensemble) at the MP2 level of theory. Geometry optimization, full cell relaxation, and energy conserving MD simulations have been performed for a variety of molecular crystals including NH{sub 3}, CO{sub 2}, formic acid, and benzene.

  20. Forces and stress in second order Møller-Plesset perturbation theory for condensed phase systems within the resolution-of-identity Gaussian and plane waves approach.

    PubMed

    Del Ben, Mauro; Hutter, Jürg; VandeVondele, Joost

    2015-09-14

    The forces acting on the atoms as well as the stress tensor are crucial ingredients for calculating the structural and dynamical properties of systems in the condensed phase. Here, these derivatives of the total energy are evaluated for the second-order Møller-Plesset perturbation energy (MP2) in the framework of the resolution of identity Gaussian and plane waves method, in a way that is fully consistent with how the total energy is computed. This consistency is non-trivial, given the different ways employed to compute Coulomb, exchange, and canonical four center integrals, and allows, for example, for energy conserving dynamics in various ensembles. Based on this formalism, a massively parallel algorithm has been developed for finite and extended system. The designed parallel algorithm displays, with respect to the system size, cubic, quartic, and quintic requirements, respectively, for the memory, communication, and computation. All these requirements are reduced with an increasing number of processes, and the measured performance shows excellent parallel scalability and efficiency up to thousands of nodes. Additionally, the computationally more demanding quintic scaling steps can be accelerated by employing graphics processing units (GPU's) showing, for large systems, a gain of almost a factor two compared to the standard central processing unit-only case. In this way, the evaluation of the derivatives of the RI-MP2 energy can be performed within a few minutes for systems containing hundreds of atoms and thousands of basis functions. With good time to solution, the implementation thus opens the possibility to perform molecular dynamics (MD) simulations in various ensembles (microcanonical ensemble and isobaric-isothermal ensemble) at the MP2 level of theory. Geometry optimization, full cell relaxation, and energy conserving MD simulations have been performed for a variety of molecular crystals including NH3, CO2, formic acid, and benzene.

  1. Forces and stress in second order Møller-Plesset perturbation theory for condensed phase systems within the resolution-of-identity Gaussian and plane waves approach

    NASA Astrophysics Data System (ADS)

    Del Ben, Mauro; Hutter, Jürg; VandeVondele, Joost

    2015-09-01

    The forces acting on the atoms as well as the stress tensor are crucial ingredients for calculating the structural and dynamical properties of systems in the condensed phase. Here, these derivatives of the total energy are evaluated for the second-order Møller-Plesset perturbation energy (MP2) in the framework of the resolution of identity Gaussian and plane waves method, in a way that is fully consistent with how the total energy is computed. This consistency is non-trivial, given the different ways employed to compute Coulomb, exchange, and canonical four center integrals, and allows, for example, for energy conserving dynamics in various ensembles. Based on this formalism, a massively parallel algorithm has been developed for finite and extended system. The designed parallel algorithm displays, with respect to the system size, cubic, quartic, and quintic requirements, respectively, for the memory, communication, and computation. All these requirements are reduced with an increasing number of processes, and the measured performance shows excellent parallel scalability and efficiency up to thousands of nodes. Additionally, the computationally more demanding quintic scaling steps can be accelerated by employing graphics processing units (GPU's) showing, for large systems, a gain of almost a factor two compared to the standard central processing unit-only case. In this way, the evaluation of the derivatives of the RI-MP2 energy can be performed within a few minutes for systems containing hundreds of atoms and thousands of basis functions. With good time to solution, the implementation thus opens the possibility to perform molecular dynamics (MD) simulations in various ensembles (microcanonical ensemble and isobaric-isothermal ensemble) at the MP2 level of theory. Geometry optimization, full cell relaxation, and energy conserving MD simulations have been performed for a variety of molecular crystals including NH3, CO2, formic acid, and benzene.

  2. More nonlocality with less entanglement

    SciTech Connect

    Vidick, Thomas; Wehner, Stephanie

    2011-05-15

    Recent numerical investigations [K. Pal and T. Vertesi, Phys. Rev. A 82, 022116 (2010)] suggest that the I3322 inequality, arguably the simplest extremal Bell inequality after the CHSH inequality, has a very rich structure in terms of the entangled states and measurements that maximally violate it. Here we show that for this inequality the maximally entangled state of any dimension achieves the same violation than just a single EPR pair. In contrast, stronger violations can be achieved using higher dimensional states which are less entangled. This shows that the maximally entangled state is not the most nonlocal resource, even when one restricts attention to the most simple extremal Bell inequalities.

  3. Virial Theorem in Nonlocal Newtonian Gravity

    NASA Astrophysics Data System (ADS)

    Mashhoon, Bahram

    2016-05-01

    Nonlocal gravity is the recent classical nonlocal generalization of Einstein's theory of gravitation in which the past history of the gravitational field is taken into account. In this theory, nonlocality appears to simulate dark matter. The virial theorem for the Newtonian regime of nonlocal gravity theory is derived and its consequences for "isolated" astronomical systems in virial equilibrium at the present epoch are investigated. In particular, for a sufficiently isolated nearby galaxy in virial equilibrium, the galaxy's baryonic diameter---namely, the diameter of the smallest sphere that completely surrounds the baryonic system at the present time---is predicted to be larger than the effective dark matter fraction times a universal length that is the basic nonlocality length scale of about 3 kpc.

  4. Hyperbolic metamaterial lens with hydrodynamic nonlocal response.

    PubMed

    Yan, Wei; Mortensen, N Asger; Wubs, Martijn

    2013-06-17

    We investigate the effects of hydrodynamic nonlocal response in hyperbolic metamaterials (HMMs), focusing on the experimentally realizable parameter regime where unit cells are much smaller than an optical wavelength but much larger than the wavelengths of the longitudinal pressure waves of the free-electron plasma in the metal constituents. We derive the nonlocal corrections to the effective material parameters analytically, and illustrate the noticeable nonlocal effects on the dispersion curves numerically. As an application, we find that the focusing characteristics of a HMM lens in the local-response approximation and in the hydrodynamic Drude model can differ considerably. In particular, the optimal frequency for imaging in the nonlocal theory is blueshifted with respect to that in the local theory. Thus, to detect whether nonlocal response is at work in a hyperbolic metamaterial, we propose to measure the near-field distribution of a hyperbolic metamaterial lens. PMID:23787690

  5. Band structure calculation of GaSe-based nanostructures using empirical pseudopotential method

    NASA Astrophysics Data System (ADS)

    Osadchy, A. V.; Volotovskiy, S. G.; Obraztsova, E. D.; Savin, V. V.; Golovashkin, D. L.

    2016-08-01

    In this paper we present the results of band structure computer simulation of GaSe- based nanostructures using the empirical pseudopotential method. Calculations were performed using a specially developed software that allows performing simulations using cluster computing. Application of this method significantly reduces the demands on computing resources compared to traditional approaches based on ab-initio techniques and provides receiving the adequate comparable results. The use of cluster computing allows to obtain information for structures that require an explicit account of a significant number of atoms, such as quantum dots and quantum pillars.

  6. The relationship between specific absorption rate and temperature elevation in anatomically based human body models for plane wave exposure from 30 MHz to 6 GHz

    NASA Astrophysics Data System (ADS)

    Hirata, Akimasa; Laakso, Ilkka; Oizumi, Takuya; Hanatani, Ryuto; Chan, Kwok Hung; Wiart, Joe

    2013-02-01

    According to the international safety guidelines/standard, the whole-body-averaged specific absorption rate (Poljak et al 2003 IEEE Trans. Electromagn. Compat. 45 141-5) and the peak spatial average SAR are used as metrics for human protection from whole-body and localized exposures, respectively. The IEEE standard (IEEE 2006 IEEE C95.1) indicates that the upper boundary frequency, over which the whole-body-averaged SAR is deemed to be the basic restriction, has been reduced from 6 to 3 GHz, because radio-wave energy is absorbed around the body surface when the frequency is increased. However, no quantitative discussion has been provided to support this description especially from the standpoint of temperature elevation. It is of interest to investigate the maximum temperature elevation in addition to the core temperature even for a whole-body exposure. In the present study, using anatomically based human models, we computed the SAR and the temperature elevation for a plane-wave exposure from 30 MHz to 6 GHz, taking into account the thermoregulatory response. As the primary result, we found that the ratio of the core temperature elevation to the whole-body-averaged SAR is almost frequency independent for frequencies below a few gigahertz; the ratio decreases above this frequency. At frequencies higher than a few gigahertz, core temperature elevation for the same whole-body averaged SAR becomes lower due to heat convection from the skin to air. This lower core temperature elevation is attributable to skin temperature elevation caused by the power absorption around the body surface. Then, core temperature elevation even for whole-body averaged SAR of 4 W kg-1 with the duration of 1 h was at most 0.8 °C, which is smaller than a threshold considered in the safety guidelines/standard. Further, the peak 10 g averaged SAR is correlated with the maximum body temperature elevations without extremities and pinna over the frequencies considered. These findings were confirmed

  7. Can EPR non-locality be geometrical?

    SciTech Connect

    Ne`eman, Y. |; Botero, A.

    1995-10-01

    The presence in Quantum Mechanics of non-local correlations is one of the two fundamentally non-intuitive features of that theory. The non-local correlations themselves fall into two classes: EPR and Geometrical. The non-local characteristics of the geometrical type are well-understood and are not suspected of possibly generating acausal features, such as faster-than-light propagation of information. This has especially become true since the emergence of a geometrical treatment for the relevant gauge theories, i.e. Fiber Bundle geometry, in which the quantum non-localities are seen to correspond to pure homotopy considerations. This aspect is reviewed in section 2. Contrary-wise, from its very conception, the EPR situation was felt to be paradoxical. It has been suggested that the non-local features of EPR might also derive from geometrical considerations, like all other non-local characteristics of QM. In[7], one of the authors was able to point out several plausibility arguments for this thesis, emphasizing in particular similarities between the non-local correlations provided by any gauge field theory and those required by the preservation of the quantum numbers of the original EPR state-vector, throughout its spatially-extended mode. The derivation was, however, somewhat incomplete, especially because of the apparent difference between, on the one hand, the closed spatial loops arising in the analysis of the geometrical non-localities, from Aharonov-Bohm and Berry phases to magnetic monopoles and instantons, and on the other hand, in the EPR case, the open line drawn by the positions of the two moving decay products of the disintegrating particle. In what follows, the authors endeavor to remove this obstacle and show that as in all other QM non-localities, EPR is somehow related to closed loops, almost involving homotopy considerations. They develop this view in section 3.

  8. Generalized pseudopotentials as a way to restore the consistency of the Hartree-Fock-Bogoliubov formalism

    NASA Astrophysics Data System (ADS)

    Olshanii, Maxim; Pricoupenko, Ludovic

    2001-05-01

    We introduce a novel one-parametric family of zero-range pseudopotentials hatV^Λ(r) = g_Λ δ(r) [ partialr + Λ ] (r \\cdot ) with g_Λ = fracg_01-Λ a and g0 = 4πhbar^2 a/m , whose scattering length a does not depend on the free parameter Λ. No exact (after the zero-range approximation has been made) many-body observable depends on it, although approximate treatments differ for different Λ (M. Olshanii and L. Pricoupenko, ). We incorporate these pseudopotentials in the Hartree-Fock-Bogoliubov variational formalism, whose conventional (Λ=0) version is known to exhibit UV-divergencies, inconsistencies with both Hugenholtz-Pines theorem and many-body T-matrix calculations, and inability to develop an energy minimum for the atomic condensate leading to a molecular condensate instead. Using Λ as a new variational parameter we resolve all inconsistencies of the Hartree-Fock-Bogoliubov formalism known so far, with no ad hoc modifications of the theory.

  9. Local, nonlocal quantumness and information theoretic measures

    NASA Astrophysics Data System (ADS)

    Agrawal, Pankaj; Sazim, Sk; Chakrabarty, Indranil; Pati, Arun K.

    2016-08-01

    It has been suggested that there may exist quantum correlations that go beyond entanglement. The existence of such correlations can be revealed by information theoretic quantities such as quantum discord, but not by the conventional measures of entanglement. We argue that a state displays quantumness, that can be of local and nonlocal origin. Information theoretic measures not only characterize the nonlocal quantumness, but also the local quantumness, such as the “local superposition”. This can be a reason, why such measures are nonzero, when there is no entanglement. We consider a generalized version of the Werner state to demonstrate the interplay of local quantumness, nonlocal quantumness and classical mixedness of a state.

  10. Nonlocal Shear Stress for Homogeneous Fluids

    NASA Astrophysics Data System (ADS)

    Todd, B. D.; Hansen, J. S.; Daivis, Peter J.

    2008-05-01

    It has been suggested that for fluids in which the rate of strain varies appreciably over length scales of the order of the intermolecular interaction range, the viscosity must be treated as a nonlocal property of the fluid. The shear stress can then be postulated to be a convolution of this nonlocal viscosity kernel with the strain rate over all space. In this Letter, we confirm that this postulate is correct by a combination of analytical and numerical methods for an atomic fluid out of equilibrium. Furthermore, we show that a gradient expansion of the nonlocal constitutive equation gives a reasonable approximation to the shear stress in the small wave vector limit.

  11. All entangled quantum states are nonlocal.

    PubMed

    Buscemi, Francesco

    2012-05-18

    Departing from the usual paradigm of local operations and classical communication adopted in entanglement theory, we study here the interconversion of quantum states by means of local operations and shared randomness. A set of necessary and sufficient conditions for the existence of such a transformation between two given quantum states is given in terms of the payoff they yield in a suitable class of nonlocal games. It is shown that, as a consequence of our result, such a class of nonlocal games is able to witness quantum entanglement, however weak, and reveal nonlocality in any entangled quantum state. An example illustrating this fact is provided.

  12. Nonlocality in uniaxially polarizable media

    NASA Astrophysics Data System (ADS)

    Gorlach, Maxim A.; Belov, Pavel A.

    2015-08-01

    We reveal extraordinary electromagnetic properties for a general class of uniaxially polarizable media. Depending on parameters, such metamaterials may have a wide range of nontrivial shapes of isofrequency contours including lemniscate, diamond, and multiply connected curves with connectivity number reaching 5. The possibility of the dispersion engineering paves a way to more flexible manipulation of electromagnetic waves. Employing first-principles considerations we prove that uniaxially polarizable media should be described in terms of the nonlocal permittivity tensor which by no means can be reduced to local permittivity and permeability even in the long-wavelength limit. We introduce an alternative set of local material parameters including quadrupole susceptibility capable of capturing all of the second-order spatial dispersion effects.

  13. Experimental test of nonlocal causality

    PubMed Central

    Ringbauer, Martin; Giarmatzi, Christina; Chaves, Rafael; Costa, Fabio; White, Andrew G.; Fedrizzi, Alessandro

    2016-01-01

    Explaining observations in terms of causes and effects is central to empirical science. However, correlations between entangled quantum particles seem to defy such an explanation. This implies that some of the fundamental assumptions of causal explanations have to give way. We consider a relaxation of one of these assumptions, Bell’s local causality, by allowing outcome dependence: a direct causal influence between the outcomes of measurements of remote parties. We use interventional data from a photonic experiment to bound the strength of this causal influence in a two-party Bell scenario, and observational data from a Bell-type inequality test for the considered models. Our results demonstrate the incompatibility of quantum mechanics with a broad class of nonlocal causal models, which includes Bell-local models as a special case. Recovering a classical causal picture of quantum correlations thus requires an even more radical modification of our classical notion of cause and effect. PMID:27532045

  14. Experimental test of nonlocal causality.

    PubMed

    Ringbauer, Martin; Giarmatzi, Christina; Chaves, Rafael; Costa, Fabio; White, Andrew G; Fedrizzi, Alessandro

    2016-08-01

    Explaining observations in terms of causes and effects is central to empirical science. However, correlations between entangled quantum particles seem to defy such an explanation. This implies that some of the fundamental assumptions of causal explanations have to give way. We consider a relaxation of one of these assumptions, Bell's local causality, by allowing outcome dependence: a direct causal influence between the outcomes of measurements of remote parties. We use interventional data from a photonic experiment to bound the strength of this causal influence in a two-party Bell scenario, and observational data from a Bell-type inequality test for the considered models. Our results demonstrate the incompatibility of quantum mechanics with a broad class of nonlocal causal models, which includes Bell-local models as a special case. Recovering a classical causal picture of quantum correlations thus requires an even more radical modification of our classical notion of cause and effect. PMID:27532045

  15. Experimental test of nonlocal causality.

    PubMed

    Ringbauer, Martin; Giarmatzi, Christina; Chaves, Rafael; Costa, Fabio; White, Andrew G; Fedrizzi, Alessandro

    2016-08-01

    Explaining observations in terms of causes and effects is central to empirical science. However, correlations between entangled quantum particles seem to defy such an explanation. This implies that some of the fundamental assumptions of causal explanations have to give way. We consider a relaxation of one of these assumptions, Bell's local causality, by allowing outcome dependence: a direct causal influence between the outcomes of measurements of remote parties. We use interventional data from a photonic experiment to bound the strength of this causal influence in a two-party Bell scenario, and observational data from a Bell-type inequality test for the considered models. Our results demonstrate the incompatibility of quantum mechanics with a broad class of nonlocal causal models, which includes Bell-local models as a special case. Recovering a classical causal picture of quantum correlations thus requires an even more radical modification of our classical notion of cause and effect.

  16. Systematically convergent basis sets with relativistic pseudopotentials. II. Small-core pseudopotentials and correlation consistent basis sets for the post-d group 16-18 elements

    SciTech Connect

    Peterson, Kirk A.; Figgen, Detlev; Goll, Erich; Stoll, Hermann; Dolg, Michael F.

    2003-12-01

    Series of correlation consistent basis sets have been developed for the post-d group 16-18 elements in conjunction with small-core relativistic pseudopotentials (PPs) of the energy-consistent variety. The latter were adjusted to multiconfiguration Dirac-Hartree-Fock data based on the Dirac-Coulomb-Breit Hamiltonian. The outer-core (n-1)spd shells are explicitly treated together with the nsp valence shell with these PPs. The accompanying cc-pVnZ-PP and aug-cc-pVnZ-PP basis sets range in size from DZ to 5Z quality and yield systematic convergence of both Hartree-Fock and correlated total energies. In addition to the calculation of atomic electron affinities and dipole polarizabilities of the rare gas atoms, numerous molecular benchmark calculations (HBr, HI, HAt, Br2, I2, At2, SiSe, SiTe, SiPo, KrH+, XeH+, and RnH+) are also reported at the coupled cluster level of theory. For the purposes of comparison, all-electron calculations using the Douglas-Kroll-Hess Hamiltonian have also been carried out for the halogen-containing molecules using basis sets of 5Z quality.

  17. Dispersive shock waves with nonlocal nonlinearity.

    PubMed

    Barsi, Christopher; Wan, Wenjie; Sun, Can; Fleischer, Jason W

    2007-10-15

    We consider dispersive optical shock waves in nonlocal nonlinear media. Experiments are performed using spatial beams in a thermal liquid cell, and results agree with a hydrodynamic theory of propagation.

  18. Nonlocal ordinary magnetoresistance in indium arsenide

    NASA Astrophysics Data System (ADS)

    Liu, Pan.; Yuan, Zhonghui.; Wu, Hao.; Ali, S. S.; Wan, Caihua.; Ban, Shiliang.

    2015-07-01

    Deflection of carriers by Lorentz force results in an ordinary magnetoresistance (OMR) of (μB)2 at low field. Here we demonstrate that the OMR in high mobility semiconductor InAs could be enhanced by measurement geometry where two probes of voltmeter were both placed on one outer side of two probes of current source. The nonlocal OMR was 3.6 times as large as the local one, reaching 1.8×104% at 5 T. The slope of the linear field dependence of the nonlocal OMR was improved from 12.6 T-1 to 45.3 T-1. The improvement was ascribed to polarity-conserved charges accumulating on boundaries in nonlocal region due to Hall effect. This InAs device with nonlocal geometry could be competitive in B-sensors due to its high OMR ratio, linear field dependence and simple structure.

  19. Symmetric states: Their nonlocality and entanglement

    SciTech Connect

    Wang, Zizhu; Markham, Damian

    2014-12-04

    The nonlocality of permutation symmetric states of qubits is shown via an extension of the Hardy paradox and the extension of the associated inequality. This is achieved by using the Majorana representation, which is also a powerful tool in the study of entanglement properties of symmetric states. Through the Majorana representation, different nonlocal properties can be linked to different entanglement properties of a state, which is useful in determining the usefulness of different states in different quantum information processing tasks.

  20. Structure of quantum and broadcasting nonlocal correlations

    NASA Astrophysics Data System (ADS)

    Saha, Debashis; Pawłowski, Marcin

    2015-12-01

    The multipartite setting offers much more complexity of nonlocality than the bipartite one. We analyze the structure of tripartite nonlocal correlations by proposing inequalities satisfied by each of type bilocal, broadcasting, and quantum but violated by the other two. One of the inequalities satisfied by broadcasting correlations is generalized for multipartite systems. The study of its quantum mechanical violation reveals that Greenberger-Horne-Zeilinger-like states exhibit new, powerful correlations.

  1. Memory in a Nonlocally Damped Oscillator

    NASA Astrophysics Data System (ADS)

    Chruściński, D.; Jurkowski, J.

    2010-01-01

    We analyze the new equation of motion for the damped oscillator. It differs from the standard one by a damping term which is nonlocal in time and hence it gives rise to a system with memory. Both classical and quantum analysis is performed. The characteristic feature of this nonlocal system is that it breaks local composition low for the classical Hamiltonian dynamics and the corresponding quantum propagator.

  2. Chaotic Orbits for Systems of Nonlocal Equations

    NASA Astrophysics Data System (ADS)

    Dipierro, Serena; Patrizi, Stefania; Valdinoci, Enrico

    2016-07-01

    We consider a system of nonlocal equations driven by a perturbed periodic potential. We construct multibump solutions that connect one integer point to another one in a prescribed way. In particular, heteroclinic, homoclinic and chaotic trajectories are constructed. This is the first attempt to consider a nonlocal version of this type of dynamical systems in a variational setting and the first result regarding symbolic dynamics in a fractional framework.

  3. Nonsmooth feedback controls of nonlocal dispersal models

    NASA Astrophysics Data System (ADS)

    Malaguti, Luisa; Rubbioni, Paola

    2016-03-01

    The paper deals with a nonlocal diffusion equation which is a model for biological invasion and disease spread. A nonsmooth feedback control term is included and the existence of controlled dynamics is proved, satisfying different kinds of nonlocal condition. Jump discontinuities appear in the process. The existence of optimal control strategies is also shown, under suitably regular control functionals. The investigation makes use of techniques of multivalued analysis and is based on the degree theory for condensing operators in Hilbert spaces.

  4. The relationship between specific absorption rate and temperature elevation in anatomically based human body models for plane wave exposure from 30 MHz to 6 GHz.

    PubMed

    Hirata, Akimasa; Laakso, Ilkka; Oizumi, Takuya; Hanatani, Ryuto; Chan, Kwok Hung; Wiart, Joe

    2013-02-21

    According to the international safety guidelines/standard, the whole-body-averaged specific absorption rate (Poljak et al 2003 IEEE Trans. Electromagn. Compat. 45 141-5) and the peak spatial average SAR are used as metrics for human protection from whole-body and localized exposures, respectively. The IEEE standard (IEEE 2006 IEEE C95.1) indicates that the upper boundary frequency, over which the whole-body-averaged SAR is deemed to be the basic restriction, has been reduced from 6 to 3 GHz, because radio-wave energy is absorbed around the body surface when the frequency is increased. However, no quantitative discussion has been provided to support this description especially from the standpoint of temperature elevation. It is of interest to investigate the maximum temperature elevation in addition to the core temperature even for a whole-body exposure. In the present study, using anatomically based human models, we computed the SAR and the temperature elevation for a plane-wave exposure from 30 MHz to 6 GHz, taking into account the thermoregulatory response. As the primary result, we found that the ratio of the core temperature elevation to the whole-body-averaged SAR is almost frequency independent for frequencies below a few gigahertz; the ratio decreases above this frequency. At frequencies higher than a few gigahertz, core temperature elevation for the same whole-body averaged SAR becomes lower due to heat convection from the skin to air. This lower core temperature elevation is attributable to skin temperature elevation caused by the power absorption around the body surface. Then, core temperature elevation even for whole-body averaged SAR of 4 W kg(-1) with the duration of 1 h was at most 0.8 °C, which is smaller than a threshold considered in the safety guidelines/standard. Further, the peak 10 g averaged SAR is correlated with the maximum body temperature elevations without extremities and pinna over the frequencies considered. These findings

  5. Effects of nonlocality on transfer reactions

    NASA Astrophysics Data System (ADS)

    Titus, Luke

    Nuclear reactions play a key role in the study of nuclei away from stability. Single-nucleon transfer reactions involving deuterons provide an exceptional tool to study the single-particle structure of nuclei. Theoretically, these reactions are attractive as they can be cast into a three-body problem composed of a neutron, proton, and the target nucleus. Optical potentials are a common ingredient in reactions studies. Traditionally, nucleon-nucleus optical potentials are made local for convenience. The effects of nonlocal potentials have historically been included approximately by applying a correction factor to the solution of the corresponding equation for the local equivalent interaction. This is usually referred to as the Perey correction factor. In this thesis, we have systematically investigated the effects of nonlocality on (p,d) and (d,p) transfer reactions, and the validity of the Perey correction factor. We implemented a method to solve the single channel nonlocal equation for both bound and scattering states. We also developed an improved formalism for nonlocal interactions that includes deuteron breakup in transfer reactions. This new formalism, the nonlocal adiabatic distorted wave approximation, was used to study the effects of including nonlocality consistently in ( d,p) transfer reactions. For the (p,d) transfer reactions, we solved the nonlocal scattering and bound state equations using the Perey-Buck type interaction, and compared to local equivalent calculations. Using the distorted wave Born approximation we construct the T-matrix for (p,d) transfer on 17O, 41Ca, 49Ca, 127 Sn, 133Sn, and 209Pb at 20 and 50 MeV. Additionally we studied (p,d) reactions on 40Ca using the the nonlocal dispersive optical model. We have also included nonlocality consistently into the adiabatic distorted wave approximation and have investigated the effects of nonlocality on on (d,p) transfer reactions for deuterons impinged on 16O, 40Ca, 48Ca, 126Sn, 132Sn, 208Pb at 10

  6. On the pseudopotential approximation in the van der Waals density functional calculations

    NASA Astrophysics Data System (ADS)

    Hamada, Ikutaro; Callsen, Martin

    The van der Waals density functional (vdW-DF) is a density functional that is able to describe van der Waals and covalent interactions in a seamless fashion, and has been applied to a variety of systems. In practical calculations, the pseudopotential (PP) approximation has been employed, for which the PPs should be generated consistently for the chosen exchange correlation XC functional. However, usually PPs generated with a generalized gradient approximation (GGA) XC functional are used and the effect of the approximation to the XC functional applied in the PP generation is scarcely discussed. In this work, we discuss the appropriate XC functionals in the PP generation for the vdW-DF calculations. Furthermore, we compare the vdW-DF results for several systems using the PP's generated with appropriate XC and those with GGA XC.

  7. On the performance of energy-consistent spin orbit pseudopotentials: (111)H revisited

    NASA Astrophysics Data System (ADS)

    Dolg, Michael; Stoll, Hermann; Seth, Michael; Schwerdtfeger, Peter

    2001-09-01

    A new two-component relativistic pseudopotential (PP) of the energy-consistent (EC) variety, adjusted to multi-configuration Dirac-Hartree-Fock (MCDHF) data, is presented for the superheavy element 111 and is applied in correlated valence ab initio calculations, with and without inclusion of spin-orbit (SO) coupling, to the determination of spectroscopic constants of the element 111 monohydride. Good agreement with a recent study by Han and Hirao [Chem. Phys. Lett. 328 (2000) 453] is found, and it is concluded that a direct two-component PP fit is superior to a previously practiced two-step (scalar-relativistic/SO) adjustment procedure. We estimate the molecular constants of element 111 monohydride to be Re=1.529 Å, D e=2.83 eV and ω e=2642 cm-1.

  8. Excited calculations of large scale multiwalled nanotubes using real-space pseudopotential methods

    NASA Astrophysics Data System (ADS)

    Lena, Charles; Chelikowsky, James; Deslippe, Jack; Saad, Yousef; Yang, Chao; Louie, Steven G.

    2015-03-01

    One method for calculating excited states is the GW method. The GW method has many computational requirements. One of the bottlenecks is the calculation of numerous empty states. Within density functional theory, we use a real-space pseudopotential method (PARSEC) to calculate these empty states for multiwalled nanotubes. We illustrate the use of these empty states for calculating excited states using the GW method (BerkeleyGW). We demonstrate why using real-space density functional theory is advantageous for calculating empty states. Support provided by the SciDAC program, Department of Energy, Office of Science, Advanced Scientific Computing Research and Basic Energy Sciences. Grant Numbers DE-SC0008877 (Austin) and DE-FG02-12ER4 (Berkeley)

  9. Four-component superlattice empirical pseudopotential method for InAs/GaSb superlattices

    NASA Astrophysics Data System (ADS)

    Masur, J.-M.; Rehm, R.; Schmitz, J.; Kirste, L.; Walther, M.

    2013-11-01

    For the design of InAs/GaSb superlattice (SL) heterojunction infrared photodetectors with very low dark current we have extended the standard two-component superlattice empirical pseudopotential method (SEPM) and implemented a four-component model including interface layers. For both models, the calculated bandgap values for a set of SL samples are compared to bandgaps determined by photoluminescence measurements. While the bandgap resulting from the two-component model agrees well with experimental data for SL structures with individual layer thicknesses of 7 monolayers and more, we show that for SLs with thinner GaSb layers the four-component SEPM model is accurate, when the As-content in the interface and barrier layers is included in the model.

  10. Nonlocality in deuteron stripping reactions.

    PubMed

    Timofeyuk, N K; Johnson, R C

    2013-03-15

    We propose a new method for the analysis of deuteron stripping reactions, A(d,p)B, in which the nonlocality of nucleon-nucleus interactions and three-body degrees of freedom are accounted for in a consistent way. The model deals with equivalent local nucleon potentials taken at an energy shifted by ∼40  MeV from the "E(d)/2" value frequently used in the analysis of experimental data, where E(d) is the incident deuteron energy. The "E(d)/2" rule lies at the heart of all three-body analyses of (d, p) reactions performed so far with the aim of obtaining nuclear structure properties such as spectroscopic factors and asymptotic normalization coefficients that are crucial for our understanding of nuclear shell evolution in neutron- and proton-rich regions of the nuclear periodic table and for predicting the cross sections of stellar reactions. The large predicted shift arises from the large relative kinetic energy of the neutron and proton in the incident deuteron in those components of the n+p+A wave function that dominate the (d, p) reaction amplitude. The large shift reduces the effective d-A potentials and leads to a change in predicted (d, p) cross sections, thus affecting the interpretation of these reactions in terms of nuclear structure. PMID:25166525

  11. Effects of d-electrons in pseudopotential screened-exchange density functional calculations

    SciTech Connect

    Lee, Byounghak; Canning, Andrew; Wang, Lin-Wang

    2007-09-12

    We report a theoretical study on the role of shallow d states in the screened-exchange local density approximation (sX-LDA) band structure of binary semiconductor systems.We found that inaccurate pseudo-wavefunctions can lead to 1) an overestimation of the screened-exchange interaction betweenthe localized d states and the delocalized higher energy s and p states and 2) an underestimation of the screened-exchange interaction between the d states. The resulting sX-LDA band structures have substantially smaller band gaps compared with experiments. We correct the pseudo-wavefunctions of d states by including the semicore s and p states of the same shell in the valence states. The correction of pseudo-wavefunctions yields band gaps and d state binding energies in good agreement with experiments and the full potential linearized augmented plane wave sX-LDA calculations. Compared with the quasi-particle GW method, our sX-LDA results shows not only similar quality on the band gaps but also much better d state binding energies. Combined with its capability of ground state structure calculation, the sX-LDA is expected to be a valuable theoretical tool for the II-VI and III-V (especially the III-N) bulk semiconductors and nanostructure studies.

  12. Effects of d-electrons in pseudopotential screened-exchange density functional calculations

    NASA Astrophysics Data System (ADS)

    Lee, Byounghak; Wang, Lin-Wang; Canning, Andrew

    2008-06-01

    We report a theoretical study on the role of shallow d states in the screened-exchange local density approximation (sX-LDA) band structure of binary semiconductor systems. We found that inaccurate pseudo-wave functions can lead to (1) an overestimation of the screened-exchange interaction between the localized d states and the delocalized higher energy s and p states, and (2) an underestimation of the screened-exchange interaction between the d states. The resulting sX-LDA band structures have substantially smaller band gaps compared with experiments. We correct the pseudo-wave functions of d states by including the semicore s and p states of the same shell in the valence states. The correction of pseudo-wave functions yields band gaps and d-state binding energies in good agreement with experiments and the full potential linearized augmented plane wave sX-LDA calculations. Compared with the quasiparticle GW method, our sX-LDA results shows not only similar quality on the band gaps but also much better d-state binding energies. Combined with its capability of ground-state structure calculation, the sX-LDA is expected to be a valuable theoretical tool for the II-VI and III-V (especially the III-N) bulk semiconductors and nanostructure studies.

  13. Maximally Nonlocal Theories Cannot Be Maximally Random

    NASA Astrophysics Data System (ADS)

    de la Torre, Gonzalo; Hoban, Matty J.; Dhara, Chirag; Prettico, Giuseppe; Acín, Antonio

    2015-04-01

    Correlations that violate a Bell inequality are said to be nonlocal; i.e., they do not admit a local and deterministic explanation. Great effort has been devoted to study how the amount of nonlocality (as measured by a Bell inequality violation) serves to quantify the amount of randomness present in observed correlations. In this work we reverse this research program and ask what do the randomness certification capabilities of a theory tell us about the nonlocality of that theory. We find that, contrary to initial intuition, maximal randomness certification cannot occur in maximally nonlocal theories. We go on and show that quantum theory, in contrast, permits certification of maximal randomness in all dichotomic scenarios. We hence pose the question of whether quantum theory is optimal for randomness; i.e., is it the most nonlocal theory that allows maximal randomness certification? We answer this question in the negative by identifying a larger-than-quantum set of correlations capable of this feat. Not only are these results relevant to understanding quantum mechanics' fundamental features, but also put fundamental restrictions on device-independent protocols based on the no-signaling principle.

  14. Maximally nonlocal theories cannot be maximally random.

    PubMed

    de la Torre, Gonzalo; Hoban, Matty J; Dhara, Chirag; Prettico, Giuseppe; Acín, Antonio

    2015-04-24

    Correlations that violate a Bell inequality are said to be nonlocal; i.e., they do not admit a local and deterministic explanation. Great effort has been devoted to study how the amount of nonlocality (as measured by a Bell inequality violation) serves to quantify the amount of randomness present in observed correlations. In this work we reverse this research program and ask what do the randomness certification capabilities of a theory tell us about the nonlocality of that theory. We find that, contrary to initial intuition, maximal randomness certification cannot occur in maximally nonlocal theories. We go on and show that quantum theory, in contrast, permits certification of maximal randomness in all dichotomic scenarios. We hence pose the question of whether quantum theory is optimal for randomness; i.e., is it the most nonlocal theory that allows maximal randomness certification? We answer this question in the negative by identifying a larger-than-quantum set of correlations capable of this feat. Not only are these results relevant to understanding quantum mechanics' fundamental features, but also put fundamental restrictions on device-independent protocols based on the no-signaling principle. PMID:25955039

  15. Nonlocal Markovian models for image denoising

    NASA Astrophysics Data System (ADS)

    Salvadeo, Denis H. P.; Mascarenhas, Nelson D. A.; Levada, Alexandre L. M.

    2016-01-01

    Currently, the state-of-the art methods for image denoising are patch-based approaches. Redundant information present in nonlocal regions (patches) of the image is considered for better image modeling, resulting in an improved quality of filtering. In this respect, nonlocal Markov random field (MRF) models are proposed by redefining the energy functions of classical MRF models to adopt a nonlocal approach. With the new energy functions, the pairwise pixel interaction is weighted according to the similarities between the patches corresponding to each pair. Also, a maximum pseudolikelihood estimation of the spatial dependency parameter (β) for these models is presented here. For evaluating this proposal, these models are used as an a priori model in a maximum a posteriori estimation to denoise additive white Gaussian noise in images. Finally, results display a notable improvement in both quantitative and qualitative terms in comparison with the local MRFs.

  16. Transfer reaction code with nonlocal interactions

    NASA Astrophysics Data System (ADS)

    Titus, L. J.; Ross, A.; Nunes, F. M.

    2016-10-01

    We present a suite of codes (NLAT for nonlocal adiabatic transfer) to calculate the transfer cross section for single-nucleon transfer reactions, (d , N) or (N , d) , including nonlocal nucleon-target interactions, within the adiabatic distorted wave approximation. For this purpose, we implement an iterative method for solving the second order nonlocal differential equation, for both scattering and bound states. The final observables that can be obtained with NLAT are differential angular distributions for the cross sections of A(d , N) B or B(N , d) A. Details on the implementation of the T-matrix to obtain the final cross sections within the adiabatic distorted wave approximation method are also provided. This code is suitable to be applied for deuteron induced reactions in the range of Ed =10-70 MeV, and provides cross sections with 4% accuracy.

  17. Effectively nonlocal metric-affine gravity

    NASA Astrophysics Data System (ADS)

    Golovnev, Alexey; Koivisto, Tomi; Sandstad, Marit

    2016-03-01

    In metric-affine theories of gravity such as the C-theories, the spacetime connection is associated to a metric that is nontrivially related to the physical metric. In this article, such theories are rewritten in terms of a single metric, and it is shown that they can be recast as effectively nonlocal gravity. With some assumptions, known ghost-free theories with nonsingular and cosmologically interesting properties may be recovered. Relations between different formulations are analyzed at both perturbative and nonperturbative levels, taking carefully into account subtleties with boundary conditions in the presence of integral operators in the action, and equivalences between theories related by nonlocal redefinitions of the fields are verified at the level of equations of motion. This suggests a possible geometrical interpretation of nonlocal gravity as an emergent property of non-Riemannian spacetime structure.

  18. Nonlocal spin correlations mediated by a superconductor

    NASA Astrophysics Data System (ADS)

    Noh, Taewan; Houzet, Manuel; Meyer, Julia S.; Chandrasekhar, Venkat

    2013-06-01

    Nonlocal charge correlations induced in two normal metals contacted separately to a superconductor have been studied intensively in the past few years. Here we investigate nonlocal correlations induced by the transfer of pure spin currents through a superconductor on a scale comparable to the superconducting coherence length. As with charge currents, two processes contribute to the nonlocal spin signal: crossed Andreev reflection (CAR), where an electron with spin-up injected from one normal metal into the superconductor results in a hole with spin-down being injected into the second normal metal, and elastic cotunneling (EC), where the electron with spin-up injected from the first normal metal results in an electron with spin-up being injected into the second normal metal. Unlike charge currents, however, the spin currents associated with CAR and EC add due to the fact that the bulk superconductor cannot sustain a net spin current.

  19. Hardy's criterion of nonlocality for mixed states

    SciTech Connect

    Ghirardi, GianCarlo; Marinatto, Luca

    2006-03-15

    We generalize Hardy's proof of nonlocality to the case of bipartite mixed statistical operators, and we exhibit a necessary condition which has to be satisfied by any given mixed state {sigma} in order that a local and realistic hidden variable model exists which accounts for the quantum mechanical predictions implied by {sigma}. Failure of this condition will imply both the impossibility of any local explanation of certain joint probability distributions in terms of hidden variables and the nonseparability of the considered mixed statistical operator. Our result can be also used to determine the maximum amount of noise, arising from imperfect experimental implementations of the original Hardy's proof of nonlocality, in presence of which it is still possible to put into evidence the nonlocal features of certain mixed states.

  20. Nonlocal spectroscopy of Andreev bound states

    NASA Astrophysics Data System (ADS)

    Schindele, J.; Baumgartner, A.; Maurand, R.; Weiss, M.; Schönenberger, C.

    2014-01-01

    We experimentally investigate Andreev bound states (ABSs) in a carbon nanotube quantum dot (QD) connected to a superconducting Nb lead (S). A weakly coupled normal metal contact acts as a tunnel probe that measures the energy dispersion of the ABSs. Moreover, we study the response of the ABS to nonlocal transport processes, namely, Cooper pair splitting and elastic co-tunnelling, which are enabled by a second QD fabricated on the same nanotube on the opposite side of S. We find an appreciable nonlocal conductance with a rich structure, including a sign reversal at the ground-state transition from the ABS singlet to a degenerate magnetic doublet. We describe our device by a simple rate equation model that captures the key features of our observations and demonstrates that the sign of the nonlocal conductance is a measure for the charge distribution of the ABS, given by the respective Bogoliubov-de Gennes amplitudes u and v.

  1. Reversed rainbow with a nonlocal metamaterial

    SciTech Connect

    Morgado, Tiago A. Marcos, João S.; Silveirinha, Mário G.; Costa, João T.; Costa, Jorge R.; Fernandes, Carlos A.

    2014-12-29

    One of the intriguing potentials of metamaterials is the possibility to realize a nonlocal electromagnetic reaction, such that the effective medium response at a given point is fundamentally entangled with the macroscopic field distribution at long distances. Here, it is experimentally and numerically verified that a microwave nonlocal metamaterial formed by crossed metallic wires enables a low-loss broadband anomalous material response such that the refractive index decreases with frequency. Notably, it is shown that an electromagnetic beam refracted by our metamaterial prism creates a reversed microwave rainbow.

  2. Experimental nonlocal and surreal Bohmian trajectories.

    PubMed

    Mahler, Dylan H; Rozema, Lee; Fisher, Kent; Vermeyden, Lydia; Resch, Kevin J; Wiseman, Howard M; Steinberg, Aephraim

    2016-02-01

    Weak measurement allows one to empirically determine a set of average trajectories for an ensemble of quantum particles. However, when two particles are entangled, the trajectories of the first particle can depend nonlocally on the position of the second particle. Moreover, the theory describing these trajectories, called Bohmian mechanics, predicts trajectories that were at first deemed "surreal" when the second particle is used to probe the position of the first particle. We entangle two photons and determine a set of Bohmian trajectories for one of them using weak measurements and postselection. We show that the trajectories seem surreal only if one ignores their manifest nonlocality.

  3. Nonlocal formulation of spin Coulomb drag

    NASA Astrophysics Data System (ADS)

    D'Amico, I.; Ullrich, C. A.

    2013-10-01

    The spin Coulomb drag (SCD) effect occurs in materials and devices where charged carriers with different spins exchange momentum via Coulomb scattering. This causes frictional forces between spin-dependent currents that lead to intrinsic dissipation, which may limit spintronics applications. A nonlocal formulation of SCD is developed which is valid for strongly inhomogeneous systems such as nanoscale spintronics devices. This nonlocal formulation of SCD is successfully applied to linewidths of intersubband spin plasmons in semiconductor quantum wells, where experiments have shown that the local approximation fails.

  4. Compressive Sensing via Nonlocal Smoothed Rank Function.

    PubMed

    Fan, Ya-Ru; Huang, Ting-Zhu; Liu, Jun; Zhao, Xi-Le

    2016-01-01

    Compressive sensing (CS) theory asserts that we can reconstruct signals and images with only a small number of samples or measurements. Recent works exploiting the nonlocal similarity have led to better results in various CS studies. To better exploit the nonlocal similarity, in this paper, we propose a non-convex smoothed rank function based model for CS image reconstruction. We also propose an efficient alternating minimization method to solve the proposed model, which reduces a difficult and coupled problem to two tractable subproblems. Experimental results have shown that the proposed method performs better than several existing state-of-the-art CS methods for image reconstruction. PMID:27583683

  5. Observational viability and stability of nonlocal cosmology

    SciTech Connect

    Deser, S.; Woodard, R.P. E-mail: woodard@phys.ufl.edu

    2013-11-01

    We show that the nonlocal gravity models, proposed to explain current cosmic acceleration without dark energy, pass two essential tests: first, they can be defined so as not to alter the, observationally correct, general relativity predictions for gravitationally bound systems. Second, they are stable, ghost-free, with no additional excitations beyond those of general relativity. In this they differ from their, ghostful, localized versions. The systems' initial value constraints are the same as in general relativity, and our nonlocal modifications never convert the original gravitons into ghosts.

  6. Experimental nonlocal and surreal Bohmian trajectories.

    PubMed

    Mahler, Dylan H; Rozema, Lee; Fisher, Kent; Vermeyden, Lydia; Resch, Kevin J; Wiseman, Howard M; Steinberg, Aephraim

    2016-02-01

    Weak measurement allows one to empirically determine a set of average trajectories for an ensemble of quantum particles. However, when two particles are entangled, the trajectories of the first particle can depend nonlocally on the position of the second particle. Moreover, the theory describing these trajectories, called Bohmian mechanics, predicts trajectories that were at first deemed "surreal" when the second particle is used to probe the position of the first particle. We entangle two photons and determine a set of Bohmian trajectories for one of them using weak measurements and postselection. We show that the trajectories seem surreal only if one ignores their manifest nonlocality. PMID:26989784

  7. Experimental nonlocal and surreal Bohmian trajectories

    PubMed Central

    Mahler, Dylan H.; Rozema, Lee; Fisher, Kent; Vermeyden, Lydia; Resch, Kevin J.; Wiseman, Howard M.; Steinberg, Aephraim

    2016-01-01

    Weak measurement allows one to empirically determine a set of average trajectories for an ensemble of quantum particles. However, when two particles are entangled, the trajectories of the first particle can depend nonlocally on the position of the second particle. Moreover, the theory describing these trajectories, called Bohmian mechanics, predicts trajectories that were at first deemed “surreal” when the second particle is used to probe the position of the first particle. We entangle two photons and determine a set of Bohmian trajectories for one of them using weak measurements and postselection. We show that the trajectories seem surreal only if one ignores their manifest nonlocality. PMID:26989784

  8. Compressive Sensing via Nonlocal Smoothed Rank Function

    PubMed Central

    Fan, Ya-Ru; Liu, Jun; Zhao, Xi-Le

    2016-01-01

    Compressive sensing (CS) theory asserts that we can reconstruct signals and images with only a small number of samples or measurements. Recent works exploiting the nonlocal similarity have led to better results in various CS studies. To better exploit the nonlocal similarity, in this paper, we propose a non-convex smoothed rank function based model for CS image reconstruction. We also propose an efficient alternating minimization method to solve the proposed model, which reduces a difficult and coupled problem to two tractable subproblems. Experimental results have shown that the proposed method performs better than several existing state-of-the-art CS methods for image reconstruction. PMID:27583683

  9. Low energy signatures of nonlocal field theories

    NASA Astrophysics Data System (ADS)

    Belenchia, Alessio; Benincasa, Dionigi M. T.; Martín-Martínez, Eduardo; Saravani, Mehdi

    2016-09-01

    The response of inertial particle detectors coupled to a scalar field satisfying nonlocal dynamics described by nonanalytic functions of the d'Alembertian operator □ is studied. We show that spontaneous emission processes of a low energy particle detector are very sensitive to high-energy nonlocality scales. This allows us to suggest a nuclear physics experiment (˜MeV energy scales) that outperforms the sensitivity of LHC experiments by many orders of magnitude. This may have implications for the falsifiability of theoretical proposals of quantum gravity.

  10. Compressive Sensing via Nonlocal Smoothed Rank Function.

    PubMed

    Fan, Ya-Ru; Huang, Ting-Zhu; Liu, Jun; Zhao, Xi-Le

    2016-01-01

    Compressive sensing (CS) theory asserts that we can reconstruct signals and images with only a small number of samples or measurements. Recent works exploiting the nonlocal similarity have led to better results in various CS studies. To better exploit the nonlocal similarity, in this paper, we propose a non-convex smoothed rank function based model for CS image reconstruction. We also propose an efficient alternating minimization method to solve the proposed model, which reduces a difficult and coupled problem to two tractable subproblems. Experimental results have shown that the proposed method performs better than several existing state-of-the-art CS methods for image reconstruction.

  11. Non-locality Sudden Death in Tripartite Systems

    SciTech Connect

    Jaeger, Gregg; Ann, Kevin

    2009-03-10

    Bell non-locality sudden death is the disappearance of non-local properties in finite times under local phase noise, which decoheres states only in the infinite-time limit. We consider the relationship between decoherence, disentanglement, and Bell non-locality sudden death in bipartite and tripartite systems in specific large classes of state preparation.

  12. Quantum transport and dielectric response of nanometer scale transistors using empirical pseudopotentials

    NASA Astrophysics Data System (ADS)

    Fang, Jingtian

    As transistors, the most basic component of central processing units (CPU) in all electronic products, are scaling down to the nanometer scale, quantum mechanical effects must be studied to investigate their performance. A formalism to treat quantum electronic transport at the nanometer scale based on empirical pseudopotentials is presented in this dissertation. We develop the transport equations and show the expressions to calculate the device characteristics, such as device current and charge density. We apply this formalism to study ballistic transport in a gate-all-around (GAA) silicon nanowire field-effect transistor (FET) with a body-size of 0.39 nm, a gate length of 6.52 nm, and an effective oxide thickness of 0.43 nm. Simulation results show that this device exhibits a subthreshold slope (SS) of ˜66 mV/decade and a drain-induced barrier-lowering of ~2.5 mV/V. This formalism is also applied to assess the ballistic performance of FETs with armchair-edge graphene nanoribbon (aGNRs) and silicon nanowire (SiNWs) channels and with gate lengths ranging from 5 nm to 15 nm. The device characteristics of the transistors with a 5 nm gate length are compared. Source-to-drain tunneling effects are investigated for SiNWFETs and GNRFETs by comparing the I-V characteristics of each respective transistor with different channel lengths. While a uniform dielectric constant is assumed in solving Poisson equation for the devices simulated above, the knowledge of the atomistic (i.e., local) dielectric permittivity that considers the atomistic electron distribution and quantum-confinement effect is necessary to treat the electrostatic properties accurately. The local permittivity can also provide information about the dielectric property at the interfaces. We use the random-phase approximation, first-order perturbation theory, and empirical pseudopotentials to calculate the static polarizability, susceptibility, and dielectric response function in graphene and GNRs. While the

  13. Pseudopotential calculations and photothermal lensing measurements of two-photon absorption in solids

    SciTech Connect

    White, W.T. III

    1985-11-04

    We have studied two-photon absorption in solids theoretically and experimentally. We have shown that it is possible to use accurate band structure techniques to compute two-photon absorption spectra within 15% of measured values in a wide band-gap material, ZnS. The empirical pseudopotential technique that we used is significantly more accurate than previous models of two-photon absorption in zinc blende materials, including present tunneling theories (which are essentially parabolic-band results in disguise) and the nonparabolic-band formalism of Pidgeon et al. and Weiler. The agreement between our predictions and previous measurements allowed us to use ZnS as a reference material in order to validate a technique for measuring two-photon absorption that was previously untried in solids, pulsed dual-beam thermal lensing. With the validated technique, we examined nonlinear absorption in one other crystal (rutile) and in several glasses, including silicates, borosilicates, and one phosphate glass. Initially, we believed that the absorption edges of all the materials were comparable; however, subsequent evidence suggested that the effective band-gap energies of the glasses were above the energy of two photons in our measurement. Therefore, we attribute the nonlinear absorption that we observed in glasses to impurities or defects. The measured nonlinear absorption coefficients were of the order of a few cm/TW in the glasses and of the order of 10 cm/GW in the crystals, four orders of magnitude higher than in glasses. 292 refs.

  14. The temperature-dependent electrical transport properties of liquid Sn using pseudopotential theory

    NASA Astrophysics Data System (ADS)

    Patel, A. B.; Bhatt, N. K.; Thakore, B. Y.; Vyas, P. R.; Jani, A. R.

    2014-08-01

    We present the calculations of electrical resistivity, thermo-electric power and thermal conductivity based on the self-consistent approximation. The pseudopotential due to Hasegawa et al. [J. Non-Cryst. Solids 117/118, 300 (1990)] for full electron-ion interaction, which is valid for all electrons and contains the repulsive delta function to achieve the necessary s-pseudisation, was used in the calculation. Temperature dependence of structure factor is achieved through temperature-dependent potential parameter in the pair-potential. The outcome of the present study is discussed in the light of other such results and with predictions of Wiedemann and Franz law up to moderately high temperature. Specially, high-temperature resistivity data necessitates the careful investigation of electron energy dispersion close to the Fermi level and possible metal to non-metal transition while going from dense-fluid to low density-fluid state. In the absence of experimental data at high temperature, these findings may serve as future guideline.

  15. Describing the Hydrated Electron with a Polarizable Electron-Water Pseudopotential

    NASA Astrophysics Data System (ADS)

    Jacobson, Leif D.; Herbert, John M.

    2010-06-01

    We have constructed a one-electron pseudopotential that treats the mutual polarization of an excess electron with a water bath in a self-consistent fashion. This potential is able to reproduce MP2-quality vertical binding energies of anionic water clusters with an average error of less than 0.1 eV. We are also able to reproduce the bulk optical absorption spectrum of the aqueous electron where we find that the many-electron response of the water bath is important in describing the lineshape of this spectrum. The binding energy and absorption spectrum maximum have been important experimental observables in studies of anionic water clusters and so our potential is well suited to address the structural complexity of these systems. We reconstruct a diagram of vertical binding energy versus inverse cluster size in order to investigate the extent to which our model is able to reproduce photoelectron experimental data for anionic water clusters for n=20-200, as well as provide insight into the binding motifs of these clusters.

  16. Measuring the Quality of Generalized Gradient Approximations in a Density Functional Theory Pseudopotential Environment for Solids

    NASA Astrophysics Data System (ADS)

    Nault, Zachary; Cancio, Antonio

    2013-03-01

    Much recent development in DFT has focused on improving GGAs. Two schemes are second order GGA (SOGGA) and the APBE which builds the GGA from atomic systems and not the HEG. Both of these have been tested within an all electron (AE) environment, providing the most accurate results. The focus of many simulations, however, is on large systems using pseudopotentials (PsP's). Are these PsP calculations, which rely on functionals tested in an AE environment, accurately reproducing the AE ground state properties? If not, can the deficiencies be identified? To assess this, we use the PsP generator APE, using the functional library libXC which works with the PsP package ABINIT and the AE package Elk. We generate standard Troullier-Martin PsP's based on common and new XC functionals (LDA, PBE, PBEsol, APBE, SOGGA) and test their performance in 13 solids (Na, Li, Al, C, Si, GaAs, NaCl, LiF, LiCl, Cu, Pd, Rh, and Ag). We measure how well three ground state properties (lattice constant, bulk modulus, and cohesive energy) are calculated with PsP's as compared to the corresponding AE calculations.

  17. Ultrasoft pseudopotentials and projector augmented-wave data sets: application to diatomic molecules

    NASA Astrophysics Data System (ADS)

    Adllan, Alwaleed Ahmed; Dal Corso, Andrea

    2011-10-01

    We test several ultrasoft pseudopotentials (US-PPs) and projector augmented-wave (PAW) data sets, calculating the bond lengths, the atomization energies and the frequencies of the vibrational stretch modes of various diatomic molecules. The US-PPs and the PAW data sets are constructed with the same recipe and using the local density approximation or the Perdew, Burke and Ernzerhof generalized gradient approximation for the exchange and correlation energies. We study the dimers H2, N2, O2, F2, Al2, Si2, P2, S2 and Cl2 and several monohydrides, carbides, nitrides and oxides of boron, carbon, nitrogen, oxygen, fluorine, aluminum, silicon, phosphorus, sulfur, chlorine, iron and nickel. We find that US-PPs and PAW data sets constructed with the same parameters provide almost equivalent results for the bond lengths and the vibrational stretch frequencies while, for some molecules, the PAW method is superior to the US-PP method for the calculation of the atomization energies. Our geometries and vibrational frequencies are compared with the results present in the literature and obtained by localized basis sets. It is found that the agreement is very good, with discrepancies comparable to those due to the use of different localized basis sets.

  18. Contact angle adjustment in equation-of-state-based pseudopotential model.

    PubMed

    Hu, Anjie; Li, Longjian; Uddin, Rizwan; Liu, Dong

    2016-05-01

    The single component pseudopotential lattice Boltzmann model has been widely applied in multiphase simulation due to its simplicity and stability. In many studies, it has been claimed that this model can be stable for density ratios larger than 1000. However, the application of the model is still limited to small density ratios when the contact angle is considered. The reason is that the original contact angle adjustment method influences the stability of the model. Moreover, simulation results in the present work show that, by applying the original contact angle adjustment method, the density distribution near the wall is artificially changed, and the contact angle is dependent on the surface tension. Hence, it is very inconvenient to apply this method with a fixed contact angle, and the accuracy of the model cannot be guaranteed. To solve these problems, a contact angle adjustment method based on the geometry analysis is proposed and numerically compared with the original method. Simulation results show that, with our contact angle adjustment method, the stability of the model is highly improved when the density ratio is relatively large, and it is independent of the surface tension. PMID:27301005

  19. Energy-consistent relativistic pseudopotentials and correlation consistent basis sets for the 4d elements Y-Pd

    NASA Astrophysics Data System (ADS)

    Peterson, Kirk A.; Figgen, Detlev; Dolg, Michael; Stoll, Hermann

    2007-03-01

    Scalar-relativistic pseudopotentials and corresponding spin-orbit potentials of the energy-consistent variety have been adjusted for the simulation of the [Ar]3d10 cores of the 4d transition metal elements Y-Pd. These potentials have been determined in a one-step procedure using numerical two-component calculations so as to reproduce atomic valence spectra from four-component all-electron calculations. The latter have been performed at the multi-configuration Dirac-Hartree-Fock level, using the Dirac-Coulomb Hamiltonian and perturbatively including the Breit interaction. The derived pseudopotentials reproduce the all-electron reference data with an average accuracy of 0.03eV for configurational averages over nonrelativistic orbital configurations and 0.1eV for individual relativistic states. Basis sets following a correlation consistent prescription have also been developed to accompany the new pseudopotentials. These range in size from cc-pVDZ-PP to cc-pV5Z-PP and also include sets for 4s4p correlation (cc-pwCVDZ-PP through cc-pwCV5Z-PP), as well as those with extra diffuse functions (aug-cc-pVDZ-PP, etc.). In order to accurately assess the impact of the pseudopotential approximation, all-electron basis sets of triple-zeta quality have also been developed using the Douglas-Kroll-Hess Hamiltonian (cc-pVTZ-DK, cc-pwCVTZ-DK, and aug-cc-pVTZ-DK). Benchmark calculations of atomic ionization potentials and 4dm -25s2→4dm -15s1 electronic excitation energies are reported at the coupled cluster level of theory with extrapolations to the complete basis set limit.

  20. Energy-consistent relativistic pseudopotentials and correlation consistent basis sets for the 4d elements Y-Pd.

    PubMed

    Peterson, Kirk A; Figgen, Detlev; Dolg, Michael; Stoll, Hermann

    2007-03-28

    Scalar-relativistic pseudopotentials and corresponding spin-orbit potentials of the energy-consistent variety have been adjusted for the simulation of the [Ar]3d(10) cores of the 4d transition metal elements Y-Pd. These potentials have been determined in a one-step procedure using numerical two-component calculations so as to reproduce atomic valence spectra from four-component all-electron calculations. The latter have been performed at the multi-configuration Dirac-Hartree-Fock level, using the Dirac-Coulomb Hamiltonian and perturbatively including the Breit interaction. The derived pseudopotentials reproduce the all-electron reference data with an average accuracy of 0.03 eV for configurational averages over nonrelativistic orbital configurations and 0.1 eV for individual relativistic states. Basis sets following a correlation consistent prescription have also been developed to accompany the new pseudopotentials. These range in size from cc-pVDZ-PP to cc-pV5Z-PP and also include sets for 4s4p correlation (cc-pwCVDZ-PP through cc-pwCV5Z-PP), as well as those with extra diffuse functions (aug-cc-pVDZ-PP, etc.). In order to accurately assess the impact of the pseudopotential approximation, all-electron basis sets of triple-zeta quality have also been developed using the Douglas-Kroll-Hess Hamiltonian (cc-pVTZ-DK, cc-pwCVTZ-DK, and aug-cc-pVTZ-DK). Benchmark calculations of atomic ionization potentials and 4d(m-2)5s(2)-->4d(m-1)5s(1) electronic excitation energies are reported at the coupled cluster level of theory with extrapolations to the complete basis set limit. PMID:17411102

  1. GENERAL Pseudopotentials, Lax Pairs and Bäcklund Transformations for Generalized Fifth-Order KdV Equation

    NASA Astrophysics Data System (ADS)

    Yang, Yun-Qing; Chen, Yong

    2011-01-01

    Based on the method developed by Nucci, the pseudopotentials, Lax pairs and the singularity manifold equations of the generalized fifth-order KdV equation are derived. By choosing different coefficient, the corresponding results and the Bäcklund transformations can be obtained on three conditioners which include Caudrey—Dodd—Gibbon—Sawada—Kotera equation, the Lax equation and the Kaup-kupershmidt equation.

  2. Nonlocality and entanglement via the Unruh effect

    SciTech Connect

    Tian, Zehua; Wang, Jieci; Jing, Jiliang

    2013-05-15

    Modeling the qubit by a two-level semiclassical detector coupled to a massless scalar field, we investigate how the Unruh effect affects the nonlocality and entanglement of two-qubit and three-qubit states when one of the entangled qubits is accelerated. Two distinct differences with the results of free field model in non-inertial frames are (i) for the two-qubit state, the CHSH inequality cannot be violated for sufficiently large but finite acceleration, furthermore, the concurrence will experience “sudden death”; and (ii) for the three-qubit state, not only does the entanglement vanish in the infinite acceleration limit, but also the Svetlichny inequality cannot be violated in the case of large acceleration. -- Highlights: ► We compare entanglement and nonlocality of two-level detector model with that of free field model in noninertial frame. ► Two-qubit state entanglement experiences “sudden death”. ► Three-qubit state entanglement vanishes in the infinite acceleration limit. ► Bipartite nonlocal correlations vanish for finite values of the acceleration. ► Tripartite nonlocal correlations vanish for finite values of the acceleration as well.

  3. 29 CFR 780.320 - Nonlocal minors.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... That Is Exempted From the Minimum Wage and Overtime Pay Requirements Under Section 13(a)(6) Statutory... 29 Labor 3 2012-07-01 2012-07-01 false Nonlocal minors. 780.320 Section 780.320 Labor Regulations Relating to Labor (Continued) WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR STATEMENTS OF GENERAL POLICY...

  4. 29 CFR 780.320 - Nonlocal minors.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... That Is Exempted From the Minimum Wage and Overtime Pay Requirements Under Section 13(a)(6) Statutory... 29 Labor 3 2010-07-01 2010-07-01 false Nonlocal minors. 780.320 Section 780.320 Labor Regulations Relating to Labor (Continued) WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR STATEMENTS OF GENERAL POLICY...

  5. 29 CFR 780.320 - Nonlocal minors.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... That Is Exempted From the Minimum Wage and Overtime Pay Requirements Under Section 13(a)(6) Statutory... 29 Labor 3 2011-07-01 2011-07-01 false Nonlocal minors. 780.320 Section 780.320 Labor Regulations Relating to Labor (Continued) WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR STATEMENTS OF GENERAL POLICY...

  6. 29 CFR 780.320 - Nonlocal minors.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... That Is Exempted From the Minimum Wage and Overtime Pay Requirements Under Section 13(a)(6) Statutory... 29 Labor 3 2014-07-01 2014-07-01 false Nonlocal minors. 780.320 Section 780.320 Labor Regulations Relating to Labor (Continued) WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR STATEMENTS OF GENERAL POLICY...

  7. 29 CFR 780.320 - Nonlocal minors.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... That Is Exempted From the Minimum Wage and Overtime Pay Requirements Under Section 13(a)(6) Statutory... 29 Labor 3 2013-07-01 2013-07-01 false Nonlocal minors. 780.320 Section 780.320 Labor Regulations Relating to Labor (Continued) WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR STATEMENTS OF GENERAL POLICY...

  8. Testing nonlocal realism with entangled coherent states

    SciTech Connect

    Paternostro, Mauro; Jeong, Hyunseok

    2010-03-15

    We investigate the violation of nonlocal realism using entangled coherent states (ECSs) under nonlinear operations and homodyne measurements. We address recently proposed Leggett-type inequalities, including a class of optimized incompatibility inequalities proposed by Branciard et al. [Nature Phys. 4, 681 (2008)], and thoroughly assess the effects of detection inefficiency.

  9. Strained band edge characteristics from hybrid density functional theory and empirical pseudopotentials: GaAs, GaSb, InAs and InSb

    NASA Astrophysics Data System (ADS)

    Çakan, Aslı; Sevik, Cem; Bulutay, Ceyhun

    2016-03-01

    The properties of a semiconductor are drastically modified when the crystal point group symmetry is broken under an arbitrary strain. We investigate the family of semiconductors consisting of GaAs, GaSb, InAs and InSb, considering their electronic band structure and deformation potentials subject to various strains based on hybrid density functional theory. Guided by these first-principles results, we develop strain-compliant local pseudopotentials for use in the empirical pseudopotential method (EPM). We demonstrate that the newly proposed empirical pseudopotentials perform well close to band edges and under anisotropic crystal deformations. Using the EPM, we explore the heavy hole-light hole mixing characteristics under different stress directions, which may be useful in manipulating their transport properties and optical selection rules. The very low 5 Ry cutoff targeted in the generated pseudopotentials paves the way for large-scale EPM-based electronic structure computations involving these lattice mismatched constituents.

  10. Hidden variables and nonlocality in quantum mechanics

    NASA Astrophysics Data System (ADS)

    Hemmick, Douglas Lloyd

    1997-05-01

    Most physicists hold a skeptical attitude toward a 'hidden variables' interpretation of quantum theory, despite David Bohm's successful construction of such a theory and John S. Bell's strong arguments in favor of the idea. The first reason for doubt concerns certain mathematical theorems (von Neumann's, Gleason's, Kochen and Specker's, and Bell's) which can be applied to the hidden variables issue. These theorems are often credited with proving that hidden variables are indeed 'impossible', in the sense that they cannot replicate the predictions of quantum mechanics. Many who do not draw such a strong conclusion nevertheless accept that hidden variables have been shown to exhibit prohibitively complicated features. The second concern is that the most sophisticated example of a hidden variables theory-that of David Bohm-exhibits non-locality, i.e., consequences of events at one place can propagate to other places instantaneously. However, neither the mathematical theorems in question nor the attribute of nonlocality detract from the importance of a hidden variables interpretation of quantum theory. Nonlocality is present in quantum mechanics itself, and is a required characteristic of any theory that agrees with the quantum mechanical predictions. We first discuss the earliest analysis of hidden variables-that of von Neumann's theorem-and review John S. Bell's refutation of von Neumann's 'impossibility proof'. We recall and elaborate on Bell's arguments regarding the theorems of Gleason, and Kochen and Specker. According to Bell, these latter theorems do not imply that hidden variables interpretations are untenable, but instead that such theories must exhibit contextuality, i.e., they must allow for the dependence of measurement results on the characteristics of both measured system and measuring apparatus. We demonstrate a new way to understand the implications of both Gleason's theorem and Kochen and Specker's theorem by noting that they prove a result we call

  11. Quantum mechanical simulation of electronic transport in nanostructured devices by efficient self-consistent pseudopotential calculation

    NASA Astrophysics Data System (ADS)

    Jiang, Xiang-Wei; Li, Shu-Shen; Xia, Jian-Bai; Wang, Lin-Wang

    2011-03-01

    We present a new empirical pseudopotential (EPM) calculation approach to simulate the million atom nanostructured semiconductor devices under potential bias using periodic boundary conditions. To treat the nonequilibrium condition, instead of directly calculating the scattering states from the source and drain, we calculate the stationary states by the linear combination of bulk band method and then decompose the stationary wave function into source and drain injecting scattering states according to an approximated top of the barrier splitting (TBS) scheme based on physical insight of ballistic and tunneling transports. The decomposed electronic scattering states are then occupied according to the source/drain Fermi-Levels to yield the occupied electron density which is then used to solve the potential, forming a self-consistent loop. The TBS is tested in a one-dimensional effective mass model by comparing with the direct scattering state calculation results. It is also tested in a three-dimensional 22 nm double gate ultra-thin-body field-effect transistor study, by comparing the TBS-EPM result with the nonequilibrium Green's function tight-binding result. We expected the TBS scheme will work whenever the potential in the barrier region is smoother than the wave function oscillations and it does not have local minimum, thus there is no multiple scattering as in a resonant tunneling diode, and when a three-dimensional problem can be represented as a quasi-one-dimensional problem, e.g., in a variable separation approximation. Using our approach, a million atom nonequilibrium nanostructure device can be simulated with EPM on a single processor computer.

  12. Classification of scalar and dyadic nonlocal optical response models.

    PubMed

    Wubs, M

    2015-11-30

    Nonlocal optical response is one of the emerging effects on the nanoscale for particles made of metals or doped semiconductors. Here we classify and compare both scalar and tensorial nonlocal response models. In the latter case the nonlocality can stem from either the longitudinal response, the transverse response, or both. In phenomenological scalar models the nonlocal response is described as a smearing out of the commonly assumed infinitely localized response, as characterized by a distribution with a finite width. Here we calculate explicitly whether and how tensorial models, such as the hydrodynamic Drude model and generalized nonlocal optical response theory, follow this phenomenological description. We find considerable differences, for example that nonlocal response functions, in contrast to simple distributions, assume negative and complex values. Moreover, nonlocal response regularizes some but not all diverging optical near fields. We identify the scalar model that comes closest to the hydrodynamic model. Interestingly, for the hydrodynamic Drude model we find that actually only one third (1/3) of the free-electron response is smeared out nonlocally. In that sense, nonlocal response is stronger for transverse and scalar nonlocal response models, where the smeared-out fractions are 2/3 and 3/3, respectively. The latter two models seem to predict novel plasmonic resonances also below the plasma frequency, in contrast to the hydrodynamic model that predicts standing pressure waves only above the plasma frequency. PMID:26698757

  13. Nonlocal polarization interferometer for entanglement detection

    SciTech Connect

    Williams, Brian P.; Humble, Travis S.; Grice, Warren P.

    2014-10-30

    We report a nonlocal interferometer capable of detecting entanglement and identifying Bell states statistically. This is possible due to the interferometer's unique correlation dependence on the antidiagonal elements of the density matrix, which have distinct bounds for separable states and unique values for the four Bell states. The interferometer consists of two spatially separated balanced Mach-Zehnder or Sagnac interferometers that share a polarization-entangled source. Correlations between these interferometers exhibit nonlocal interference, while single-photon interference is suppressed. This interferometer also allows for a unique version of the Clauser-Horne-Shimony-Holt Bell test where the local reality is the photon polarization. In conclusion, we present the relevant theory and experimental results.

  14. Nonlocal polarization interferometer for entanglement detection

    DOE PAGES

    Williams, Brian P.; Humble, Travis S.; Grice, Warren P.

    2014-10-30

    We report a nonlocal interferometer capable of detecting entanglement and identifying Bell states statistically. This is possible due to the interferometer's unique correlation dependence on the antidiagonal elements of the density matrix, which have distinct bounds for separable states and unique values for the four Bell states. The interferometer consists of two spatially separated balanced Mach-Zehnder or Sagnac interferometers that share a polarization-entangled source. Correlations between these interferometers exhibit nonlocal interference, while single-photon interference is suppressed. This interferometer also allows for a unique version of the Clauser-Horne-Shimony-Holt Bell test where the local reality is the photon polarization. In conclusion, wemore » present the relevant theory and experimental results.« less

  15. The link between entropic uncertainty and nonlocality

    NASA Astrophysics Data System (ADS)

    Tomamichel, Marco; Hänggi, Esther

    2013-02-01

    Two of the most intriguing features of quantum physics are the uncertainty principle and the occurrence of nonlocal correlations. The uncertainty principle states that there exist pairs of incompatible measurements on quantum systems such that their outcomes cannot both be predicted. On the other hand, nonlocal correlations of measurement outcomes at different locations cannot be explained by classical physics, but appear in the presence of entanglement. Here, we show that these two fundamental quantum effects are quantitatively related. Namely, we provide an entropic uncertainty relation for the outcomes of two binary measurements, where the lower bound on the uncertainty is quantified in terms of the maximum Clauser-Horne-Shimony-Holt value that can be achieved with these measurements. We discuss applications of this uncertainty relation in quantum cryptography, in particular, to certify quantum sources using untrusted devices.

  16. Molecular decay rate near nonlocal plasmonic particles.

    PubMed

    Girard, Christian; Cuche, Aurélien; Dujardin, Erik; Arbouet, Arnaud; Mlayah, Adnen

    2015-05-01

    When the size of metal nanoparticles is smaller than typically 10 nm, their optical response becomes sensitive to both spatial dispersion and quantum size effects associated with the confinement of the conduction electrons inside the particle. In this Letter, we propose a nonlocal scheme to compute molecular decay rates near spherical nanoparticles which includes the electron-electron interactions through a simple model of electronic polarizabilities. The plasmonic particle is schematized by a dynamic dipolar polarizability α(NL)(ω), and the quantum system is characterized by a two-level system. In this scheme, the light matter interaction is described in terms of classical field susceptibilities. This theoretical framework could be extended to address the influence of nonlocality on the dynamics of quantum systems placed in the vicinity of nano-objects of arbitrary morphologies.

  17. Giant nonlocal lossless permittivity at optical frequencies.

    PubMed

    Goncharenko, A V; Nazarov, V U

    2015-08-10

    We show how to achieve a giant permittivity combined with negligible losses in both the visible and the near-IR for composites made of alternating layers of plasmonic and gain materials as the electric field is directed normally to the layers. The effects of nonlocality are taken into account that makes the method quite realistic. Solving the dispersion equation for eigenmodes of an infinite layered composite, we show that both propagating and nonpropagating modes can be excited, that leads to the realization of a giant nonlocal permittivity. Both phase and group velocities for the propagating eigenmode have been calculated showing that slow light can be achieved in the system under study. The results obtained open new possibilities for designing nanolaser, slow-light, superresolution imaging devices, etc. PMID:26367898

  18. Sampling Quantum Nonlocal Correlations with High Probability

    NASA Astrophysics Data System (ADS)

    González-Guillén, C. E.; Jiménez, C. H.; Palazuelos, C.; Villanueva, I.

    2016-05-01

    It is well known that quantum correlations for bipartite dichotomic measurements are those of the form {γ=(< u_i,v_jrangle)_{i,j=1}^n}, where the vectors u i and v j are in the unit ball of a real Hilbert space. In this work we study the probability of the nonlocal nature of these correlations as a function of {α=m/n}, where the previous vectors are sampled according to the Haar measure in the unit sphere of {R^m}. In particular, we prove the existence of an {α_0 > 0} such that if {α≤ α_0}, {γ} is nonlocal with probability tending to 1 as {n→ ∞}, while for {α > 2}, {γ} is local with probability tending to 1 as {n→ ∞}.

  19. Nonlocal neurology: beyond localization to holonomy.

    PubMed

    Globus, G G; O'Carroll, C P

    2010-11-01

    The concept of local pathology has long served neurology admirably. Relevant models include self-organizing nonlinear brain dynamics, global workspace and dynamic core theories. However such models are inconsistent with certain clinical phenomena found in Charles Bonnet syndrome, disjunctive agnosia and schizophrenia, where there is disunity of content within the unity of consciousness. This is contrasted with the split-brain case where there is disunity of content and disunity of consciousnesses. The development of quantum brain theory with it nonlocal mechanisms under the law of the whole ("holonomy") offers new possibilities for explaining disintegration within unity. Dissipative quantum brain dynamics and its approach to the binding problem, memory and consciousness are presented. A nonlocal neurology armed with a holonomic understanding might see more deeply into what clinical neurology has always aspired to: the patient as a whole.

  20. Delayed-choice Measurement and Temporal Nonlocality

    NASA Astrophysics Data System (ADS)

    Kim, Ilki; Mahler, Günter

    2001-02-01

    We study for a composite quantum system with a quantum Turing architecture the temporal non-locality of quantum mechanics by using the temporal Bell inequality, which will be derived for a discretized network dynamics by identifying the subsystem indices with (discrete) parameter time. However, the direct "observation" of the quantum system will lead to no violation of the temporal Bell inequality and to consistent histories of any subsystem. Its violation can be demonstrated, though, for a delayedchoice measurement

  1. Switching non-local vector median filter

    NASA Astrophysics Data System (ADS)

    Matsuoka, Jyohei; Koga, Takanori; Suetake, Noriaki; Uchino, Eiji

    2016-04-01

    This paper describes a novel image filtering method that removes random-valued impulse noise superimposed on a natural color image. In impulse noise removal, it is essential to employ a switching-type filtering method, as used in the well-known switching median filter, to preserve the detail of an original image with good quality. In color image filtering, it is generally preferable to deal with the red (R), green (G), and blue (B) components of each pixel of a color image as elements of a vectorized signal, as in the well-known vector median filter, rather than as component-wise signals to prevent a color shift after filtering. By taking these fundamentals into consideration, we propose a switching-type vector median filter with non-local processing that mainly consists of a noise detector and a noise removal filter. Concretely, we propose a noise detector that proactively detects noise-corrupted pixels by focusing attention on the isolation tendencies of pixels of interest not in an input image but in difference images between RGB components. Furthermore, as the noise removal filter, we propose an extended version of the non-local median filter, we proposed previously for grayscale image processing, named the non-local vector median filter, which is designed for color image processing. The proposed method realizes a superior balance between the preservation of detail and impulse noise removal by proactive noise detection and non-local switching vector median filtering, respectively. The effectiveness and validity of the proposed method are verified in a series of experiments using natural color images.

  2. EPR paradox, quantum nonlocality and physical reality

    NASA Astrophysics Data System (ADS)

    Kupczynski, M.

    2016-03-01

    Eighty years ago Einstein, Podolsky and Rosen demonstrated that instantaneous reduction of wave function, believed to describe completely a pair of entangled physical systems, led to EPR paradox. The paradox disappears in statistical interpretation of quantum mechanics (QM) according to which a wave function describes only an ensemble of identically prepared physical systems. QM predicts strong correlations between outcomes of measurements performed on different members of EPR pairs in far-away locations. Searching for an intuitive explanation of these correlations John Bell analysed so called local realistic hidden variable models and proved that correlations consistent with these models satisfy Bell inequalities which are violated by some predictions of QM and by experimental data. Several different local models were constructed and inequalities proven. Some eminent physicists concluded that Nature is definitely nonlocal and that it is acting according to a law of nonlocal randomness. According to these law perfectly random, but strongly correlated events, can be produced at the same time in far away locations and a local and causal explanation of their occurrence cannot be given. We strongly disagree with this conclusion and we prove the contrary by analysing in detail some influential finite sample proofs of Bell and CHSH inequalities and so called Quantum Randi Challenges. We also show how one can win so called Bell's game without violating locality of Nature. Nonlocal randomness is inconsistent with local quantum field theory, with standard model in elementary particle physics and with causal laws and adaptive dynamics prevailing in the surrounding us world. The experimental violation of Bell-type inequalities does not prove the nonlocality of Nature but it only confirms a contextual character of quantum observables and gives a strong argument against counterfactual definiteness and against a point of view according to which experimental outcomes are produced

  3. Nonlocal soliton scattering in random potentials

    NASA Astrophysics Data System (ADS)

    Piccardi, Armando; Residori, Stefania; Assanto, Gaetano

    2016-07-01

    We experimentally investigate the transport behaviour of nonlocal spatial optical solitons when launched in and interacting with propagation-invariant random potentials. The solitons are generated in nematic liquid crystals; the randomness is created by suitably engineered illumination of planar voltage-biased cells equipped with a photosensitive wall. We find that the fluctuations follow a super-diffusive trend, with the mean square displacement lowering for decreasing spatial correlation of the noise.

  4. Kummer solitons in strongly nonlocal nonlinear media

    NASA Astrophysics Data System (ADS)

    Zhong, Wei-Ping; Belić, Milivoj

    2009-01-01

    We solve the three-dimensional (3D) time-dependent strongly nonlocal nonlinear Schrödinger equation (NNSE) in spherical coordinates, with the help of Kummer's functions. We obtain analytical solitary solutions, which we term the Kummer solitons. We compare analytical solutions with the numerical solutions of NNSE. We discuss higher-order Kummer spatial solitons, which can exist in various forms, such as the 3D vortex solitons and the multipole solitons.

  5. Nonlocal boundary value problem for telegraph equations

    NASA Astrophysics Data System (ADS)

    Ashyralyev, Allaberen; Modanli, Mahmut

    2015-09-01

    In this work, the nonlocal boundary value problem for a telegraph equation in a Hilbert space is conceived. Stability estimates for the solution of this problem are obtained. The first and second order of accuracy difference schemes for the approximate solution of this problem are constructed. Stability estimates for the solution of these difference schemes are established. In implementations, two mixed problems for telegraph partial differential equations are investigated. The methods are showed by numerical experiments.

  6. Connection between Bell nonlocality and Bayesian game theory.

    PubMed

    Brunner, Nicolas; Linden, Noah

    2013-01-01

    In 1964, Bell discovered that quantum mechanics is a nonlocal theory. Three years later, in a seemingly unconnected development, Harsanyi introduced the concept of Bayesian games. Here we show that, in fact, there is a deep connection between Bell nonlocality and Bayesian games, and that the same concepts appear in both fields. This link offers interesting possibilities for Bayesian games, namely of allowing the players to receive advice in the form of nonlocal correlations, for instance using entangled quantum particles or more general no-signalling boxes. This will lead to novel joint strategies, impossible to achieve classically. We characterize games for which nonlocal resources offer a genuine advantage over classical ones. Moreover, some of these strategies represent equilibrium points, leading to the notion of quantum/no-signalling Nash equilibrium. Finally, we describe new types of question in the study of nonlocality, namely the consideration of nonlocal advantage given a set of Bell expressions. PMID:23820748

  7. Conditions for the confirmation of three-particle nonlocality

    SciTech Connect

    Mitchell, Peter; Roberts, David; Popescu, Sandu

    2004-12-01

    The notion of genuine three-particle nonlocality introduced by Svetlichny [Phys. Rev. D 35, 10, 3066 (1987)] is discussed. Svetlichny's inequality, which can distinguish between genuine three-particle and three-particle nonlocality that is based on underlying two-particle nonlocality, is analyzed by reinterpreting it as a frustrated network of correlations. Its quantum-mechanical maximum violation is derived and a situation is presented that produces the maximum violation. We show that recent beautiful experiments to demonstrate nonlocality for a three-party state by the GHZ paradox, although demonstrating nonlocality, do not allow any violation of the Svetlichny inequality. However, we show that with only minor modifications to the measurements performed, the experiments would be far more powerful and able to demonstrate genuine three-party nonlocality.

  8. Gap solitons under competing local and nonlocal nonlinearities

    SciTech Connect

    Kuo, Kuan-Hsien; Lin Yuanyao; Lee, Ray-Kuang; Malomed, Boris A.

    2011-05-15

    We analyze the existence, bifurcations, and shape transformations of one-dimensional gap solitons (GSs) in the first finite band gap induced by a periodic potential built into materials with local self-focusing and nonlocal self-defocusing nonlinearities. Originally stable on-site GS modes become unstable near the upper edge of the band gap with the introduction of the nonlocal self-defocusing nonlinearity with a small nonlocality radius. Unstable off-site GSs bifurcate into a new branch featuring single-humped, double-humped, and flat-top modes due to the competition between local and nonlocal nonlinearities. The mechanism underlying the complex bifurcation pattern and cutoff effects (termination of some bifurcation branches) is illustrated in terms of the shape transformation under the action of the varying degree of the nonlocality. The results of this work suggest a possibility of optical-signal processing by means of the competing nonlocal and local nonlinearities.

  9. Numerical fluid solutions for nonlocal electron transport in hot plasmas: Equivalent diffusion versus nonlocal source

    SciTech Connect

    Colombant, Denis Manheimer, Wallace

    2010-06-01

    Flux limitation and preheat are important processes in electron transport occurring in laser produced plasmas. The proper calculation of both of these has been a subject receiving much attention over the entire lifetime of the laser fusion project. Where nonlocal transport (instead of simple single flux limit) has been modeled, it has always been with what we denote the equivalent diffusion solution, namely treating the transport as only a diffusion process. We introduce here a new approach called the nonlocal source solution and show it is numerically viable for laser produced plasmas. It turns out that the equivalent diffusion solution generally underestimates preheat. Furthermore, the advance of the temperature front, and especially the preheat, can be held up by artificial 'thermal barriers'. The nonlocal source method of solution, on the other hand more accurately describes preheat and can stably calculate the solution for the temperature even if the heat flux is up the gradient.

  10. Light steering in a strongly nonlocal nonlinear medium

    SciTech Connect

    Ouyang Shigen; Hu Wei; Guo Qi

    2007-11-15

    With a strongly nonlocal model, we present an analytical solution of the coherent interaction of two Gaussian beams with an arbitrary phase difference and arbitrary incident angles. Numerical simulations show that the analytical solution can describe the interaction of two Gaussian beams very well in the strongly nonlocal case. It is theoretically shown that one can steer lights in strongly nonlocal media by tuning the incident conditions of coherently interacting beams like the phase difference between beams and their relative amplitude.

  11. Exact solutions for a coupled nonlocal model of nanobeams

    NASA Astrophysics Data System (ADS)

    de Sciarra, Francesco Marotti; Barretta, Raffaele

    2014-10-01

    Bernoulli-Euler nanobeams under concentrated forces/couples with the nonlocal constitutive behavior proposed by Eringen do not exhibit small-scale effects. A new model obtained by coupling the Eringen and gradient models is formulated in the present note. A variational treatment is developed by imposing suitable thermodynamic restrictions for nonlocal models and the ensuing differential and boundary conditions of elastic equilibrium are provided. The nonlocal elastostatic problem is solved in a closed-form for nanocantilever and clamped nanobeams.

  12. Exact solutions for a coupled nonlocal model of nanobeams

    SciTech Connect

    Marotti de Sciarra, Francesco E-mail: raffaele.barretta@unina.it; Barretta, Raffaele E-mail: raffaele.barretta@unina.it

    2014-10-06

    BERNOULLI-EULER nanobeams under concentrated forces/couples with the nonlocal constitutive behavior proposed by ERINGEN do not exhibit small-scale effects. A new model obtained by coupling the ERINGEN and gradient models is formulated in the present note. A variational treatment is developed by imposing suitable thermodynamic restrictions for nonlocal models and the ensuing differential and boundary conditions of elastic equilibrium are provided. The nonlocal elastostatic problem is solved in a closed-form for nanocantilever and clamped nanobeams.

  13. Accurate relativistic energy-consistent pseudopotentials for the superheavy elements 111 to 118 including quantum electrodynamic effects

    NASA Astrophysics Data System (ADS)

    Hangele, Tim; Dolg, Michael; Hanrath, Michael; Cao, Xiaoyan; Schwerdtfeger, Peter

    2012-06-01

    Energy-consistent two-component semi-local pseudopotentials for the superheavy elements with atomic numbers 111-118 have been adjusted to fully relativistic multi-configuration Dirac-Hartree-Fock calculations based on the Dirac-Coulomb Hamiltonian, including perturbative corrections for the frequency-dependent Breit interaction in the Coulomb gauge and lowest-order quantum electrodynamic effects. The pseudopotential core includes 92 electrons corresponding to the configuration [Xe]4f 145d105f 14. The parameters for the elements 111-118 were fitted by two-component multi-configuration Hartree-Fock calculations in the intermediate coupling scheme to the total energies of 267 up to 797 J levels arising from 31 up to 62 nonrelativistic configurations, including also anionic and highly ionized states, with mean absolute errors clearly below 0.02 eV for averages corresponding to nonrelativistic configurations. Primitive basis sets for one- and two-component pseudopotential calculations have been optimized for the ground and excited states and exhibit finite basis set errors with respect to the finite-difference Hartree-Fock limit below 0.01 and 0.02 eV, respectively. General contraction schemes have been applied to obtain valence basis sets of polarized valence double- to quadruple-zeta quality. Results of atomic test calculations in the intermediate coupling scheme at the Fock-space coupled-cluster level are in good agreement with those of corresponding fully relativistic all-electron calculations based on the Dirac-Coulomb-Breit Hamiltonian. The results demonstrate besides the well-known need of a relativistic treatment at the Dirac-Coulomb level also the necessity to include higher-order corrections for the superheavy elements.

  14. Accurate relativistic energy-consistent pseudopotentials for the superheavy elements 111 to 118 including quantum electrodynamic effects.

    PubMed

    Hangele, Tim; Dolg, Michael; Hanrath, Michael; Cao, Xiaoyan; Schwerdtfeger, Peter

    2012-06-01

    Energy-consistent two-component semi-local pseudopotentials for the superheavy elements with atomic numbers 111-118 have been adjusted to fully relativistic multi-configuration Dirac-Hartree-Fock calculations based on the Dirac-Coulomb Hamiltonian, including perturbative corrections for the frequency-dependent Breit interaction in the Coulomb gauge and lowest-order quantum electrodynamic effects. The pseudopotential core includes 92 electrons corresponding to the configuration [Xe]4f(14)5d(10)5f(14). The parameters for the elements 111-118 were fitted by two-component multi-configuration Hartree-Fock calculations in the intermediate coupling scheme to the total energies of 267 up to 797 J levels arising from 31 up to 62 nonrelativistic configurations, including also anionic and highly ionized states, with mean absolute errors clearly below 0.02 eV for averages corresponding to nonrelativistic configurations. Primitive basis sets for one- and two-component pseudopotential calculations have been optimized for the ground and excited states and exhibit finite basis set errors with respect to the finite-difference Hartree-Fock limit below 0.01 and 0.02 eV, respectively. General contraction schemes have been applied to obtain valence basis sets of polarized valence double- to quadruple-zeta quality. Results of atomic test calculations in the intermediate coupling scheme at the Fock-space coupled-cluster level are in good agreement with those of corresponding fully relativistic all-electron calculations based on the Dirac-Coulomb-Breit Hamiltonian. The results demonstrate besides the well-known need of a relativistic treatment at the Dirac-Coulomb level also the necessity to include higher-order corrections for the superheavy elements. PMID:22697528

  15. Heuristic theory of nonlocally broken gyro-Bohm scaling

    SciTech Connect

    Waltz, R.E.; Candy, J.

    2005-07-15

    Global gyrokinetic simulations of ion temperature gradient turbulent transport with piecewise-flat profiles are given to illustrate the breaking of gyro-Bohm scaling by a nonlocal mechanism. The nonlocal drainage of the turbulence from unstable regions spreading into stable (or less unstable) regions breaks the gyro-Bohm scaling toward Bohm in unstable regions and toward super-gyro-Bohm in stable (or less unstable) regions. A heuristic model for this nonlocal process is formulated in terms of a nonlocal growth rate resulting from a locally weighted radial average of the local linear ballooning mode growth rate. A nonlocality length L measured in ion gyroradii provides the exponential scale for the local weighting. The nonlocal growth rate can be incorporated into a local gyro-Bohm-scaled transport model in place of the local growth rate. The resulting nonlocal transport model will provide some transport in stable regions. A heuristic theory of this nonlocal transport mechanism based on the partial formation of global modes in toroidal geometry is detailed. The theory argues that the nonlocality length L increases with relative gyroradius and decreases with the linear growth rate.

  16. Survey on nonlocal games and operator space theory

    NASA Astrophysics Data System (ADS)

    Palazuelos, Carlos; Vidick, Thomas

    2016-01-01

    This review article is concerned with a recently uncovered connection between operator spaces, a noncommutative extension of Banach spaces, and quantum nonlocality, a striking phenomenon which underlies many of the applications of quantum mechanics to information theory, cryptography, and algorithms. Using the framework of nonlocal games, we relate measures of the nonlocality of quantum mechanics to certain norms in the Banach and operator space categories. We survey recent results that exploit this connection to derive large violations of Bell inequalities, study the complexity of the classical and quantum values of games and their relation to Grothendieck inequalities, and quantify the nonlocality of different classes of entangled states.

  17. ACCELERATED MRI USING ITERATIVE NON-LOCAL SHRINKAGE

    PubMed Central

    Mohsin, Yasir Q.; Ongie, Gregory; Jacob, Mathews

    2015-01-01

    We introduce a fast iterative non-local shrinkage algorithm to recover MRI data from undersampled Fourier measurements. This approach is enabled by the reformulation of current non-local schemes as an alternating algorithm to minimize a global criterion. The proposed algorithm alternates between a non-local shrinkage step and a quadratic subproblem. The resulting algorithm is observed to be considerably faster than current alternating non-local algorithms. We use efficient continuation strategies to minimize local minima issues. The comparisons of the proposed scheme with state-of-the-art regularization schemes show a considerable reduction in alias artifacts and preservation of edges. PMID:25570265

  18. The uncertainty principle determines the nonlocality of quantum mechanics.

    PubMed

    Oppenheim, Jonathan; Wehner, Stephanie

    2010-11-19

    Two central concepts of quantum mechanics are Heisenberg's uncertainty principle and a subtle form of nonlocality that Einstein famously called "spooky action at a distance." These two fundamental features have thus far been distinct concepts. We show that they are inextricably and quantitatively linked: Quantum mechanics cannot be more nonlocal with measurements that respect the uncertainty principle. In fact, the link between uncertainty and nonlocality holds for all physical theories. More specifically, the degree of nonlocality of any theory is determined by two factors: the strength of the uncertainty principle and the strength of a property called "steering," which determines which states can be prepared at one location given a measurement at another.

  19. Skyrme functional from a three-body pseudopotential of second order in gradients: Formalism for central terms

    NASA Astrophysics Data System (ADS)

    Sadoudi, J.; Duguet, T.; Meyer, J.; Bender, M.

    2013-12-01

    Background: In one way or another, all modern parametrizations of the nuclear energy density functional (EDF) do not respect the exchange symmetry associated with Pauli's principle. It has been recently shown that this practice jeopardizes multireference (MR) EDF calculations by contaminating the energy with spurious self-interactions that, for example, lead to finite steps or even divergences when plotting it as a function of collective coordinates [J. Dobaczewski , Phys. Rev. CPRVCAN0556-281310.1103/PhysRevC.76.054315 76, 054315 (2007); D. Lacroix , Phys. Rev. CPRVCAN0556-281310.1103/PhysRevC.79.044318 79, 044318 (2009)]. As of today, the only viable option to bypass these pathologies is to rely on EDF kernels that enforce Pauli's principle from the outset by strictly and exactly deriving from a genuine, i.e., density-independent, Hamilton operator.Purpose: The objective is to build cutting-edge parametrizations of the EDF kernel deriving from a pseudopotential that can be safely employed in symmetry restoration and configuration mixing calculations.Methods: We wish to develop the most general Skyrme-like EDF parametrization containing linear, bilinear, and trilinear terms in the density matrices with up to two gradients, under the key constraint that it derives strictly from an effective Hamilton operator. While linear and bilinear terms are obtained from a standard one-body kinetic energy operator and a (density-independent) two-body Skyrme pseudopotential, the most general three-body Skyrme-like pseudopotential containing up to two gradient operators is constructed to generate the trilinear part. The present study is limited to central terms. Spin orbit and tensor will be addressed in a forthcoming paper.Results: The most general central Skyrme-type zero-range three-body interaction is built up to second order in derivatives. The complete trilinear EDF, including time-odd and T=1 pairing parts, is derived along with the corresponding normal and anomalous

  20. Nonlocalization of Nonlocal Symmetry and Symmetry Reductions of the Burgers Equation

    NASA Astrophysics Data System (ADS)

    Jin, Yan; Jia, Man; Lou, Sen-Yue

    2012-12-01

    Symmetry reduction method is one of the best ways to find exact solutions. In this paper, we study the possibility of symmetry reductions of the well known Burgers equation including the nonlocal symmetry. The related new group invariant solutions are obtained. Especially, the interactions among solitons, Airy waves, and Kummer waves are explicitly given.