bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantum corrections to the supersymmetry algebra
Authors: McKeon D. G. C.
Published: April 2011

The Bjorken–Johnson–Low technique is used to compute the equal time anticommutator of the spinor currents associated with the supersymmetry of a two-dimensional Wess–Zumino model containing a Majorana spinor, a scalar, and an auxiliary field. Operator regularization is used to compute radiative effects as this does not explicitly break the supersymmetry present in the classical Lagrangian. We find that the spinor current is not conserved, and that the algebra of the generators of the supersymmetry transformation is altered. This is analogous to what has been found in theories with a classical axial gauge symmetry.
Time delay in quantum coherence and tunneling
Authors: Razavy M. , Pimpale Ashok
Published: April 2011

The problem of time delay in quantum mechanics and its relation to the classical concept of traversal time is studied. For a monochromatic wave, in one dimension, it is shown that the time delay is proportional to a linear combination of the derivatives of the phases of the transmission and reflection coefficients with respect to the frequency. In particular it is shown that the definition of time delay for quantum coherence given in terms of the periods of oscillations of a wave packet between the two wells, in the proper limit, agrees with the corresponding definition in tunneling.
On exact-shearing perfect-fluid solutions of the nonstatic spherically symmetric Einstein field equations
Authors: Biech T. , Das A
Published: April 2011

In this paper we have sought solutions of the nonstatic spherically symmetric field equations that exhibit nonzero shear. The Lorentzian-warped product construction is used to present the spherically symmetric metric tensor in double-null coordinates. The field equations, kinematical quantities, and Riemann invariants are computed for a perfect-fluid stress-energy tensor. For a special observer, one of the field equations reduces to a form that admits wavelike solutions. Assuming a functional relationship between the metric coefficients, the remaining field equation becomes a second-order nonlinear differential equation that may be reduced as well.
Zero-temperature properties of quantum spin systems in two dimensions
Authors: Betts D. D. , Miyashita S.
Published: April 2011

We consider the zero-temperature properties of four different spin 1/2 models on two-dimensional lattices: the XY ferromagnet, the XY antiferromagnet, the Heisenberg antiferromagnet, and the Dzyaloshinsky–Moriya models. Most of this article is a review of previously published work, but a few previously unpublished results are included. The relation between three of the models on bipartite lattices is described. The properties of the XY ferromagnet in two dimensions, especially those derived from extrapolation of finite lattice results, are reviewed. A numerical factor by which spin-wave and finite-lattice estimates of the long-range order parameter differ is discussed. For frustrated models on the triangular lattice the possibility of a chirality phase transition instead of, or in addition to, a magnetic phase transition is considered.
Electromagnetic scattering by an arbitrary configuration of dielectric spheres
Authors: Hamid A-K. , Ciric I. R. , Hamid M.
Published: April 2011

An analytic solution is obtained for the problem of plane electromagnetic-wave scattering by an arbitrary configuration of N dielectric spheres. The multipole expansion method is employed, and the boundary condition is imposed using the translational addition theorem for vector spherical wave functions. A system of simultaneous linear equations is given in matrix form for the scattering coefficients. An approximate solution, which has been developed and employed by the authors for the scattering by N conducting spheres, is extended to the dielectric spheres case. Plots for the normalized backscattering, bistatic, and forward-scattering cross sections are presented over wide ranges of permittivity, size, and electrical separations between the neighbouring spheres. The results show a reduction in the normalized backscattering and bistatic cross sections for certain choices of permittivity relative to conducting arrays of spheres of the same dimensions and separations.
Convection in a viscoelastic fluid-saturated sparsely packed porous layer
Authors: Rudraiah N. , Radhadevi P. V. , Kaloni P. N.
Published: April 2011

The linear stability of a viscoelastic fluid-saturated sparsely packed porous layer heated from below is studied analytically using the Darcy–Brinkman–Jeffreys model with different boundary combinations. The Galerkin technique is employed to determine the criterion for the onset of oscillatory convection. The effects of the viscoelastic parameters, the Prandtl number, and the porous parameter on the critical Rayleigh number, the wave number, and the frequency are analyzed. The results are compared with those obtained for both a Darcy–Jeffrey fluid and a Maxwell fluid. It is shown that under certain conditions for the viscoelastic parameters, the flow is overstable. The possibility of the occurrence of bifurcation is also discussed.
Mass, radius, and moment of inertia for neutron stars
Authors: Øvergård Tommy , Østgaard Erlend
Published: April 2011

Using results from energy calculations of "neutron matter," we construct various equations of state. From these equations of state, together with the Tolman–Oppenheimer–Volkoff equations derived from Einstein's general theory of relativity, we calculate quantities such as pressure, mass density, mass energy density, total mass, radius, and moment of inertia for configurations described in the models. Comparison is made with calculations based on other nuclear potentials and nuclear energy calculations, and our results are in reasonable agreement with results from observational data.
Three-body calculation of deuteron-induced-stripping reactions
Authors: Brinati J. R. , Martins M. H. P.
Published: April 2011

Differential cross sections for the reactions (d,p) and (d,n) are calculated, considering a three-body system with Coulomb interaction and total energies of the system under the break-up threshold. The method used to describe this system is the one proposed by Alt et al. Phys. Rev. C: Nucl. Phys. 17, 1981 (1978). The numerical aspects envolved in the solution of the three-body equations are commented upon. The effect of the Coulomb interaction is exhibited and its importance stressed.
A study of high-purity CdxSe1−x vacuum-deposited thin films
Authors: Dufresne E. , Brodie D. E.
Published: April 2011

Pure CdSe films were vacuum deposited onto liquid-nitrogen-cooled substrates using a doubly baffled source in an attempt to prepare and study amorphous CdSe. The deposition of stable stoichiometric amorphous pure films was not verified since the films were always polycrystalline when analyzed at room temperature. CdSe appears to be different from some other II– VI compounds that can be prepared as pure stoichiometric amorphous materials and can be studied at a temperature up to 400 K. Pure nonstoichiometric films were also prepared using a second source to supply the excess component. Amorphous Se-rich films could only be produced for samples with at least 59 at.% Se. For Cd-rich films, the excess Cd agglomerates and the CdSe crystallite sizes are smaller than those observed in stoichiometric films. The electrical and optical properties scale as a function of the Cd content and the films become metallike as the Cd content increases through 60 at.%. The electrical transport properties are very different for polycrystalline films, depending on whether the CdSe is deposited on a hot substrate, or on a cold substrate and annealed to the same high temperature. We show that impure amorphous films of CdSe can be deposited if the system's background pressure is high.
Nuclear-mass dependent spin-orbit interaction
Authors: Sordo T. L. , Sordo J. A. , Fraga S.
Published: April 2011

The nuclear-mass dependent spin-orbit interaction is discussed. The corresponding interaction operator is given in tensor form and the expression for its matrix elements in a basis of SL functions is presented. Monoconfigurational calculations have been performed for the ground states of carbon and oxygen. The results for the J-level splittings show that the contribution from this interaction is comparable with, or even greater than, the contribution from the hyperfine-structure interactions.
Some properties of amorphous hydrogenated silicon nitride prepared by ion-beam-assisted deposition
Authors: Wilson P. , Craigen D. C. , Brodie D. E.
Published: April 2011

Thin films of a-SiNx:H were deposited using the ion-beam-assisted deposition technique. Silicon was evaporated from a resistively heated carbon crucible while the substrate was bombarded with low-energy ions (100 eV). The feed gas used for the ion source was primarily ammonia (NH3), but a 90% nitrogen, 10% hydrogen mixture was also tried. The nitrogen–hydrogen mixture resulted in nonhydrogenated films. Both the absence of absorption in the IR spectrum owing to oxygen, and the increase in slope of the Tauc plots are evidence of an improvement in film morphology owing to the ion bombardment. The wide band-gap films photoconduct when exposed to UV light. The photoconducting property is lost when the films are exposed to air, and is restored when the samples are thermally annealed in a vacuum.
Beam-foil lifetime measurements for some 5d10nl and 5d96s6p levels of Pb IV
Authors: Pinnington E. H. , Ansbacher W. , Tauheed A. , Kernahan J. A.
Published: April 2011

The beam-foil technique was used to measure the lifetimes of the 5d105f, 5g, 6d, 6h, 7p, 7d, 8s and 5d96s6p [2]0, [3]0, [6]0, [14]0, [17]0 levels of Pb IV. Correlated decay-curve analyses were used to correct for the effects of cascading in the case of the 5d105f, 5g, 6d, and 7p levels. The numerical Coulomb approximation was used to calculate comparison values for the 5d10nl levels. The need for a more rigorous calculation for specific levels is discussed.
1s hole excited states of Be: partial autoionization rates compared with recent experimental data
Authors: Petrini D. , Tully J. A.
Published: April 2011

Auger decay following inner-shell photoexcitation of atomic beryllium is studied using the University College London close-coupling codes. We reproduce some of the features observed experimentally by Krause and co-workers. The vastly predominant decay mode of Be 1s2s2np1P° is to Be+ 1s2np rather than the ground state of Be+ and the theoretical np/2s ratio agrees with the experimental value. The peak observed in the partial photoionization cross section for formation of 1s(2s2p3P) 2P° is due to photoexcitation of 1s2s(3s3p3P) 1P° followed by autoionization. Our theoretical result reproduces this feature. Strong configuration interaction effects limit the accuracy we can achieve for the radiationless decay width.
On the theory of the Stark shifts of the rotational–vibrational levels of the hydrogen molecule and its isotopes produced by a point charge. II: HD, HT, and DT
Authors: Miller J. J. , Poll J. D. , Hunt J. L.
Published: April 2011

In continuation of paper I of this series on the homonuclear molecules H2, D2, and T2, the Hamiltonian describing the rotation and vibration of a heteronuclear molecule in the field of a point charge is given. Numercial results for the Stark shift of the molecular levels due to a point charge of either sign are listed for HD, HT, and DT as a function of the separation of this charge from the molecule. An application of the calculations to the charge-induced spectrum of HD is presented.
On the cutoff conditions and power distribution in fibres of arbitrary cross section
Authors: Bhattacharjee S. , Menon V. J. , Dey K. K.
Published: April 2011

A recently developed general theory of propagation constants in weakly guiding, noncircular fibres is extended to derive simple, analytical expressions for the modal cutoff frequencies and relative power content of the core. The results are illustrated numerically for elliptic fibres of small eccentricity, and also interpreted physically.
Discrete lattice model for the large polaron
Authors: Paranjape V. V. , Panat P. V.
Published: April 2011

The energy states of a polaron in the weak-coupling limit were first obtained by Fröhlich and co-workers, assuming that the polarization of the lattice due to the electron is continuous. If the polaron radius is comparable to the lattice constant then the assumption is inappropriate. A model based on the discrete nature of the lattice is more suitable. Such a model, based on the semiclassical zero-point energy, is proposed. We have calculated the ground-state energy of the polaron and the energy of the polaron near the bottom of the conduction band. The first discussion of the effect of lattice discreteness on the polaron energy was presented by Lepine and Frongillo who used for their calculations, a method based on the "kq" representation. Our method differs from the method of these earlier authors but the results of the two approaches are similar. Some differences exist nevertheless. The main aim of this paper is, therefore, to provide an alternate method for calculating the effect of discreteness on the polaron energy. The differences arising between the results of the two methods are discussed.
Prediction of the onset energy of the fine-structure transition in neon charge transfer
Authors: Howard Stephen L.
Published: April 2011

Data from previous crossed-beam experiments have demonstrated a low-energy onset of the endoergic fine-structure transition in the charge-transfer reaction of rare gases. Correlation of the spin-orbit energies within this group of the periodic table with the onset collision energy from these experiments is used to predict the onset energy for Ne. The correlation also shows that a three-dimensional model should be used to theoretically describe the intermediate R2+ instead of a one-dimensional model.
Thermal neutron capture γ-ray spectrum of molybdenum and ruthenium
Authors: Islam M. A. , Kennett T. J. , Prestwich W. V.
Published: April 2011

The thermal neutron capture γ rays from natural molybdenum and ruthenium have been studied using a pair spectrometer and the tangential facility at the McMaster University Nuclear Reactor. Precise transition, level, and neutron separation energies of different isotopes are inferred. The separation energies are: Sn(93Mo) = 8069.76 ± 0.09, Sn(95Mo) = 7369.10 ± 0.10, Sn(96Mo) = 9154.31 ± 0.05, Sn(97Mo) = 6821.15 ± 0.25, Sn(98Mo) = 8642.55 ± 0.07, Sn(99Mo) = 5925.42 ± 0.15, Sn(100Ru) = 9673.48 ± 0.05, and Sn(102Ru) = 9219.64 ± 0.05 keV. The M1 strength functions of 100Ru,102Ru, 96Mo, and 98Mo are (34 ± 15) × 10−9, (82 ± 41) × 10−9, (22 ± 7) × 10−9, and (25 ± 8) × 10−9 MeV−3, respectively. All values but that for 102Ru agree with the global average of (20 ± 6) × 10−9 MeV−3. The average [Formula: see text] of 96Mo observed is 247 ± 175 e2 fm4 MeV−1.
Exact solutions to Klein–Gordon and Weyl equations in a perfect-fluid Einstein–Maxwell space-time with local rotational symmetry
Authors: Percoco Umberto , Villalba Victor M.
Published: April 2011

In this article we exhibit exact solutions of the Klein–Gordon and Weyl equations in a space-time homogeneous metric with local rotational symmetry, and the solutions of the Einstein–Maxwell equations with a perfect-fluid source and a sinusoidal electromagnetic configuration.
Hadronization and confinement in quantum chromodynamics
Authors: Pervushin V. N. , Han Nguyen Suan
Published: April 2011

We discuss the consistency of the standard ideas of confinement with the recent phenomenological procedure of measurement of colour quantum numbers. We show that the scheme of quantization of gauge fields, most adequate for the covariant description of hadrons, also contains a confinement mechanism as a destructive interference of phase factors of topological degeneration.
Observation of continuous KrCl excimer fluorescence in microwave discharges employing binary mixtures of Kr and Cl2
Authors: Hassal Scott B. , Ballik Edward A.
Published: April 2011

A novel apparatus was designed to couple 2.45-GHz microwave radiation into a gas discharge. Using this apparatus, continuous-wave 222-nm B → X fluorescence of the KrF excimer system was observed in a binary mixture of chlorine and krypton. The effects of gas composition and total pressure on the fluorescence intensity at a wavelength of 222 nm was investigated. Spectra over the wavelength region of 200–320 nm were recorded for various gas compositions near the optimum total pressures for excimer fluorescence. The 222-nm B → X KrCl excimer transition was apparent in all cases and had a full-width half-maximum (FWHM) of 3 nm. In addition, the 258-nm Cl2 excimer transition was also evident with a FWHM of 5 nm. Both the center frequencies and widths of these transitions were constant for the conditions tested.
Comparison of WKB (Wentzel–Kramers–Brillouin) and SWKB solutions of Fokker–Planck equations with exact results; application to electron thermalization
Authors: Shizgal Bernie , Demeio Lucio
Published: April 2011

A comparison of WKB (Wentzel–Kramers–Brillouin) and SWKB eigenfunctions of the Schrödinger equation for potentials in the class encountered in supersymmetric quantum mechanics is presented. The potentials that are studied are those that result from the transformation of a Fokker–Planck eigenvalue problem to a Schrödinger equation. Linear Fokker–Planck equations of the type considered in this paper give the probability distribution function for a large number of physical situations. The time-dependent solutions can be expressed as a sum of exponential terms with each term characterized by an eigenvalue of the Fokker–Planck operator. The specific Fokker–Planck operator considered is the one that describes the thermalization of electrons in the inert gases. The WKB and SWKB semiclassical approximations are compared with exact numerical results. Although the eigenvalues can be very close to the exact values, we find significant departures for the eigenfunctions.
Theoretical study of the electronic structure of covalent solids
Authors: Khan D. C. , Khowash P. K.
Published: April 2011

The aim of this work is to study theoretically the electronic structure of a number of ionic and covalent solids. The charges within each atomic region are calculated and a charge-transfer diagram is introduced to define a measure of the chemical bonding (ionic and (or) covalent) in these systems. The crystal-field splitting, 10 Dq, is determined for crystals with a 3d cation from the one-electron energy spectra and compared with available experiments. The transition between two of the valence levels is calculated wherever the corresponding X-ray photoelectron spectrometry or optical spectroscopic experimental data exist in the literature. Finally, the Mössbauer isomer shifts are calculated for iron containing samples.
On the surface photoeffect in a heavily doped semiconductor
Authors: De S. S. , Ghosh A. K. , Pattanayak T. K.
Published: April 2011

The surface photoeffect in a heavily doped semiconductor was investigated using the influences of band-gap narrowing and carrier degeneracy. Variation of the surface photovoltage with the normalized surface potential is presented graphically. A comparison with earlier work done under identical conditions is made. The temperature-dependent behaviour is also studied.
Some properties of flash-evaporated Ga1−xAsx films
Authors: Harwood M. R. , Brodie D. E.
Published: April 2011

a-Ga1−xAsx films containing small GaAs crystallites were prepared by flash evaporation onto low-temperature glass substrates. The As content in the films was varied from 41 to 69 at.%. Thermoelectric power measurements indicate that Ga-rich films are n-type and As-rich films are p-type, but the Seebeck coefficients for samples near the stoichiometric ratio were too small to measure. The optical gaps vary with As content in a way that is consistent with the suggestion that the material appears to be an alloy of a-GaAs and the excess component. High-temperature activation energies place the Fermi level near midgap in all samples and this is in line with the suggestion that this class of materials tend to self compensate as the film grows.
Stability of internally generated thermal convection in a tall vertical annulus
Authors: Kolyshkin A. , Vaillancourt Rémi
Published: April 2011

The stabilityof a convective fluid motion generated by internal heat sources in a tall vertical annulus is investigated by means of a mathematical model in the cases of both axisymmetric and asymmetric disturbances. The critical Grasshof numbers are computed for several values of the Prandtl number and different sizes of the gap between the cylinders. It is found that, for low Prandtl numbers and large gaps, asymmetric disturbances lead to instability while, in the case of small gaps, instability is associated with axisymmetric disturbances. In both cases, the critical Grasshof number increases as the gap decreases. For high values of the Prandtl number, instability occurs in the form of thermal running waves. The critical Grasshof numbers decrease as the Prandtl number grows. The neutral stability curve has one or two closed loops for sufficiently high Prandtl numbers. It is found that for high Prandtl numbers instability is associated with axisymmetric perturbations at least in the interval 0.05 < R < 1, where R is the ratio of the inner to the outer radii.
Magnetic field penetration into YBa2Cu3O7 thin film deposited on a cleaved MgO substrate
Authors: Batalla E. , Zwartz E. G. , Wright L. S. , Grant P. D. , Denhoff M. W.
Published: April 2011

A thin film of YBa2Cu3O7 was deposited by laser ablation onto the (001) surface of a cleaved MgO substrate. The magnetic field penetration into the thin film was photographed using a magneto-optic apparatus. The field penetrates into the sample along specific directions that we identify with the cleavage steps that are more than 0.25 μm high.
Interfacial wave theory of two-dimensional dendritic growth with anisotropy of surface tension
Authors: Xu Jian-Jun
Published: April 2011

In this paper, we consider two-dimensional dendritic growth from pure melt with inclusion of the anisotropy of surface tension. The interfacial wave theory previously established for axisymmetric dendritic growth is extended to this case. The results show that the effect of the anisotropy of surface tension on the selection condition of the tip velocity is not significant.
Fourth-order elastic constants and second pressure derivatives of white tin
Authors: Rao R. Ramji , Padmaja A.
Published: April 2011

The expressions for the 25 fourth-order elastic constants of a body-centered tetragonal crystal are derived with interactions extending to fifth neighbours. The expressions for its effective second-order elastic constants are obtained in terms of its natural second-, third-, and fourth-order elastic constants using the finite strain elasticity theory. The fourth-order elastic constants and the second pressure derivatives of white tin are evaluated using these formulae. All the second pressure derivatives of white tin except that of C11 are positive. The second pressure derivatives C12, C13, and C33 are large suggesting that phase transformation will occur in white tin when subjected to hydrostatic pressure.
Distribution of quantum states in enclosures of finite size: I
Authors: Souto J. Hugo , Chaba A. N.
Published: April 2011

We show that the expression for the density of states of a particle in a three-dimensional rectangular box of finite size can be obtained by using directly the Poisson's summation formula instead of using the Walfisz formula or the generalized Euler formula both of which can be derived from the former. We also derive the expression for the density of states in the case of an enclosure in the form of an infinite rectangular slab and apply it to the problem of the Bose–Einstein condensation of a Bose gas of noninteracting particles confined to a thin-film geometry.
Classical motion of a point particle with extrinsic curvature
Authors: McKeon D. G. C.
Published: April 2011

We consider the classical motion of a point particle whose Lagrangian involves not only the usual arc length, but also the extrinsic curvature associated with its trajectory. This Lagrangian is independent of the parameterization used to characterize the trajectory; by choosing this parameter to be the time coordinate associated with the position of the particle in space-time, we obtain a Lagrangian dependent on the position, velocity, and acceleration of the particle in a co-moving frame. Some special solutions to the Hamiltonian equations of motion are presented for the case of the free particle and for a particle moving in a Coulomb field.
Berry's phase for U(1/1) coherent states
Authors: Schmitt H. A. , Mufti A.
Published: April 2011

Berry's geometrical phase is calculated for the coherent states of the compact unitary supergroup U(1/1). With properly chosen parameters, these coherent states are shown to be eigenstates of the nonresonant two-level Jaynes–Cummings Hamiltonian.
Rydberg series in the arc spectrum of antimony
Authors: Jones William E. , Martell Jaime M.
Published: April 2011

The absorption spectrum of antimony vapour produced by the flash discharge of SbF5 vapour was photographed in the region 1320–1700 Å (1 Å = 10−10 m) by means of a 10 m vacuum spectrograph. Of a total of 302 absorption lines observed, 203 were classified into 11 Rydberg series, two of which are autoionized. Four of the series have not been previously reported, and a total of 142 new lines are added to the previous analyses. The ionization limits for the 3P multiplet of Sb II were also refined.
Wave equation for dissipative motion
Authors: Razavy M.
Published: April 2011

From a quantized many-body system a wave equation for the motion of a particle linearly coupled to a heat bath is derived. The effective Hamiltonian describing the motion of the single particle is explicitly time dependent, and for a quadratic potential, has a simple dependence on the initial position and momentum of the particle. For the case of dissipative harmonic motion, a time-dependent wave equation is derived and the ground-state wave function is determined. It is also shown that if the equations of motion for the many-body system is Galilean invariant, the reduced form of equation of motion for the single particle is not. However a generalized form of transformation for the position and momentum operators, to a coordinate system moving with constant velocity, is obtained, which reduces to the Galilean transformation when the coupling to the dissipative system is turned off.
Measurements of nitrogen-shifting coefficients of water-vapor lines between 5000 and 10 700 cm−1
Authors: Chevillard J.-P. , Mandin J.-Y. , Flaud J.-M. , Camy-Peyret C.
Published: April 2011

More than 180 nitrogen-shifting coefficients have been measured at 300 K, for vibro-rotational lines of the water molecule absorbing between 5000 and 10 700 cm−1. The average uncertainty is 0.4 × 10−3 cm−1 atm−1 (1 atm = 1013 hPa); most of the measured N2-shifting coefficients are negative, they vary between +5 and −27 × 10−3 cm−1 atm−1. A review of the existing measurements and calculations concerning the pressure-shifts of H2O lines is presented, and the measurement methodology is discussed.
Charge screening in Born–Infeld theory by magnetic charge of another U(1) gauge group
Authors: Wolf C.
Published: April 2011

We calculate the screening of an electric charge brought about by the coupling of electromagnetism to a second gauge group carrying magnetic charge. The resultant classical calculation demonstrates that the electric charge is antiscreened by magnetic charge. The total mass of the configuration is also evaluated including that due to the coupling of electromagnetism to the magnetic charge of a second U(1) gauge group.
A comparative study of , , and nuclei
Authors: Mehrotra I.
Published: April 2011

Binding energies of Λ, Λc, and Λb baryons in [Formula: see text], [Formula: see text], and [Formula: see text] are estimated taking into account the corrections due to the centre-of-mass motion and also the Coulomb correction in [Formula: see text]. Both these corrections turn out to be quite important. Just bound states for [Formula: see text], and [Formula: see text] are obtained for Λc–N and Λb–N interactions, which are weaker than the Λ–N interaction by nearly 55% and 30%, respectively.
Spectrum of the Coulomb-plus-Yukawa potential by the method of potential envelopes
Authors: Duarte J. Paul , Hall Richard L.
Published: April 2011

The method of potential envelopes is used to analyse the bound-state spectrum of the Schrödinger Hamiltonian H = −Δ + V(r), where V(r) = −β/r + γe−λr/r, γ < β. It is established that upper or lower bounds to the eigenenergies Enl(β,γ,λ) are generated by the simple formula, [Formula: see text] where [Formula: see text] if γ < 0 and [Formula: see text] if γ > 0. The results are compared with eigenvalues computed numerically by a finite-element method and also with the results of a variational calculation.
A study of the multiparticle production process in 340 GeV/c π− interactions with emulsion nuclei using the method of rapidity-gap distribution of showers
Authors: Tufail A. , Taiyab Taiyab , Ahmad S. , Khan A. R. , Zafar M. , Shafi M.
Published: April 2011

The multiparticle production process was investigated using the method of rapidity-gap distribution of showers. To eliminate the phase-space effects from these distributions, pseudoevents were generated. The short-range rapidity-gap correlation observed is greater than expected for a phase-space effect thus giving evidence for the production of clusters in the process.
Effective Hamiltonian and generalized Ginzburg–Landau theory
Authors: Peng Huei , Wang K.
Published: April 2011

We propose an effective Hamiltonian for the Ginzburg–Landau theory of a superconductor at rest. This yields the ordinary, and a time-dependent generalized Ginzburg–Landau theory. Then we generalize the Hamiltonian and derive a generalized Ginzburg–Landau theory for non-uniformly moving superconductors. We show that the fluxoid in a singly connected rotating superconductor is quantized.
Slow and fast electron concentrations: Their relation to conductivity and superconductivity
Authors: MacDougall Preston J.
Published: April 2011

We consider the physical significance of the topology of the Laplacian of the electron momentum density, [Formula: see text]. Via a single simple postulate, the electrical properties of metals, superconductors, and insulators are herein linked to well–defined and observable topological features in this distribution. From this postulate it follows that a necessary condition for superconductivity is a closed path of cusp singularities in the material's time-averaged Π(p) distribution. The topology of the path is constrained by the geometry of the sample and its environment. Yet, by virtue of the postulate, the unique collision properties of this path (in momentum space) suggest that it charts a common course for electrons throughout the material, along which there is absolute minimum resistance to electron flow. As a further consequence of the postulate, it is also predicted that the preferred planes or axes of electron transport in anisotropic conductors will correspond to uniquely and unambiguously defined topological features of the Laplacian of the electron momentum distribution.
The cylindrical couette flow of a rarefied gas consisting of charged particles inside walls with arbitrary reflection coefficients
Authors: Mahmoud M. A. , Shalaby G. A.
Published: April 2011

A kinetic-theory treatment of the cylindrical Couette flow is considered. A generalization of the case of a surface with an arbitrary reflection coefficient that depends on the nature of the surface. In this paper we consider that the reflection coefficients of the inner and outer walls are different. A model kinetic equation of the BGK (Bhatnger–Gross–Krook) type is solved using the method of moments with a two-sided distribution function. The dependence of the velocity and shear stress on the reflection coefficient is obtained.
Low-light-level diffraction experiments: No evidence for anomalous effects
Authors: Jeffers S. , Wadlinger R. , Hunter G.
Published: April 2011

Previously reported diffraction experiments indicated that at low light intensities (at optical powers corresponding to "statistically independent photons") the side lobes of the diffraction patterns disappear and, furthermore, the response of photoelectric detectors to changes in incident optical flux becomes nonlinear. If true, these anomalous effects would have profound consequences for quantum theory and the nature of the photon. This paper reports a similar series of low-intensity diffraction experiments (using two different optoelectronic detectors) the results of which do not substantiate the previously reported anomalous effects.
Light-fragment yield ratios from heavy-ion-induced fragmentation in atmospheric collisions of cosmic-ray primary nuclei
Authors: Pantazopoulou M. J. , Barghouty A. F. , Witt R. A.
Published: April 2011

A statistical nuclear-fragmentation model is used to calculate the total inclusive cross sections and yield ratios of light fragments (p, d, 3H, and 3He) from 800 MeV/nucleon mass-symmetric and mass-asymmetric collision systems. Comparison with available data reveal good correspondence between the observed total cross sections and fragment-yield ratios, and the calculated ones. The model is also used to calculate the 4He/3He ratio from CNO + CNO collisions at 1 GeV/nucleon. Averaging over the mass numberof the CNO collision system, we calculate a ratio of 5.76 ± 0.52 ± 12%. A mass-independent thermal-model formula gives a ratio of only ≈ 1.5. The appreciable calculated production of 4He relative to 3He, as fragmentation products in atmospheric CNO collisions with 1 GeV/nucleon cosmic-ray primary CNO nuclei, has important implications for studies of atmospheric secondaries as background sources for space-based and balloon-borne light-fragment observations.
Generalized hydrodynamics and heat waves
Authors: Khayat R. E. , Eu Byung Chan
Published: April 2011

By using the evolution equations of generalized hydrodynamics we investigate heat-pulse propagation in a Lennard–Jones liquid contained in the annulus between two concentric cylinders at different temperatures. It is found that the heat pulse propagates as a wave of a finite speed when a composite fluid dynamic number [Formula: see text] that depends on the thermal conductivity and wall temperature ratio is above a critical value, but in the subcritical region the heat pulse propagates diffusively as if predicted by a parabolic differential equation with an infinite speed of propagation. Therefore the question of the hyperbolicity of the system of differential (evolution) equations used is mainly determined by the parameter [Formula: see text]. This implies that the hyperbolicity of evolution equations, i.e., the finiteness of pulse-propagation speed, cannot be the main reason for extending the thermodynamics of irreversible processes as believed by some authors in the literature. This study indicates that for a liquid of high thermal conductivity or a large temperature difference the Fourier law of heat conduction is inadequate for use in the description of the temporal evolution of heat and a suitable generalization of hydrodynamics is necessary. The generalized hydrodynamic equations presented in this and previous papers are examples for such a generalization.
Electron delocalization and transfer induced by a time-dependent potential: Exact treatment of a simple model — delocalization
Authors: Daré A.-M. , Lopez-Castillo J.-M. , Jay-Gerin J.-P.
Published: April 2011

We study the delocalization of a quantum particle in a one-dimensional, short-range (δ function), time-dependent potential. The energy spectrum of the emitted particle and the transition probability per unit time are obtained numerically by solving the Lippman–Schwinger equation using the discretized fractional calculus method of Lubich. An analytical calculation that follows the lines of the Keldysh–Faisal–Reiss treatment of the closely related problem of high-intensity laser-induced multi-photon ionization of atoms is also presented. As in this latter case, we observe an above-threshold ionization and a ponder-omotive shift associated with the emitted particle energy spectrum. The transition probability per unit time, as calculated analytically, is found to agree well with the numerical results for small enough perturbations. As the amplitude or the frequency of the excitation is varied, a feedback mechanism between the various ionization channels is observed.
Confining potential in momentum space
Authors: Norbury John W. , Kahana David E. , Maung Khin Maung
Published: April 2011

A method is presented for the solution in momentum space of the bound-state problem with a linear potential in r space. The potential is unbounded at large r leading to a singularity at small q. The singularity is integrable, when regulated by exponentially screening the r-space potential, and is removed by a subtraction technique. The limit of zero screening is taken analytically, and the numerical solution of the subtracted integral equation gives eigenvalues and wave functions in good agreement with position space calculations.
Elastic constants of potassium chloride
Authors: Kim Soon-Chul , Kwon T. H.
Published: April 2011

A localized model, based on the normal-mode frequencies of ions allowed to oscillate in an uniformly deformed crystal in a static potential field caused by all the other ions being assumed to be at rest in their mean positions, is used for calculating elastic constants of crystalline potassium chloride (KCl). The numerical results obtained are compared with available experimental data for elastic constants of crystalline KCl at atmospheric pressure. Calculated results for C11, C44 and C12 show reasonably good agreement with experimentally observed data.
Semiconductivity and optical interband transitions of CuV2O6 and Cu2V2O7
Authors: Benko F. A. , Koffyberg F. P.
Published: April 2011

CuV2O6 and Cu2V2O7 are low-mobility n-type semiconductors; at room temperature [Formula: see text]. From photoelectron-chemical measurements optical interband transitions are found at 2.02 and 3.15 eV for indium-doped CuV2O6, and at 1.87 and 2.88 eV for Cu2V2O7. In both materials the valence band edge is 6.9 eV below the vacuum level; a qualitative analysis of all data indicates that the upper valence band is made up mainly of oxygen-2p wave functions, as in V2O5.
Study of polymorphism and torsional motions in 3-chloro-4-methylaniline using 35Cl NQR (nuclear quadrupole resonance)
Authors: Roy S. K. , Amitha B. , Uchil J.
Published: April 2011

35Cl nuclear quadrupole resonance (NQR) in three polymorphic phases of 3-chloro-4-methylaniline is detected for the first time. Out of these, two phases (α and γ) are stable and the other (β) is found to be metastable. The β phase is found to transform to the stable γ phase with respect to time. The formation of the β and γ phases are discussed in terms of defects and strains. The temperature dependence of NQR lines in the range 77–292 K in all three phases is studied in detail. On the basis of a modified Bayer's theory the torsional frequencies and their temperature coefficients are computed.
Collision-induced absorption in cyclopropane (C3H6)
Authors: Dagg I. R. , Anderson A. , Smith W. , Reid P. J. , Joslin C. G. , Gray C. G.
Published: April 2011

We have measured the far-infrared absorption spectrum of cylopropane (C3H6) at frequencies up to 400 cm−1, at densities up to 5 amagat at 295 K and up to 16 amagat at 360 K, using a combination of Fourier-transform and laser techniques. (An amagat is defined as the density of a gas at N.T.P.). By studying the density-dependence of absorption, we have isolated the collisional component of the spectrum. This arises from pair dipole moments induced by the permanent quadrupole, octopole, and hexadecapole moments of the C3H6 molecule. To the extent that the intermolecular potential is isotropic, the induced spectrum can be expressed as the convolution of symmetric top free rotation spectra with translational spectra representing the relative motion of an interacting molecular pair. The former are calculated using expressions recently derived. For the latter we use information theory to provide a "least-biased" estimate based only on available information concerning the zeroth and second moments of the translational frequency spectrum, which can be calculated without approximation within the framework of equilibrium statistical mechanics. The result of these computations is a simple analytic expression for the absorption coefficient [Formula: see text], which is entirely free of adjustable parameters, and yet yields a good representation of the experimental results over most of the frequency range. Our results lend strong support to the theoretical values of the multipole moments calculated by other workers.
Neutrino electromagnetic scattering in astrophysics
Authors: Poon Alan W. , Waltham Christopher E.
Published: April 2011

We consider the electromagnetic scattering of neutrinos via their magnetic moment in astrophysical systems. We find that in the Sun the scattering processes flipping the neutrino from its left-handed state to its right-handed state are unimportant for all allowable values of the neutrino magnetic moment. However, considering these processes in the supernova SN1987A, we find that the upper limit of the neutrino magnetic moment to be in the order of 3 × 10−11 μB.
Scattering by a thin multicoated perfectly conducting spherical shell with a circular aperture
Authors: Said R. A. , Hamid M.
Published: April 2011

An analytic solution is presented for the problem of an infinitely thin perfectly conducting spherical shell with a circular aperture of arbitrary angle cut into the shell, filled with a dielectric, and coated by different thicknesses of spherical dielectric layers. The fields in all regions are expanded in terms of spherical wave functions and the boundary conditions of the continuity of the tangential fields at the dielectric–dielectric and dielectric–free-space boundaries are applied to express the expansion coefficients of the first dielectric layer in terms of the scattering coefficients. To approximate the modal expansion coefficients, the least-square error method is applied to the equations resulting from matching the fields through the aperture. Different numerical results for the simple case of a single coating layer are obtained in the form of amplitude patterns for the aperture and scattered fields versus angle as well as the backward- and forward-scattering cross sections for different loadings as functions of cavity size.
Hamiltonian dynamics of the general double sine-Gordon kinks
Authors: Zhang Lin , Huang Lin , Hu Shi-Ke
Published: April 2011

We present a complete Hamiltonian treatment of the internal oscillations of a solitary wave solution in the general double sine-Gordon system with n = 3. The exact stationary solution for the system is found. The frequencies and the ratio between the frequencies of the internal oscillations are shown, and agree with numerical results.
Parabolic periodic solutions of precipitation-modified ternary diffusion equations
Authors: Brechet Yves , Kirkaldy J. S.
Published: April 2011

Closed-form generalizations of Zener's binary solutions to the diffusion equations in one and two semi-inifite dimensions are found for the case where unstable dilute precipitation accompanies directed ternary diffusion. It has been argued elsewhere that instabilities caused by fine precipitates, subject to local conservation of the independent diffusion species and capillarity in a semi-infinite ternary medium, are evidenced by the appearance of a negative determinant of the effective diffusion matrix and a negative eigenvalue as in spinodal decomposition. In the unstable directed-diffusion planar case the eigenfunction corresponding to the negative coefficient is a spatially periodic Kummerian function of the parabolic coordinate [Formula: see text]. In the important asymptotic limit λ → ∞ this solution implies the exact Jablczynski-scaling relation for the time-independent position of the periodic precipitate bands, which is a well-known characteristic of the Liesegang phenomenon. This contrasts with the Belousov–Zhabotinskii instability where travelling waves are the norm. The cylindrical case exhibits an analogous character but is much richer in pattern, including rings, spirals of multifold character, and broken rings, all of which are observed. A free-boundary degeneracy as in the Saffman–Taylor problem is identified.
Two models in quantum cosmology
Authors: Krori K. D. , Purkayastha Anuradha Das
Published: April 2011

A study of two quantum-cosmological models is presented in this paper. These models are simpler than the Starobinsky model. However they exhibit some features very similar to those of the Starobinsky model.
Scale-invariant effective action with torsion
Authors: Kao W. F.
Published: April 2011

We considered a four-dimensional scale-invariant effective theory with a torsion field conformally coupled to a metric field. We find that the contribution from the torsion field is negligible in the evolution of the early universe. An exact solution is also obtained for k = 0 Friedmann–Robertson–Walker space in the vanishing cosmological constant limit. This solution is also a good approximation to k ≠ 0 spaces. Possible implications to the inflationary universe are also discussed.
Eigenvalue problem for tridiagonal matrices arising in the scattering-theory analysis of disordered conductors
Authors: Zuk Josef A.
Published: April 2011

The eigenvalue problem for a family of tridiagonal matrices arising in the scattering-theory analysis of the conductance in mesoscopic systems, and its fluctuations, is studied. The exactly solvable special cases are identified. For the general problem, qualitative characteristics of the spectrum are established, and approximate solutions for the eigenvalues are constructed. These comprise ones that are valid in the limit of large but finite matrix dimension, and those derived from a perturbation expansion around each of the exactly solvable cases.
The rotational analysis of the A1Π–X1Σ+ system of Si130Te
Authors: Gopal Sheila , Singh M. , Lakshminarayana G.
Published: April 2011

The emission spectrum of Si130Te was excited by microwave discharge (2450 MHz) in a sealed quartz tube. The A1Π–X1Σ+ band system (3100–3900 Å) (1 Å = 10−10 m) photographed under high resolution on a 10.6 m Ebert grating spectrograph. The rotational analysis of 32 bands was carried out, which led to the determination of the accurate vibrational and rotational constants. The rotational structure belonging to ν′ > 9 levels appear to be perturbed.
The voltage–current characteristics of a boundary layer arc
Authors: Au S. , Smy P. R. , Topham D. R. , Woods H. A.
Published: April 2011

The voltage–current characteristics of a boundary layer arc were measured over wide ranges of flow velocity (Ma 0.02–1.5) and current (10–100 A) by using three different experimental combinations. The arc is held in close contact with a solid surface because of the relative motion of the surrounding gas. The measured data show reasonable agreement with the predictions of a temperature-dependent Prandtl boundary layer model. Analysis of the saturation ion current from the arc to a Langmuir probe set in the solid surface shows that the inner surface of the arc lies very close to the surface as assumed in the theoretical model. A similar arc–flow–solid configuration arises in some circuit breakers, arc heaters, gas lasers, and even spark ignition devices. The ranges of current and flow velocities in these situations generally lie within the ranges covered by the results described in this paper.