Showing papers in "Canadian Journal of Physics in 2006"

Energy levels for the stable isotopes of atomic helium(4He I and 3He I)

Abstract: We calculate very accurate ab initio ionization energies for both 4He I and 3He I as well as the isotope shifts for n = 1 to 10, L = 0 to 7 and combined these with precise laboratory data to produc...

Boundary-layer flow of a micropolar fluid on a continuous moving or fixed surface

Abstract: The present paper deals with the analysis of boundary-layer flow of a micropolar fluid on a fixed or continuous moving plane surface. Both parallel and reverse moving surfaces to the free stream are considered. The resulting system of nonlinear ordinary differential equations is solved numerically using the Keller-box method. Numerical results are obtained for skin friction coefficient, local Nusselt number, velocity, angular velocity, and temperature profiles. The results indicate that the effect of the material parameter on skin friction and heat transfer depends on the velocity ratio of the plate and the fluid.PACS No.: 47.15.Cb

Onset of convection in a viscoelastic-fluid-saturated sparsely packed porous layer using a thermal nonequilibrium model

Abstract: A linear stability analysis is carried out to study viscoelastic fluid convection in a sparsely packed horizontal porous layer heated from below. The viscoelastic fluid flow in the porous medium is modeled by using a modified Brinkman–Lapwood-extended Darcy model with the fluid viscosity different from the effective viscosity, which accounts for the viscoelastic properties and frictiondue to macroscopic shear. Besides, a two-field model for temperature each representing the solid and fluid phases separately is employed. The conditions for the occurrence of direct and Hopf bifurcations of the thermal convective instability are obtained analytically. It is shown that Hopf bifurcation occurs only if the retardation to relaxation-time ratio, Λ, is less than unity and the elasticity parameter, Γ, exceeds a threshold. Further, the effects of the viscoelastic parameters and the thermal nonequilibrium on the onset of convection are analyzed in detail.PACS No.: 47.55.–pb

The one-dimensional hydrogen atom revisited

Abstract: The one-dimensional Schrodinger hydrogen atom is an interesting mathematical and physical problem for the study of bound states, eigenfunctions, and quantum-degeneracy issues This one-dimensional

Attosecond science and technology

Abstract: Attosecond technology is a radical departure from all the optical (and collision) technology that preceded it. It merges optical and collision physics. The technology opens important problems in each area of science for study by previously unavailable methods. Underlying attosecond technology is a strong laser field. It extracts an electron from an atom or molecule near the crest of the field. The electron is pulled away from its parent ion, but is driven back after the field reverses. It can then recollide with its parent ion. Since the recolliding electron has a wavelength of about 1 A, we can measure Angstrom spatial dimensions. Since the strong time-dependent field of the light pulse directs the electron with subcycle precision, we can control and measure attosecond phenomena. PACS Nos.: 33.15.Mt, 33.80.Rv, 39.90.+d, 42.50.Hz, 42.65.Ky

The Pioneer anomaly: seeking an explanation in newly recovered data

Abstract: The Pioneer 10 and 11 spacecraft yielded very accurate navigation in deep space that was, however, limited by a small, anomalous frequency drift of their carrier signals received by the radio-track...

Electrodynamics of a magnet moving through a conducting pipe

Abstract: The popular demonstration involving a permanent magnet falling through a conducting pipe is treated as an axially symmetric boundary-value problem. Specifically, Maxwell's equations are solved for an axially symmetric magnet moving coaxially inside an infinitely long, conducting cylindrical shell of arbitrary thickness at nonrelativistic speeds. Analytic solutions for the fields are developed and used to derive the resulting drag force acting on the magnet in integral form. This treatment represents a significant improvement over existing models, which idealize the problem as a point dipole moving slowly inside a pipe of negligible thickness. It also provides a rigorous study of eddy currents under a broad range of conditions, and can be used for magnetic braking applications. The case of a uniformly magnetized cylindrical magnet is considered in detail, and a comprehensive analytical and numerical study of the properties of the drag force is presented for this geometry. Various limiting cases of interest...

The asymptotic iteration method for the angular spheroidal eigenvalues with arbitrary complex size parameter c

Abstract: The asymptotic iteration method is applied to calculate the angular spheroidal eigenvalues (c) with arbitrary complex size parameter c. It is shown that the numerical results obtained for (c) are all in excellent agreement with the available published data over the full range of parameter values m, and c. Some representative values of (c) for large real c are also given.PACS No.: 02.70.–c.

The standard cosmological model

Abstract: The Standard Model of Particle Physics (SMPP) is an enormously successful description of high-energy physics, driving ever more precise measurements to find "physics beyond the standard model", as

A cosmology with variable c

Abstract: A new varying-c cosmological model, constructed using two additional assumptions, which was introduced in our previous work, is briefly reviewed and the dynamic equation of the model is derived distinctly from a semi-Newtonian approach. The results of this model, using a term and an extra energy-momentum tensor, are considered separately. It is shown that the Universe began from a hot Big Bang and expands forever with a constant deceleration parameter regardless of its curvature. Finally, the age, the radius, and the energy content of the Universe are estimated and some discussion about the type of the geometry of the Universe is provided. PACS Nos.: 98.80.Bp, 98.80.Jk

Fast-ion-beam laser-induced-fluorescence measurements of spontaneous-emission branching ratios and oscillator strengths in Sm II

Abstract: We measured the spontaneous-emission branching ratios of 69 levels in Sm II selectively populated via single-frequency laser excitation of a 10 keV ion beam. The levels studied had term energies up to 29 600 cm–1, and decay branches with spontaneous emission in the range 250–850 nm were detected. The experimental accuracy was in the range of 10%. We used these branching ratios along with our previously determined radiative lifetimes to infer transition probabilities and oscillator strengths for 608 transitions in the wavelength range 363–771 nm, which are useful for stellar abundance determinations.PACS Nos.: 32.70.Cs, 95.30.Ky

The effects of temperature, humidity, and barometric pressure on short-sprint race times

Abstract: A numerical model of 100 m and 200 m world class sprinting performances is modified using standard hydrodynamic principles to include effects of air temperature, pressure, and humidity levels on ae...

On local-hidden-variable no-go theorems

Abstract: The strongest attack against quantum mechanics came in 1935 in the form of a paper by Einstein, Podolsky, and Rosen. It was argued that the theory of quantum mechanics could not be called a complet...

Mesure des propriétés diélectriques du béton par une large sonde coaxiale à terminaison ouverte

Abstract: We present nondestructive measurements of dielectric properties of concrete and mortar. The measures are made using a coaxial probe with a 32.5 mm open end, engineered specially for this work. The ...

Nuclear spectroscopy in the chaotic domain: level densities

Abstract: In heavy nuclei, the structure generating the slow-neutron resonance spectrum extends downward in energy to ~(1–2) MeV excitation and, of course, upward as well until particle emission becomes significant, thereby generating an Embedded Gaussian Orthogonal Ensemble (EGOE) spectrum built on a secular mean-density function. In this extended chaotic domain, principles and methods for the calculation of one-point quantities (e.g., level densities, spin-cutoff factors, occupancies, etc.,) have been well developed during the last several years. The economy and the resultant generic forms follow from the dominance of unitary symmetries, central limit theorems, and quantum chaos. In this paper, techniques used for level densities are illustrated by a detailed study of several heavy nuclei, the input data being taken from the observed low-lying spectrum and the far-separated neutron-resonance spectrum, this in itself saying much about long-range spectral rigidity. Explicit forms for the interacting particle state ...

Is entanglement entropy proportional to area

Abstract: It is known that the entanglement entropy of a scalar field, found by tracing over its degrees of freedom inside a sphere of radius , is proportional to the area of the sphere (and not its volume). This suggests that the origin of black-hole entropy, also proportional to its horizon area, may lie in the entanglement between the degrees of freedom inside and outside the horizon. We examine this proposal carefully by including excited states, to check probable deviations from the area law.PACS Nos.: 04.60.–m, 04.62, 04.70.–s, 03.65.Ud

Supersymmetric large extra dimensions and the cosmological constant problem

Abstract: This article briefly summarizes and reviews the motivations for — and the present status of — the proposal that the small size of the observed Dark Energy density can be understood in terms of the dynamical relaxation of two large extra dimensions within a supersymmetric higher dimensional theory.PACS Nos.: 31.15.Pf, 31.30.Jv, 32.10.Hq

On Stokes' problem for the flow of a third-grade fluid induced by a variable shear stress

Abstract: The flow of an incompressible third-grade fluid over an infinite wall is considered. The flow is due to a variable shear stress. Both the series and the numerical solutions of the nonlinear partial-differential equation resulting from the momentum equation are obtained. Effects of non-Newtonian parameters on the flow phenomena are analyzed. It is found that with an increase in second-grade parameter and third-grade parameter, the velocity decreases and thus, the boundary-layer thickness increases.PACS No.: 47.15.cb

Numerical simulations of a viscous-fingering instability in a fluid with a temperature-dependent viscosity

Abstract: We have performed numerical simulations of the flow of hot glycerine as it displaces colder, more viscous glycerine in a radial Hele–Shaw cell. We find that fingering occurs for sufficiently high i...

Electrons in a box: Thomas–Fermi solution

Abstract: The Thomas-Fermi density distribution of N electrons located inside a box is obtained. This system models some aspects of the structure of the new artificial atoms or quantum dots fabricated using present semiconductor technology. The three-dimensional solutions are obtained by means of a perturbative series, using a convenient dimensionless parameter characteristic of the size of the box and the electron number. The explicit analytic form for the first two terms of the series is derived. PACS No.: 71.10.Ca

Long tipping times of a quantum rod

Abstract: We calculate the tipping time of a quantum rod that has a height several times that of the edge length of its square base. We use an expression for the tipping time that has heuristic value, and gives the average time at which, upon measurement, the initially balanced rod is found to tip. We use two methods to calculate the tipping time. One method is to examine the "late time" behaviour of the quantum state of the center of mass of the rod by using an equation that has the form of the time-independent Schrodinger equation except that it involves a "complex energy." The other method uses energy resonances in the eigenstates of the Hamiltonian to determine the tipping time. We use the well-known Wentzel–Kramers–Brillouin approximation to calculate the energy eigenstates. With these methods, we obtain expressions for the tipping time that are valid for very long tipping times. PACS Nos.: 03.65.–w, 03.65.Xp

Probabilistic remote preparation of a three-atom Greenberger–Horne–Zeilinger class state via cavity quantum electrodynamics

Abstract: We present two schemes for remotely preparing a three-atom Greenberger–Horne–Zeilinger class state via entanglement swapping in cavity quantum electrodynamics. We show that each of our schemes can be achieved probabilistically by means of separate atomic measurements with the choice of an appropriate atom-cavity field interaction time.PACS Nos.: 03.67–a, 03.67.Lx, 42.50.Dv

Aspects of brane-antibrane inflation

Abstract: Je decris un mecanisme dynamique pour solutionner le probleme d'ajustement fin en inflation brane-antibrane. En inflation avec des piles de branes et d'antibranes, les branes peuvent etre naturellement piegees dans un minimum metastable du potentiel. Comme les branes quittent ce minimum par effet tunnel, la forme du potentiel change, le minimum devenant moins profond. Eventuellement, le minimum disparait et les branes restantes roulent lentement parce que le potentiel est essentiellement plat. Je montre que meme avec un petit nombre de branes, il y a une bonne chance d'obtenir suffisamment d'inflation. La variation (running) du parametre spectral est correlee avec la pente d'une facon qui permet un test du modele pour de futures experiences CMB.

Star-quantization of an infinite wall

Abstract: In deformation quantization (a.k.a. the Wigner–Weyl–Moyal formulation of quantum mechanics), we consider a single quantum particle moving freely in one dimension, except for the presence of one infinite potential wall. Dias and Prata pointed out that, surprisingly, its stationary-state Wigner function does not obey the naive equation of motion, i.e., the naive stargenvalue (*-genvalue) equation. We review our recent work on this problem that treats the infinite wall as the limit of a Liouville potential. Also included are some new results: (i) we show explicitly that the Wigner-Weyl transform of the usual density matrix is the physical solution, (ii) we prove that an effective-mass treatment of the problem is equivalent to the Liouville one, and (iii) we point out that self-adjointness of the operator Hamiltonian requires a boundary potential, but one apparently different from that proposed by Dias and Prata. PACS Nos.: 03.65.–w, 03.65.Ca, 03.65.Ge

Theoretical study with rovibrational and electronic transition moment calculation of the ion LiCs

Abstract: For the molecular ion LiCs+ the potential energy are calculated for the 39 lowest molecular states of symmetries 2Σ+, 2Π, 2Δ, and Ω = 1/2, 3/2, 5/2. Using an ab initio method, the calculation is based on nonempirical pseudopotentials and parameterized -dependent polarization potentials. Gaussian basis sets are used for both atoms and spin-orbit effects are taken into account. The spectroscopic constants for 20 states are calculated by fitting the calculated energy values to a polynomial in terms of the internuclear distance r. Through the canonical functions approach, the eigenvalue Ev, the abscissas of the corresponding turning points (rmin and rmax), and the rotational constants Bv are calculated for up to 44 vibrational levels for four bound states. Using the same approach the dipole moment functions, the corresponding matrix elements, and the transition dipole moments are calculated for the bound states (1)2Σ+, (2)2Σ+, and (1)2Π. The comparison of the present results with those available in literature...

Tools for laser spectroscopy: The design and construction of a Faraday isolator

Abstract: We discuss the design and construction of a Faraday isolator for diode laser spectroscopy using commercially available components. The design involves modelling the magnetic field of an assembly of...

Characterizing flat-top laser beams using standard beam parameters

Abstract: We examine the correspondence between various models describing flat-top laser beam profiles using two standard parameters; namely, the M2 factor and the kurtosis parameter. Numerical expressions for M2, based on the second moment of the beam irradiance distribution in the near and far fields and for the kurtosis parameter, k, based on the fourth moment at the near field, are obtained. Plots of k in the near field versus M2 demonstrate the similarities between the different analytical models used to describe flat-top profiles. Using the Pade approximation, a relationship between k and M2, a new reference formula, is derived that predicts the values of M2 to within less than a percent for these flattened beams. This method is then extended to define numerical expressions relating the beam parameters (i.e., M2 and k) and the parameters describing the beam characteristic in each analytical model (model parameters). The results obtained using the Pade method are used to describe the output beam profiles for a...

The epistemic view of quantum states and the ether

Abstract: The idea that the wave function represents information, or knowledge, rather than the state of a microscopic object has been held to solve foundational problems of quantum mechanics. Realist interp...

Evidence of strong two-particle and three-particle dynamical correlation in compound multiplicity distribution in nucleus-nucleus interactions at 4.5 AGeV

Abstract: This paper reports an investigation of two- and three-particle dynamical correlation in multiparticle production processes in terms of compound multiplicity (proton and pion) distributions. The data have been taken from 24Mg–AgBr and 12C–AgBr interactions at 4.5 AGeV. The experimental results are compared with those of Monte Carlo simulated events, assuming an independent emission of the compound multiplicity. The data exhibit strong two- and three-particle correlation in both forward and backward hemispheres in emission angle space for both data sets. PACS Nos.: 25.75–q, 24.60 Ky

When is the lowest order WKB quantization exact

Abstract: First, two conditions are specified for the lowest order Wentzel-Kramers- Brillouin quantization rule to yield exact results. These rules are related to the periodic orbit decomposition of the quantum density of states. This approach is then applied to supersymmetric quantum mechanics. It leads to a new derivation of the result that shape- invariant potentials give exact results when the classical action is calculated with the square of the super potential, but without the Maslov index or the Langer correction.