In the last 30 days

• Open/close Electromagnetic potentials without gauge transformations

  A Chubykalo et al 2011 Phys. Scr. 84 015009 Tag this article

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  In this paper, we show that the use of the Helmholtz theorem enables the derivation of uniquely determined electromagnetic potentials without the necessity of using gauge transformation. We show that the electromagnetic field comprises two components, one of which is characterized by instantaneous action at a distance, whereas the other propagates in retarded form with the velocity of light. In our attempt to show the superiority of the new proposed method to the standard one, we argue that the action-at-a-distance components cannot be considered as a drawback of our method, because the recommended procedure for eliminating the action at a distance in the Coulomb gauge leads to theoretical subtleties that allow us to say that the needed gauge transformation is not guaranteed. One of the theoretical consequences of this new definition is that, in addition to the electric E and magnetic B fields, the electromagnetic potentials are real physical quantities. We show that this property of the electromagnetic potentials in quantum mechanics is also a property of the electromagnetic potentials in classical electrodynamics.

• Open/close Foundations of quantum mechanics?

  Göran Lindblad 2011 Phys. Scr. 84 018501 Tag this article

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  Does quantum mechanics have unsolved foundational problems? Is there a dividing line between the quantum and classical descriptions of the world? In this paper, I give an elementary introduction to the mathematical aspects of quantum and classical models which have prompted such questions.

• Open/close From the conservation laws to the Hamiltonian structures of discrete soliton systems

  Jian-bing Zhang et al 2011 Phys. Scr. 84 015001 Tag this article

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  We describe an approach to investigate the Hamiltonian structures of discrete soliton systems, which is deduced from the relation between the conservation laws and the Hamiltonian structures. As to its applications, the Toda lattice, the Blaszak–Marciniak lattice and the Blaszak–Marciniak (II) are discussed.

• Open/close Accurate analytic approximation to the nonlinear pendulum problem

  M Turkyilmazoglu 2011 Phys. Scr. 84 015005 Tag this article

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  This paper is concerned with the accurate analytic solution of the nonlinear pendulum differential equation. Instead of the traditional Taylor series or asymptotic methods, the homotopy analysis technique is used, which does not require a small perturbation parameter or a large asymptotic parameter. It is shown here that such a method is extremely powerful in gaining the pendulum solution in terms of purely trigonometric cosine functions. The obtained explicit analytical expressions for the frequency, period and displacement generate results that compare excellently with the numerically computed ones for moderate as well as sufficiently high values of the initial amplitudes. For larger initial amplitudes close to 180° Padé approximants of the found series solutions lead to fairly accurate results whose relative errors as compared with the exact values are less than 1%.

• Open/close Self-Affine Fractals and Fractal Dimension

  Benoit B Mandelbrot 1985 Phys. Scr. 32 257 Tag this article

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  Evaluating a fractal curve's "approximate length" by walking a compass defines a "compass exponent." Long ago, I showed that for a self-similar curve (e.g., a model of coastline), the compass exponent coincides with all the other forms of the fractal dimension, e.g., the similarity, box or mass dimensions. Now walk a compass along a self-affine curve, such as a scalar Brownian record B( t). It will be shown that a full description in terms of fractal dimension is complex. Each version of dimension has a local and a global value, separated by a crossover. First finding: the basic methods of evaluating the global fractal dimension yield 1: globally, a self-affine fractal behaves as it if were not fractal. Second finding: the box and mass dimensions are 1.5, but the compass dimension is D = 2. More generally, for a fractional Bownian record B _H ( t), (e.g., a model of vertical cuts of relief), the global fractal dimensions are 1, several local fractal dimensions are 2- H, and the compass dimension is 1/ H. This 1/ H is the fractal dimension of a self-similar fractal trail, whose definition was already implicit in the definition of the record of B _H ( t).

• Open/close The Lindhard Function and the Teaching of Solid State Physics

  Henrik Smith 1983 Phys. Scr. 28 287 Tag this article

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• Open/close An ECR ion source-based low-energy ion accelerator: development and performance

  A N Agnihotri et al 2011 Phys. Scr. 2011 014038 Tag this article

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  Electron cyclotron resonance (ECR) ion sources produce low-energy, highly charged ions. A new 14.5 GHz ECR-based low-energy ion accelerator facility has been developed. The ion source involves a plasma chamber ('supernanogan') surrounded by permanent magnets that provide a suitable magnetic field. The entire assembly including the ion source and the analyzing magnet is mounted on a 400 kV deck. A LabVIEW-based command and control system has been developed for the beamline. In addition, wireless communication has been installed to operate the machine in high voltage. The charge state distribution of several ions (He, N ₂, O ₂, Ne, Ar and Xe) has been measured. For Ar and Xe, the maximum charge states measured were 16 ⁺ and 29 ⁺, respectively. A direct x-ray measurement for plasma diagnostics was also initiated.

• Open/close Head-on collision of ion-acoustic solitary waves in a plasma with a q-nonextensive electron velocity distribution

  Parvin Eslami et al 2011 Phys. Scr. 84 015504 Tag this article

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  In this paper, the characteristics of the head-on collision of ion-acoustic solitary waves (IASWs) in the collisionless magnetic-field-free plasma consisting of cold ions, nonextensive electrons and thermal positrons are discussed using the extended Poincaré–Lighthill–Kuo method. Two Kortewege–de Vries equations for solitary waves are derived and the analytical phase shifts after the head-on collision of two solitary waves are also obtained. The effects of the electron nonextensive distribution ( q-parameter) on the phase shifts of both the colliding solitary waves are studied. It is found that the presence of nonextensive electrons plays a significant role in the collision of IASWs.

• Open/close Perturbation of dispersive topological solitons

  Stephen Johnson and Anjan Biswas 2011 Phys. Scr. 84 015002 Tag this article

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  This paper studies the dynamics of topological solitons in the cases of the dispersive sine-Gordon equation, the double sine-Gordon equation and the triple sine-Gordon equation. The adiabatic dynamics of the soliton velocity are also obtained for each case in the presence of perturbation terms.

• Open/close Viscoelastic Acoustic Response of Layered Polymer Films at Fluid-Solid Interfaces: Continuum Mechanics Approach

  M V Voinova et al 1999 Phys. Scr. 59 391 Tag this article

  Article References Full text PDF (155 KB)

  We have derived the general solution of a wave equation describing the dynamics of two-layer viscoelastic polymer materials of arbitrary thickness deposited on solid (quartz) surfaces in a fluid environment. Within the Voight model of viscoelastic element, we calculate the acoustic response of the system to an applied shear stress, i.e. we find the shift of the quartz generator resonance frequency and of the dissipation factor, and show that it strongly depends on the viscous loading of the adsorbed layers and on the shear storage and loss moduli of the overlayers. These results can readily be applied to quartz crystal acoustical measurements of the viscoelasticity of polymers which conserve their shape under the shear deformations and do not flow, and layered structures such as protein films adsorbed from solution onto the surface of self-assembled monolayers.