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  • 1
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    Wiley
    In:  Hoboken, NJ, 633 pp., Wiley, vol. 16B, no. 2, pp. 125-169, (ISBN 0-471-26610-8)
    Publication Date: 2003
    Keywords: Textbook of mathematics ; Data analysis / ~ processing ; Modelling ; software ; manual ; computer ; algebra ; symbolic ; mathematics
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 7641-7647 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Transition inverse temperatures (or Γ values) at the fluid–solid phase boundary of Yukawa systems near the one-component-plasma (OCP) limit have been evaluated by molecular dynamics simulations. These values are systematically smaller than those obtained in an earlier study by Farouki and Hamaguchi [J. Chem. Phys. 101, 9885 (1994)]. The discrepancy is attributed to the fact that, in the earlier study, the harmonic entropy constants were approximated by that of the OCP, whereas the new results are based on more accurate harmonic entropy constants obtained from lattice-dynamics calculations. The new molecular dynamics simulations also confirm that the bcc–fcc phase transition curve is in good agreement with that of the quasiharmonic theory in the regime κ≤1.4, where κ is the ratio of the Wigner–Seitz radius to the Debye length. Examples of Yukawa systems include dusty plasmas and colloidal suspensions. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 11 (1999), S. 905-914 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Vortex-in-cell simulations that numerically integrate the 2D Euler equations are compared directly to experiments on magnetized electron columns [K. S. Fine, A. C. Cass, W. G. Flynn, and C. F. Driscoll, "Relaxation of 2D turbulence to vortex crystals," Phys. Rev. Lett. 75, 3277 (1995)], where turbulent flows relax to metastable vortex crystals. A vortex crystal is a lattice of intense small diameter vortices that rotates rigidly in a lower vorticity background. The simulations and experiments relax at the same rates to vortex crystals with similar vorticity distributions. The relaxation is caused by mixing of the background by the intense vortices: the relaxation rate is peaked when the background circulation is 0.2–0.4 times the total circulation. Close quantitative agreement between experiment and simulation provides strong evidence that vortex crystals can be explained without incorporating physics beyond 2D Euler theory, despite small differences between a magnetized electron column and an ideal 2D fluid. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 12 (2000), S. 2397-2412 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The inviscid damping of an asymmetric perturbation on a two-dimensional circular vortex is examined theoretically, and with an electron plasma experiment. In the experiment, an elliptical perturbation is created by an external impulse. After the impulse, the ellipticity (quadrupole moment) of the vortex exhibits an early stage of exponential decay. The measured decay rate is in good agreement with theory, in which the perturbation is governed by the linearized Euler equations. Often, the exponential decay of ellipticity is slow compared to a vortex rotation period, due to the excitation of a quasimode. A quasimode is a vorticity perturbation that behaves like a single azimuthally propagating wave, which is weakly damped by a resonant interaction with corotating fluid. Analytically, the quasimode appears as a wave packet of undamped continuum modes, with a sharply peaked frequency spectrum, and it decays through interference as the modes disperse. When the exponential decay rate of ellipticity is comparable to the vortex rotation frequency, the vorticity perturbation does not resemble a quasimode; rather, it is rapidly dominated by spiral filaments. Over longer times, linear theory predicts algebraic decay of ellipticity; however, nonlinear oscillations of ellipticity emerge in the experiment before a transition to algebraic decay would occur. © 2000 American Institute of Physics.
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  • 5
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experiments and theory on collisional diffusion and viscosity in quiescent single-species plasmas demonstrate enhanced transport in the two-dimensional (2D) bounce-averaged regime, limited by shear in the plasma rotation. For long plasma columns, the measured diffusion agrees quantitatively with recent theories of three-dimensional long-range E×B drift collisions, and is substantially larger than predicted for classical velocity-scattering collisions. For short plasmas, diffusion is observed to be enhanced by Nb, the number of times a thermal particle bounces axially before being separated by shear. Equivalently, recent theory in the 2D bounce-averaged regime shows how diffusion decreases with increasing shear, generalizing the zero-shear perspective which gives Bohm diffusion. Viscosity is similarly enhanced in the 2D regime, but there is presently only qualitative agreement with theory. These results apply to both non-neutral and neutral plasmas, and provide the first rigorous analysis of shear reduction of transport in a paradigmatic system. © 2002 American Institute of Physics.
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  • 6
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Enhanced cross-magnetic-field diffusion of test particles in pure ion plasmas has been measured. The ion plasma is contained in a Penning-Malmberg trap for weeks near thermodynamic equilibrium, characterized by rigid rotation and uniform density and temperature. Plasma expansion and loss is suppressed by a "rotating wall" technique, i.e., a weak electrostatic potential rotating faster than the plasma. Test particle transport is then measured even though there is zero net transport, in a regime where neutral collisions are negligible. The observed test particle transport is diffusive, i.e., proportional to the gradient of the test particle concentration. The measured diffusion coefficients scale as nT−1/2B−2 over a range of 40 in density, 50 in temperature, and 5 in magnetic field. This diffusion is about ten times greater than predicted by classical collisional theory, which describes velocity-scattering collisions with impact parameters ρ(approximately-less-than)rc. The enhanced transport is thought to be due to non-velocity-scattering "E×B drift" collisions with rc〈ρ(approximately-less-than)λD. Initial estimates of diffusion due to these long-range collisions are three times less than the measurements, and substantial theory questions remain. © 1997 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 295-324 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: When a single-species plasma is confined in a harmonic Penning trap at cryogenic temperature, the thermal equilibrium is approximately a uniform density spheroid (ellipsoid of revolution). Normal modes corresponding to quadrupole excitations of this plasma have recently been measured. In this paper, nonlinear equations of motion are derived for these quadrupole oscillations. For large amplitudes, the oscillations deform a spheroidal plasma into a triaxial ellipsoid with time-dependent shape and orientation. The integrals of the motion are found and the cylindrically symmetric finite-amplitude oscillations of a spheroid are studied. An analysis of all possible ellipsoidal equilibria is also carried out. New equilibria are discovered which correspond to finite-amplitude versions of the noncylindrically symmetric linear quadrupole oscillations. The equilibria are shown to fall into two classes in which the ellipsoids are either tilted or aligned with respect to the magnetic field. Some of these equilibria have densities well above the Brillouin limit.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 274-277 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The regime of validity of nonlinear gyrokinetic equations is extended to cover uniformly both the usual drift-kinetic and gyrokinetic regimes through the use of an expansion in the parameter ε∼(ρ/λ⊥)e(φ−v(parallel) Az/c)/T. Here, ρ is the gyroradius, λ⊥ is the scale length of the electrostatic and parallel magnetic potentials φ and Az, c is the speed of light, and T is the temperature. This is made possible by a preparatory split of the potentials into gyrophase-dependent and independent parts. For nonlinear fluctuations saturated at mixing-length levels (e.g., with eφ/T∼λ⊥ /L, where L is the equilibrium scale length), ε is of order ρ/L for all scales λ⊥ ranging from ρ to L, and is therefore small in plasmas of fusion interest.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 43 (2002), S. 1063-1073 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Among the multiplication operators on weighted Bergman Hilbert spaces are those where the multiplying function (operator symbol) depends only on the angular polar coordinate in the unit disk: we call these "angle operators." As these Hilbert spaces carry a CCR representation unitarily equivalent to the Schrödinger representation, angle operators are associated with quantum phase in the same way as are Toeplitz operators, for example. We determine the matrix elements of the angle operators with respect to the natural orthonormal basis on each of these spaces, and also with respect to the appropriate family of coherent states. By using a method of comparison with the corresponding results for Toeplitz operators, asymptotic expressions for the expectations and variances in these two families of states are obtained for the angle operators whose symbols are the polar angle function and its two complex exponentials. Notable is the fact that the asymptotic limit of the variance of the polar angle operator in the natural basis family is π2/3, which many authors take to be a requirement for a quantum phase operator. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 38 (1997), S. 3238-3262 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: We consider *-representations of the unital complex *-algebra generated by the identity and two elements, α and ν, with ν=ν* and one relation, αν−να=α, the ultra-commutation relations (ucr). In general, we do not impose any commutation relation between α and α*. This is a very general scheme, encompassing many important physical examples, inter alia: the ccr, car, q-deformed bosons and fermions. The representations of interest in physics have a diagonal number operator π(ν) whose spectrum is contained in the positive integers (together with some other technical conditions). Our principal result is that every *-representation in this class is completely determined, up to unitary equivalence, by the sequence of numbers [n+1]=|〈Ωn+1,π(α+)Ωn〉|2 for n≥0, with [0]=0. Here Ωn is the normalized eigenvector of π(ν) corresponding to the eigenvalue n if the dimension of that eigenspace is 1. If the carrier Hilbert space is infinite dimensional, this representation is irreducible if and only if [n]〉0 for n≥1. Finally, we consider spatial representations of some of these representations by kernels and differential operators. © 1997 American Institute of Physics.
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