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  • 1
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    Coherent potential approximation for strong-coupling superconducting transition-metal alloys (1974)
    Springer
    Details
    Publication Date: 1974-09-01
    Print ISSN: 0939-7922
    Electronic ISSN: 1431-5831
    Topics: Physics
    Published by Springer
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    PAPER CURRENT
  • 2
    Electronic Resource
    Electronic Resource
    Susceptibility of rare earth compounds in the intermediate valence state (1977)
    Springer
    The European physical journal 28 (1977), S. 213-224 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The thermodynamic potential of rare earth compounds in a mixed valent state is investigated by perturbation theoretical methods. Two types of contributions must be distinguished, the impurity terms and terms corresponding to interactions between different rare earth sites. For a large class of substances the latter are shown to be of minor importance. The susceptibility of the resulting theory is compared directly with the renormalization group calculations of Krishna-murthy, Wilson and Wilkins and with measured susceptibilities ofα-Ce, SmB6, YbAl3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01313044
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Coherent potential approximation for strong-coupling superconducting transition-metal alloys (1974)
    Springer
    The European physical journal 271 (1974), S. 229-234 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Within the coherent potential approximation (CPA) a theory for strong-coupling superconducting transition-metal alloys is developed. The configurational dependence of the selfenergy-part is discussed and, in analogy to McMillan, an expression forT c is derived for a singles band as well as for anΓ′25-band. The electron-phonon coupling constantλ occuring in this expression depends explicitly on: the average component density of states,N A (0) andN B (0), the electron-phonon matrix elements of the components, the difference of the atomic energy levels,δ, and the phonon Green's function at zero frequency. In the limit of the pure metal this expression reduces to that developed by Appel and Kohn. It is shown that the change of the phonon density of states in an alloy due to the atomic mass differences — which is very complicated — does not influence the value ofλ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01677928
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  • 4
    Electronic Resource
    Electronic Resource
    Simulating 2D Flows with Viscous Vortex Dynamics (2000)
    Springer
    Journal of statistical physics 101 (2000), S. 567-577 
    Details
    ISSN: 1572-9613
    Keywords: hydrodynamics ; Navier–Stokes equation ; turbulence ; Lamb vortex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Approximate solutions of the two-dimensional Navier–Stokes equation can be constructed as a superposition of viscous Lamb vortices. Requiring minimum deviation from the Navier–Stokes equation, one gets a set of ordinary differential equations for the positions, strength and width of the vortices. We calculate the deviation of the solution from the Navier–Stokes equation in the square norm. The time dependence of this error is determined and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026483521802
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  • 5
    Electronic Resource
    Electronic Resource
    Coherent potential approximation for nonmagnetic weak-coupling superconducting alloys. II (1974)
    Springer
    Journal of low temperature physics 15 (1974), S. 269-280 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Green's functions and correlation functions are calculated in a nonmagnetic superconducting alloy within the framework of the coherent potential approximation. Although, under alloying, the properties of the normal state will change more or less strongly, it is shown that certain superconducting properties will be very similar to those of the pure metal. These include the diverging density of states at frequencies equal to the order parameter Δ and the behavior of the correlation functions at very low frequencies and frequencies near 2Δ. The penetration depth of a magnetic field is calculated and can be a highly asymmetric function of the alloy concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00661186
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  • 6
    Electronic Resource
    Electronic Resource
    Coherent potential approximation for nonmagnetic weak-coupling superconducting alloys (1973)
    Springer
    Journal of low temperature physics 12 (1973), S. 595-600 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract With the aid of the Nambu formalism the coherent potential approximation (CPA) is applied to superconducting binary alloys of arbitrary composition. It will be shown that an approximation in which the order parameter Δ does not depend on the space variable leads to a generalized Abrikosov relation, simplifying the CPA equations considerably. This relation yields the BCS equation forT c , however, the density of states is determined by the CPA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00654960
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  • 7
    Electronic Resource
    Electronic Resource
    Self-consistent approximations for itinerant ferromagnetism below the phase-transition point (1971)
    Springer
    Journal of low temperature physics 4 (1971), S. 79-95 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The self-consistent and “conserving” (in particular the total spin is conserved) approximation scheme, developed in a previous paper for itinerant ferromagnetism, is extended to the region below the phase-transition point. The former general condition for the transformation properties of any approximate self-energy part with regard to infinitesimal transformations in spin space is applied to the case where the transformation is a finite rotation in spin space; these rotations correspond to rotations of the direction of the spontaneous magnetization which is fixed here by an infinitesimal auxiliary fieldH. This transformation property of the self-energy part ensures that the equations determining the corresponding Green's and correlation functions are covariant in form with respect to rotations ofH. Two examples are considered: the “Hartree-Fock” and the “particle-hole T-matrix” approximations for the contact interaction or Hubbard model. In the first example the resulting susceptibilities are shown to be causal response functions, provided the Stoner equation is fulfilled. In the second example the self-energy part and theT matrix are discussed for the two cases whereH is parallel and perpendicular to the axis of spin quantization. In fact, these expressions can be transformed into each other by means of the corresponding rotation matrix in spin space.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00628439
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  • 8
    Electronic Resource
    Electronic Resource
    The correlation functions near intermittency in a one-dimensional Piecewise parabolic map (1996)
    Springer
    Journal of statistical physics 83 (1996), S. 1199-1210 
    Details
    ISSN: 1572-9613
    Keywords: Weak intermittency ; chaos ; phase transition ; correlation function ; scaling function ; crossover behavior ; critical slowing down
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Piecewise parabolic maps constitute a family of maps in the fully developed chaotic state and depending on a parameter that can be smoothly tuned to a weakly intermittent situation. Approximate analytic expressions are derived for the corresponding correlation functions. These expressions produce power-law decay at intermittency and a crossover from power-law decay to exponential decay below intermittency. It is shown that the scaling functions and the exponent of the power law depend on the kind of the correlations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02179558
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