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  • 1985-1989  (6)
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  • 1
    Electronic Resource
    Electronic Resource
    Orthogonalization of function spaces in the resonating group model (1985)
    Springer
    The European physical journal 321 (1985), S. 581-588 
    Details
    ISSN: 1434-601X
    Keywords: 24.10.−i ; 21.60.Gx
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A coupled-channel resonating group equation for orthogonal channel spaces is derived. It follows from the common resonating group equation by a recursion relation. The recursion extracts from higher channels all overlaps with lower channels, such that the higher channels become corrections to the lower ones. A physically meaningful definition of elimination potentials becomes possible. The new coupled channel resonating group equation allows the derivation ofphysical effective potentials by eliminating small corrections, only. It also allows the derivation oftechnical potentials, i.e. potentials with an unphysical off-shell behaviour, when the dominant part of the equation is eliminated. A numerical example demonstrates that linear dependence of the test function space is not harmful to the new equation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01432433
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Orthogonalization of channel spaces in the quark resonating group model (1986)
    Springer
    Few body systems 1 (1986), S. 37-45 
    Details
    ISSN: 1432-5411
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A recently developed coupled-channel resonating group method with orthogonalized function spaces is tested. As test example a six-quark three-channel resonating group model is used. The channels are theNN-, ΔΔ- andCC- (“hidden colour”) channels. In earlier calculations without orthogonalization of channel spaces the relative motion function of theNN-channel had a node in theS-wave at approximately 0.5 fm. In the new treatment, in which the ΔΔ- andCC-channels are only orthogonal corrections to theNN-channel, this node is no longer present. The newNN wave function is very similar to the one of the single-channel approximation. Thus, in the one- and three-channel approximation, we consistently find that the six-quark resonating group model does not support the notion of a short-distance node in theNN wave function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01075290
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Off-shell behaviour of theN-N interaction in a six-quark resonating group model of the deuteron (1988)
    Springer
    Few body systems 5 (1988), S. 45-58 
    Details
    ISSN: 1432-5411
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Two different 6-quark resonating group models of the deuteron are investigated to study the off-shell property of theN-N interaction. In the first model the quarks interact by a central one-gluon-exchange potential plus confinement potential. The meson-exchange contribution to then-p potential is simulated by a central GaussianN-N potential. In the second model the quarks interact by one-gluon-and one-pion-exchange potentials (central and noncentral) plus confinement potential. A small additional “σ”-exchange potential between neutron and proton binds the deuteron at the correct energy. Several off-shell variants of the two resonating group models are compared with each other by analyzing their elastic electron scattering cross sections. It is found that the standard renormalized version of the resonating group model yields potentials and wave functions that may be considered physical within the limitations of the model. Unitary off-shell transformations, which modify potentials and wave functions in any sizeable way, lead to a disagreement between the charge distribution predicted by the model via analysis of electron scattering and the charge distribution following from the microscopic quark distribution. Both of the 6-quark models support a soft repulsive core of the tripletn-p potential with a core height of around 900 MeV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01351268
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Formation of clusters in the nuclear surface (1988)
    Springer
    Few body systems 5 (1988), S. 107-115 
    Details
    ISSN: 1432-5411
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An operator formalism is constructed which allows one to calculate a movie of nuclear density plots showing the linear oscillation of two chosen fragments (clusters) in a given ground state or virtual state of a nucleus. The main ingredients of the formalism are the projection of a nuclear wave function onto a chosen antisymmetrized cluster decomposition, and the knowledge that a quantum mechanicalL=0 motion is a linear motion averaged over angles. The formalism is tested and results are discussed in the well-known cases of a shell-model description and a resonating-group-model description of8Be. It is seen that two α-clusters appear even in the surface of the compact harmonic-oscillator shell model ground-state. They are formed with higher probability in the resonating-group-model description of the more realistic8Be virtual state at 92 keV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01079582
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    The two- and three-cluster fish bone model with saturation (1985)
    Springer
    The European physical journal 320 (1985), S. 399-404 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The two- and three-cluster fish bone optical model with hard core correlations is derived from the corresponding resonating group model. The nuclear saturation effect is represented by three different features of inter-cluster interactions:i) by the non-local exchange potential,ii) by a reduced attraction in the region of overlapping clusters,iii) by an effective three-cluster potential. Comparability of the microscopic theory with phenomenological models is established by two off-shell transformations which orthogonalize function bases and avoid appearance of artificial three-body forces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01415716
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    The combined influence of the Pauli principle and saturation on the effectiveα andα α interactions (1985)
    Springer
    The European physical journal 322 (1985), S. 49-57 
    Details
    ISSN: 1434-601X
    Keywords: 21.60.Gx ; 25.10.+s
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The recently developed fish bone optical model with saturation has been applied tonα. andαα scattering. Short ranged nucleon-nucleon correlations, which are responsible for nuclear saturation, have an influence both on the local potential part and on the exchange potential. The local potential becomes less attractive in the inner region and steeper in the surface region; it is better represented by a Woods Saxon shape than by a gaussian. A modification of the exchange potential is caused by the effect of short range correlations on the resonating group norm kernel. It is seen that short ranged nucleonnucleon correlations have no dramatic effect on two-cluster optical potentials. The present calculations rather support conventional phenomenological approaches. Together with older results one may conclude that, in multicluster systems, saturation is predominantly carried by three- and multicluster forces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01412017
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    Paper (German National Licenses)
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