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[en] This is a survey of recent progress in the construction of a realistic nucleon-nucleon potential in which the degrees of freedom of mesons and isobars are taken into account as completely and as carefully as possible. Predictions on the three body systems as well as nuclear matter are also reported
[en] More caution is necessary when claiming isobar effects than had hitherto been thought necessary. This has resulted in improved versions for the transition potentials that generate isobar configurations from purely nucleonic configurations, as is described in section 2. In section 3 the thorny problem of crossed-pion processes involving isobars is briefly mentioned. In section 4 some recent applications with isobar configurations are given. (orig./AH)
[de]Bei der Behauptung von Isobaren-Effekten ist mehr Vorsicht geboten als bisher fuer noetig befunden wurde. Dies fuehrte zu den in Abschnitt 2 beschriebenen verbesserten Versionen fuer die Uebergangspotentiale, die aus reinen Nukleonen-Konfigurationen Isobaren-Konfigurationen erzeugen. In Abschnitt 3 wird kurz auf das heikle Problem der Isobare miteinbeziehenden gekreuzte Pion-Prozesse eingegangen. In Abschnitt 4 werden einige neue Anwendungen mit Isobaren-Konfigurationen behandelt. (orig./AH)
[en] The technique of the effective range expansion is commonly used in nucleon-nucleon scattering to encode the properties of the nuclear force in a small set of parameters. However, the applicability of the effective range expansion is limited by the longest-range part of the nuclear potential, i.e. by the one pion exchange, to the domain of momenta below half the pion mass. In the 1960s the formalism of the modified effective range expansion was developed. It was first used to remove the effects of the Coulomb force to study proton-proton scattering. We apply this formulation to the nucleon-nucleon interaction to separate the known long-range interactions from the rest to be able to go beyond the momentum region described above. To show the effectiveness of this technique, we consider a toy model with a two-range potential and study the behaviour of the parameters of the effective and modified effective range expansion in this two-scale problem.
[en] Interactions of various nuclei in the frame of a simple geometrical approach are considered with the purpose to determine the number of nucleons participating in these interactions. It is shown that on average a part of interacting nucleons does not exceed one quarter of the total number of nucleons of both nuclei. (paper)