A. Polls

Two-body correlations in nuclear systems

Abstract Correlations in the nuclear wave-function beyond the mean-field or Hartree-Fock approximation are very important to describe basic properties of nuclear structure. Various approaches to account for such correlations are described and compared to each other. This includes the holeline expansion, the coupled cluster or “exponential S” approach, the self-consistent evaluation of Greens functions, variational approaches using correlated basis functions and recent developments employing quantum Monte-Carlo techniques. Details of these correlations are explored and their sensitivity to the underlying nucleon-nucleon interaction. Special attention is paid to the attempts to investigate these correlations in exclusive nucleon knock-out experiments induced by electron scattering. Another important issue of nuclear structure physics is the role of relativistic effects as contained in phenomenological mean field models. The sensitivity of various nuclear structure observables on these relativistic features are investigated. The report includes the discussion of nuclear matter as well as finite nuclei.

Single-particle properties and short-range correlations in nuclear matter

Abstract Ladder correlations are studied with inclusion of hole-hole propagation to all orders. The resulting effective interaction is separated into a forward-going and a backward-going contribution with the numerical use of dispersion relations. This procedure allows the correct calculation of the corresponding self-energy terms. Self-consistency between the ladders and the self-energy is established for the quasi-particle energy. Calculations are performed with semi-realistic interactions derived from Reids soft-core interaction to avoid the appearance of pairing instabilities. A careful study of the complete momentum and energy dependence of the resulting self-energy is made for various densities. Effective mass contributions are studied coming from both the k - and ω-dependence of the self-energy. Accurate calculation of all relevant spectral functions is performed with proper fulfillment of the sum rule and quasi-particle properties are discussed. An important fraction of the single-particle strength is found at very high energy due to the realistic short-range repulsion in the interaction. From the hole spectral function the momentum distribution is calculated at various densities. The depletion due to the influence of short-range correlations around normal nuclear matter density amounts to about 13%.

Hyperon-hyperon interactions and properties of neutron star matter

We present results from Brueckner-Hartree-Fock calculations for

Estimation of the effect of hyperonic three-body forces on the maximum mass of neutron stars

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Effective mass of one 4He atom in liquid 3He.

-stable neutron star matter with nucleonic and hyperonic degrees of freedom, employing the most recent parametrizations of the baryon-baryon interaction of the Nijmegen group. It is found that the only strange baryons emerging in

Modern nucleon-nucleon potentials and symmetry energy in infinite matter

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Effective mass of one He 4 atom in liquid He 3

-stable matter up to total baryonic densities of 1.2

Antikaon nuclear potential in hot and dense matter

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Correlations in hot asymmetric nuclear matter

are

Strange nuclear matter within Brueckner-Hartree-Fock theory

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