E. Mavrommatis

Nuclear mass systematics using neural networks

Abstract New global statistical models of nuclidic (atomic) masses based on multilayered feedforward networks are developed. One goal of such studies is to determine how well the existing data, and only the data, determines the mapping from the proton and neutron numbers to the mass of the nuclear ground state. Another is to provide reliable predictive models that can be used to forecast mass values away from the valley of stability. Our study focuses mainly on the former goal and achieves substantial improvement over previous neural-network models of the mass table by using improved schemes for coding and training. The results suggest that with further development this approach may provide a valuable complement to conventional global models.

Nuclear vorticity and the low-energy nuclear response : towards the neutron drip line

Abstract The transition density and current provide valuable insight into the nature of nuclear vibrations. Nuclear vorticity is a quantity related to the transverse transition current. In this work, we study the evolution of the strength distribution, related to density fluctuations, and the vorticity strength distribution, as the neutron drip line is approached. Our results on the isoscalar, natural-parity multipole response of Ni isotopes, obtained by using a self-consistent Skyrme–Hartree–Fock + Continuum RPA model, indicate that, close to the drip line, the low-energy response is dominated by L > 1 vortical transitions.

The Two-body momentum distribution in finite nuclei

The two-body momentum distribution η2(p→1,p→2) of nuclei is studied. First, a compact analytical expression is derived for Z=N, l-closed nuclei, within the context of the independent particle shell model. Application to the light closed-shell nucleus 16O is included and discussed. Next, the effect of dynamical, short-range correlations is investigated in the case of the light nucleus 4He, by including Jastrow-type correlations in the formalism. The effect is significant for large values of p1 and p2 and for angles between the vectors p→1 and p→2 close to γ=180°and 0°.The two-body momentum distribution n2(p1,p2) of nuclei is studied. First, a compact analytical expression is derived for Z=N l-closed nuclei, within the context of the independent-particle shell model. Application to the light closed-shell nucleus 16O is included and discussed. Next, the effect of dynamical, short-range correlations is investigated in the case of 4He, by including Jastrow-type correlations in the formalism. The effect is significant for large values of p1 and p2 and for angles between the vectors p1 and p2 close to 180 deg. and 0.

The one-body and two-body density matrices of finite nuclei with an appropriate treatment of the center-of-mass motion⋆

Abstract.The one-body and two-body density matrices in coordinate space and their Fourier transforms in momentum space are studied for a nucleus (a nonrelativistic, self-bound finite system). Unlike the usual procedure, suitable for infinite or externally bound systems, they are determined as expectation values of appropriate intrinsic operators, dependent on the relative coordinates and momenta (Jacobi variables) and acting on intrinsic wave functions of nuclear states. Thus, translational invariance (TI) is respected. When handling such intrinsic quantities, we use an algebraic technique based upon the Cartesian representation, in which the coordinate and momentum operators are linear combinations of the creation and annihilation operators

Generalized momentum distribution in finite nuclei

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The effect of short-range correlations on the generalized momentum distribution in finite nuclei

and

A microscopic investigation of the transition form factor in the region of collective multipole excitations of stable and unstable nuclei

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STATISTICAL MODELING OF NUCLEAR SYSTEMATICS

for oscillator quanta. Each of the relevant multiplicative operators can then be reduced to the form: one exponential of the set {

The One‐Body and Two‐Body Density Matrices of Finite Nuclei and Center‐of‐Mass Correlations

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Nuclear Mass Systematics With Neural Nets And Astrophysical Nucleosynthesis

} times another exponential of the set {