640 research outputs found
Effective interactions for the nuclear shell model
Various perturbative and non-perturbative many-body techniques are discussed
in this work. Especially, we will focus on the summation of so-called Parquet
diagrams with emphasis on applications to finite nuclei. Here, the subset of
two-body Parquet equations will be discussed. A practical implementation of the
corresponding equations for studies of effective interactions for finite nuclei
is outlined.Comment: 55 pages, latex, to appear in Advances in many-body theory, vol
Gamow shell-model calculations of drip-line oxygen isotopes
We employ the Gamow shell model (GSM) to describe low-lying states of the
oxygen isotopes 24O and 25O. The many-body Schrodinger equation is solved
starting from a two-body Hamiltonian defined by a renormalized low-momentum
nucleon-nucleon (NN) interaction, and a spherical Berggren basis. The Berggren
basis treats bound, resonant, and continuum states on an equal footing, and is
therefore an appropriate representation of loosely bound and unbound nuclear
states near threshold. We show that such a basis is necessary in order to
obtain a detailed and correct description of the low-lying 1+ and 2+ excited
states in 24O. On the other hand, we find that a correct description of binding
energy systematics of the ground states is driven by proper treatment and
inclusion of many-body correlation effects. This is supported by the fact that
we get 25O unstable with respect to 24O in both oscillator and Berggren
representations starting from a 22O core. Furthermore, we show that the
structure of these loosely bound or unbound isotopes are strongly influenced by
the 1S0 component of the NN interaction. This has important consequences for
our understanding of nuclear stability.Comment: 5 pages, 3 figure
Phase Transitions in Neutron Stars and Maximum Masses
Using the most recent realistic effective interactions for nuclear matter
with a smooth extrapolation to high densities including causality, we constrain
the equation of state and calculate maximum masses of rotating neutron stars.
First and second order phase transitions to, e.g., quark matter at high
densities are included. If neutron star masses of from
quasi-periodic oscillations in low mass X-ray binaries are confirmed, a soft
equation of state as well as strong phase transitions can be excluded in
neutron star cores.Comment: Replaced with revised version, 7 pages, 3 figs. To appear in Ap. J.
Let
Closed-shell properties of O with {\em ab initio} coupled-cluster theory
We present an \emph{ab initio} calculation of spectroscopic factors for
neutron and proton removal from O using the coupled-cluster method and a
state-of-the-art chiral nucleon-nucleon interaction at
next-to-next-to-next-to-leading order. In order to account for the coupling to
the scattering continuum we use a Berggren single-particle basis that treats
bound, resonant, and continuum states on an equal footing. We report neutron
removal spectroscopic factors for the O states ,
, and , and proton removal spectroscopic factors for the
N states and . Our calculations support the accumulated
experimental evidence that O is a closed-shell nucleus.Comment: 5 pages, 2 figures, 1 tabl
Effective interactions in medium heavy nuclei
We present a brief overview of microscopic nuclear structure approaches to
nuclei with mass number from 100 to 132. The emphasis is on the shell model and
theories for deriving effective interactions starting from the free
interactions between nucleons. New results for (105,106,107)Sb are presented.Comment: Proceedings of RNB5, 3-8 April 2000, Divonne, France. 6 pages,
Elsevier latex style. To appear in Nucl. Phys.
Generalized contour deformation method in momentum space: two-body spectral structures and scattering amplitudes
A generalized contour deformation method (GCDM) which combines complex
rotation and translation in momentum space, is discussed. GCDM gives accurate
results for bound, virtual (antibound), resonant and scattering states starting
with a realistic nucleon-nucleon interaction. It provides a basis for full
off-shell -matrix calculations both for real and complex input energies.
Results for both spectral structures and scattering amplitudes compare
perfectly well with exact values for the separable Yamaguchi potential.
Accurate calculation of virtual states in the Malfliet-Tjon and the realistic
CD-Bonn nucleon-nucleon interactions are presented.
GCDM is also a promising method for the computation of in-medium properties
such as the resummation of particle-particle and particle-hole diagrams in
infinite nuclear matter. Implications for in-medium scattering are discussed.Comment: 15 pages, revte
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