2,559 research outputs found
Nuclear Structure and Response based on Correlated Realistic NN Interactions
Starting from the Argonne V18 nucleon-nucleon (NN) interaction and using the
Unitary Correlation Operator Method, a correlated interaction v_UCOM has been
constructed, which is suitable for calculations within restricted Hilbert
spaces. In this work we employ the v_UCOM in Hartree-Fock, perturbation-theory
and RPA calculations and we study the ground-state properties of various
closed-shell nuclei, as well as some excited states. The present calculations
provide also important feedback for the optimization of the v_UCOM and valuable
information on its properties. The above scheme offers the prospect of ab
initio calculations in nuclei, regardless of their mass number. It can be used
in conjunction with other realistic NN interactions as well, and with various
many-body methods (Second RPA, QRPA, Shell Model, etc.).Comment: 3 pages, incl. 2 figures; Proc. Int. Conf. on Frontiers in Nuclear
Structure, Astrophysics and Reactions (FINUSTAR), Kos, Greece, Sept.200
Large-scale calculations of supernova neutrino-induced reactions in Z=8-82 target nuclei
Background: In the environment of high neutrino-fluxes provided in
core-collapse supernovae or neutron star mergers, neutrino-induced reactions
with nuclei contribute to the nucleosynthesis processes. A number of
terrestrial neutrino detectors are based on inelastic neutrino-nucleus
scattering and modeling of the respective cross sections allow predictions of
the expected detector reaction rates.
Purpose: To provide a self-consistent microscopic description of
neutrino-nucleus cross sections involving a large pool of Z = 8 - 82 nuclei for
the implementation in models of nucleosynthesis and neutrino detector
simulations.
Methods: Self-consistent theory framework based on relativistic nuclear
energy density functional is employed to determine the nuclear structure of the
initial state and relevant transitions to excited states induced by neutrinos.
The weak neutrino-nucleus interaction is employed in the current-current form
and a complete set of transition operators is taken into account.
Results: We perform large-scale calculations of charged-current
neutrino-nucleus cross sections, including those averaged over supernova
neutrino fluxes, for the set of even-even target nuclei from oxygen toward lead
(Z = 8 - 82), spanning N = 8 - 182 (OPb pool). The model calculations include
allowed and forbidden transitions up to J = 5 multipoles.
Conclusions: The present analysis shows that the self-consistent calculations
result in considerable differences in comparison to previously reported cross
sections, and for a large number of target nuclei the cross sections are
enhanced. Revision in modeling r-process nucleosynthesis based on a
self-consistent description of neutrino-induced reactions would allow an
updated insight into the origin of elements in the Universe and it would
provide the estimate of uncertainties in the calculated element abundance
patterns.Comment: 25 pages, 12 figures, submitted to Physical Review
Nuclear Structure in the UCOM Framework: From Realistic Interactions to Collective Excitations
The Unitary Correlation Operator Method (UCOM) provides a means for nuclear
structure calculations starting from realistic NN potentials. The dominant
short-range central and tensor correlations are described explicitly by a
unitary transformation. The application of UCOM in the context of the no-core
shell model provides insight into the interplay between dominant short-range
and residual long-range correlations in the nuclear many-body problem. The use
of the correlated interaction within Hartree-Fock, many-body perturbation
theory, and Random Phase Approximation gives access to various nuclear
structure observables throughout the nuclear chart.Comment: 9 pages, 3 figures, invited talk at the 2nd Int. Conf. on "Collective
Motion in Nuclei under Extreme Conditions" (COMEX 2), Sankt Goar, German
Neutral-current neutrino-nucleus cross sections based on relativistic nuclear energy density functional
Background: Inelastic neutrino-nucleus scattering through the weak
neutral-current plays important role in stellar environment where transport of
neutrinos determine the rate of cooling. Since there are no direct experimental
data on neutral-current neutrino-nucleus cross sections available, only the
modeling of these reactions provides the relevant input for supernova
simulations. Purpose: To establish fully self-consistent framework for
neutral-current neutrino-nucleus reactions based on relativistic nuclear energy
density functional. Methods: Neutrino-nucleus cross sections are calculated
using weak Hamiltonian and nuclear properties of initial and excited states are
obtained with relativistic Hartree-Bogoliubov model and relativistic
quasiparticle random phase approximation that is extended to include pion
contributions for unnatural parity transitions. Results: Inelastic
neutral-current neutrino-nucleus cross sections for 12C, 16O, 56Fe, 56Ni, and
even isotopes {92-100}Mo as well as respective cross sections averaged over
distribution of supernova neutrinos. Conclusions: The present study provides
insight into neutrino-nucleus scattering cross sections in the neutral channel,
their theoretical uncertainty in view of recently developed microscopic models,
and paves the way for systematic self-consistent large-scale calculations
involving open-shell target nuclei.Comment: 25 pages, 9 figures, 2 tables, submitted to Physical Review
Structure of the doublet bands in doubly odd nuclei: The case of
The structure of the doublet bands in is
investigated within the framework of the Interacting Vector Boson Fermion Model
(IVBFM). A new, purely collective interpretation of these bands is given on the
basis of the used boson-fermion dynamical symmetry of the model. The energy
levels of the doublet bands as well as the absolute and
transition probabilities between the states of both yrast and yrare bands are
described quite well. The observed odd-even staggering of both and
values is reproduced by the introduction of an appropriate interaction
term of quadrupole type, which produces such a staggering effect in the
transition strengths. The calculations show that the appearance of doublet
bands in certain odd-odd nuclei could be a consequence of the realization of a
larger dynamical symmetry based on the non-compact supersymmetry group
.Comment: 12 pages, 8 figure
Pygmy dipole resonance in exotic nuclei
The evolution of the PDR strength with the neutron excess is investigated in
Sn isotopic and N=82 isotonic chains with regard to its possible connection
with the neutron skin thickness. For this purpose a recently proposed method
incorporating both HFB and multi-phonon QPM theory is applied. Analysis of the
corresponding neutron and proton dipole transition densities is presented.Comment: International Workshop on Nuclear Physics 28th Course - Radioactive
Beams, Nuclear Dynamics and Astrophysics, Ettore Majorana Center for
Scientific Cultur
Collective excitations in the Unitary Correlation Operator Method and relativistic QRPA studies of exotic nuclei
The collective excitation phenomena in atomic nuclei are studied in two
different formulations of the Random Phase Approximation (RPA): (i) RPA based
on correlated realistic nucleon-nucleon interactions constructed within the
Unitary Correlation Operator Method (UCOM), and (ii) relativistic RPA (RRPA)
derived from effective Lagrangians with density-dependent meson-exchange
interactions. The former includes the dominant interaction-induced short-range
central and tensor correlations by means of an unitary transformation. It is
shown that UCOM-RPA correlations induced by collective nuclear vibrations
recover a part of the residual long-range correlations that are not explicitly
included in the UCOM Hartree-Fock ground state. Both RPA models are employed in
studies of the isoscalar monopole resonance (ISGMR) in closed-shell nuclei
across the nuclide chart, with an emphasis on the sensitivity of its properties
on the constraints for the range of the UCOM correlation functions. Within the
Relativistic Quasiparticle RPA (RQRPA) based on Relativistic Hartree-Bogoliubov
model, the occurrence of pronounced low-lying dipole excitations is predicted
in nuclei towards the proton drip-line. From the analysis of the transition
densities and the structure of the RQRPA amplitudes, it is shown that these
states correspond to the proton pygmy dipole resonance.Comment: 15 pages, 4 figures, submitted to Physics of Atomic Nuclei,
conference proceedings, "Frontiers in the Physics of Nucleus", St.
Petersburg, 28. June-1. July, 200
Hartree-Fock and Many-Body Perturbation Theory with Correlated Realistic NN-Interactions
We employ correlated realistic nucleon-nucleon interactions for the
description of nuclear ground states throughout the nuclear chart within the
Hartree-Fock approximation. The crucial short-range central and tensor
correlations, which are induced by the realistic interaction and cannot be
described by the Hartree-Fock many-body state itself, are included explicitly
by a state-independent unitary transformation in the framework of the unitary
correlation operator method (UCOM). Using the correlated realistic interaction
V_UCOM resulting from the Argonne V18 potential, bound nuclei are obtained
already on the Hartree-Fock level. However, the binding energies are smaller
than the experimental values because long-range correlations have not been
accounted for. Their inclusion by means of many-body perturbation theory leads
to a remarkable agreement with experimental binding energies over the whole
mass range from He-4 to Pb-208, even far off the valley of stability. The
observed perturbative character of the residual long-range correlations and the
apparently small net effect of three-body forces provides promising
perspectives for a unified nuclear structure description.Comment: 14 pages, 8 figures, 3 tables, using REVTEX
Bursts in the Chaotic Trajectory Lifetimes Preceding the Controlled Periodic Motion
The average lifetime () it takes for a randomly started trajectory
to land in a small region () on a chaotic attractor is studied. is
an important issue for controlling chaos. We point out that if the region
is visited by a short periodic orbit, the lifetime strongly deviates
from the inverse of the naturally invariant measure contained within that
region (). We introduce the formula that relates
to the expanding eigenvalue of the short periodic orbit
visiting .Comment: Accepted for publication in Phys. Rev. E, 3 PS figure
Lead-antimony sulfosalts from Tuscany (Italy). XXIII. Andreadiniite, CuAg7HgPb7Sb24S48, a new oversubstituted (Cu,Hg)-rich member of the andorite homeotypic series from the Monte Arsiccio mine, Apuan Alps
The new mineral species andreadiniite, CuAg7HgPb7Sb24S48, was discovered in a quartz vein embedded in metadolostone from the Sant'Olga tunnel, Monte Arsiccio mine, Stazzema, Apuan Alps, Tuscany, Italy. It occurs as black anhedral grains, up to some mm in size, with a metallic luster, associated with sphalerite and stibnite. Under the ore microscope, andreadiniite is white, with a slightly yellow-bronze tint. Pleochroism was not observed. Anisotropism is weak, in shades of gray to bluish-gray. Reflectance percentages for the four COM wavelengths are [R-min, R-max (%), (lambda)]: 34.8, 36.4 (470 nm); 33.5, 35.1 (546 nm); 32.9, 35.0 (589 nm); and 31.8, 32.4 (650 nm). Electron-microprobe analysis gave (in wt% - average of seven spot analyses): Cu 1.06(2), Ag 11.25(18), Tl 0.45(9), Hg 2.76 (14), Pb 19.95(16), As 1.55(5), Sb 40.45(21), S 22.23(11), total 99.70(42). On the basis of Sigma Me= 40 atoms per formula unit, the chemical formula is Cu1.14Ag7.12Tl0.15Hg0.94Pb6.57(Sb22.68As1.41) S24.09S47.33, ideally CuAg7HgPb7Sb24S48. The main diffraction lines, corresponding to multiple hkl indices, are [d in angstrom (relative visual intensity)]: 3.719 (ms), 3.406 (s), 3.277 (s), 2.885 (s), 2.740 (ms), 2.131 (ms), 2.055 (s), and 1.788(s). The crystal structure study gave a monoclinic pseudo-orthorhombic unit cell, space group P2(1)/c, with a = 19.0982(14), b = 17.0093(11), c = 13.0008(10) angstrom, beta = 90.083(4)degrees, V = 4223.3(5) angstrom(3), Z = 2. The crystal structure was solved and refined to R-1 = 0.067 on the basis of 9756 reflections with F-o> 4 sigma(F-o) and 424 refined parameters. Andreadiniite is a new L-4,L-4 homologue belonging to the andorite sub-series of Sb-rich members within the lillianite homologous series. Antimony substituting Pb gives an ideal substitution percentage n = 106.25%. Distribution of minor cations (Hg, Cu, As) is detailed. Mercury may play a critical role for the stabilization of andreadiniite, through a complex substitution rule implying three cation sites: Pb2++Sb3++Ag+ -> Sb3++Ag++Hg2+. Copper is subordinate to the twoHg-rich sites. The name honors Andrea Dini (b. 1966) for his contribution to the knowledge of ore deposits from Tuscany and, in particular, the ore geology and mineralogy of Hg ores from Apuan Alps
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