535 research outputs found
Medium polarization isotopic effects on nuclear binding energies
There exist several effective interactions whose parameters are fitted to
force mean field predictions to reproduce experimental findings of finite
nuclei and calculated properties of infinite nuclear matter. Exploiting this
tecnique one can give a good description of nuclear binding energies. We
present evidence that further progress can be made by taking into account
medium polarization effects associated with surface and pairing vibrations.Comment: 7 pages, 5 figure
Neutrino Capture Cross Sections for Ar-40 and beta-decay of Ti-40
Shell-model calculations of solar neutrino absorption cross sections for
Ar, the proposed component of the ICARUS detector, are presented. It is
found that low-lying Gamow-Teller transitions lead to a significant enhancement
of the absorption rate over that expected from the Fermi transition between the
isobaric analog states, leading to an overall absorption rate of 6.7 SNU. We
also note that the pertinent Gamow-Teller transitions in ^{\sss 40}Ar are
experimentally accessible from the -decay of the mirror nucleus ^{\sss
40}Ti. Predictions for the branching ratios to states in ^{\sss 40}Sc are
presented, and the theoretical halflife of 53~ms is found to be in good
agreement with the experimental value of ~ms.Comment: 12 pages including references and table. NTGMI-94-
Rho meson properties in the Nambu-Jona-Lasinio model
Some properties of the rho vector meson are calculated within the
Nambu-Jona-Lasinio model, including processes that go beyond the random phase
approximation. To classify the higher order contributions, we adopt as
expansion parameter. In particular, we evaluate the leading order contributions
to the decay width, obtaining the value MeV, and to the shift of the rho mass which turns out to be lowered by 64
MeV with respect to its RPA value. A set of model parameters is determined
accordingly.Comment: 21 pages Latex, 4 figures, to be published in Z. Phys.
Quantum calculation of vortices in the inner crust of neutron stars
We study, within a quantum mechanical framework based on self-consistent mean
field theory, the interaction between a vortex and a nucleus immersed in a sea
of free neutrons, a scenario representative of the inner crust of neutron
stars. Quantal finite size effects force the vortex core outside the nucleus,
influencing vortex pinning in an important way
Particle transfer reactions with the time-dependent Hartree-Fock theory using a particle number projection technique
A particle-number projection technique is used to calculate transfer
probabilities in the O+Pb reaction below the fusion barrier. The
time evolution of the many-body wave function is obtained with the
time-dependent Hartree-Fock (TDHF) mean-field theory. The agreement with
experimental data for the sum of the proton-transfer channels is good,
considering that TDHF has no parameter adjusted on reaction mechanism. Some
perspectives for extensions beyond TDHF to include cluster-transfers are
discussed.Comment: Ref. 30 update
Challenges in the description of the atomic nucleus: Unification and interdisciplinarity
Nuclear physics, in general, and theoretical nuclear physics, in particular, have provided the physics community at large, among other things, with the paradigm of spontaneous symmetry breaking phenomena in finite many-body systems. The study of the associated mechanisms of symmetry restoration has shed light on the microscopic structure of the corresponding condensates, in particular on the superfluid phase, allowing to study Cooper pair tunnelling into superfluid nuclei (related to the Josephson effect), in terms of individual quantum states and reaching, in doing so, a new milestone: that of unifying structure and reactions, these last processes being found at the basis of the formulation of quantum mechanics (probability interpretation, Born). In the process, nuclear physicists have extended the validity of BCS theory of superconductivity to the single Cooper pair situation, let alone discovering unexpected mechanism to break gauge invariance. The insight obtained from pair transfer research is likely to have important consequences in the study of double charge exchange processes, and thus in the determination of the nuclear matrix element associated with neutrinoless double beta decay, eventually providing an important test of the Standard Model. Time, thus, seems ripe for nuclear theorists to take centre stage, backed by a wealth of experimental information and by their interdisciplinary capacity to connect basic physical concepts across the borders. With the help of these elements they can aim at fully revealing the many facets of their femtometer many-body system, from vacuum zero point fluctuations to new exotic modes of nuclear excitations and of their interweaving, resulting in powerful effective field theories. Unless. Unless they are not able to free themselves from words like ab initio or fundamental, and to adapt a relax attitude concerning Skyrme, tensor, etc., forces, as well as regarding the quest for “the” Hamiltonian
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