455 research outputs found
Gamow-Teller response and its spreading mechanism in doubly magic nuclei
The scope of the paper is to apply a state-of-the-art beyond mean-field model
to the description of the Gamow-Teller response in atomic nuclei. This topic
recently attracted considerable renewed interest, due, in particular, to the
possibility of performing experiments in unstable nuclei. We study the cases of
Ca, Ni, Sn and Pb. Our model is based on a fully
self-consistent Skyrme Hartree-Fock plus random phase approximation. The same
Skyrme interaction is used to calculate the coupling between particles and
vibrations, which leads to the mixing of the Gamow-Teller resonance with a set
of doorway states and to its fragmentation. We compare our results with
available experimental data. The microscopic coupling mechanism is also
discussed in some detail.Comment: 27 pages, 10 figure
Jean-Baptiste Say et la révolution industrielle… ou les certitudes d'un entrepreneur du secteur textile
International audienceFrom three texts by Jean-Baptiste Say (Olbie ... 1800, Full Course…1819 and a Letter to Malthus in 1820 processing machinery) and a historical approach to technical changes of this period, we will make three observations : 1. Say-entrepreneur is at the heart of the industrial revolution but can not have an overall vision... ; 2. His multiform social status can't develop this overall vision and leads to an descriptive vision favoring the recensions... ; 3. Despite this absence, Say was one of the first economists to focus on the technical changes despite a conflict between his approach in terms of production and his conclusions focused on the creation of utilities and income distribution and expenses. In conclusion, we shall identify a second "Law of Say": the increasing difficulty of financing innovations and of their developments lead to the cancellation of their disadvantages.À partir de trois textes de Jean-Baptiste Say (Olbie… de 1800, Cours complet… de 1819 et une Lettre à Malthus en 1820 traitant des machines) et d'une approche historique des changements techniques de cette période, nous formulerons trois constats : 1. Say-entrepreneur est au coeur de la révolution industrielle mais ne peut en avoir une vision d'ensemble… ; 2. Son statut social multiforme l'empêche de développer cette vision d'ensemble et le conduit à une vision descriptive privilégiant les recensions… ; 3. Malgré cette absence, Say a été l'un des premiers économistes à s'intéresser aux changements techniques même si une contradiction apparaît entre son approche en terme de production et ses conclusions centrées sur la création d'utilités et sur la répartition des revenus et des charges. En conclusion, on identifiera ainsi une seconde "Loi de Say" : les difficultés croissantes du financement des innovations et leur développement conduisent à l'annulation de leurs inconvénients
Characterization of vorticity in pygmy resonances and soft-dipole modes with two-nucleon transfer reactions
The properties of the two-quasiparticle-like soft E1-modes and PDR have been
and are systematically studied with the help of inelastic and electromagnetic
experiments which essentially probe the particle-hole components of these
vibrations. It is shown that further insight in their characterisation can be
achieved with the help of two-nucleon transferreactions, in particular
concerning the particle-particle components of the modes, in terms of absolute
differential cross sections which take properly into account successive and
simultaneous transfer mechanisms corrected for non-orthogonality, able to
reproduce the experimental findings at the 10% level. The process
LiLi(1) is discussed, and absolute cross sections
predicted.Comment: Typo corrected with respect to previous versio
Radioactive beams and inverse kinematics: probing the quantal texture of the nuclear vacuum
The properties of the quantum electrodynamic (QED) vacuum in general, and of
the nuclear vacuum (ground) state in particular are determined by virtual
processes implying the excitation of a photon and of an electron--positron pair
in the first case and of, for example, the excitation of a collective
quadrupole surface vibration and a particle--hole pair in the nuclear case.
Signals of these processes can be detected in the laboratory in terms of what
can be considered a nuclear analogue of Hawking radiation. An analogy which
extends to other physical processes involving QED vacuum fluctuations like the
Lamb shift, pair creation by rays, van der Waals forces and the
Casimir effect, to the extent that one concentrates on the eventual outcome
resulting by forcing a virtual process to become real, and not on the role of
the black hole role in defining the event horizon. In the nuclear case, the
role of this event is taken over at a microscopic, fully quantum mechanical
level, by nuclear probes (reactions) acting on a virtual particle of the zero
point fluctuation (ZPF) of the nuclear vacuum in a similar irreversible,
no--return, fashion as the event horizon does, letting the other particle,
entangled with the first one, escape to infinity, and eventually be detected.
With this proviso in mind one can posit that the reactions
H(Be,Be;3.37 ))H and
H(Li,Li(; 2.69 ))H together with the
associated decay processes indicate a possible nuclear analogy of
Hawking radiation
One- and two- neutron halo at the dripline. From 11Be to 11Li and back: 10Li and parity inversion
The nuclei 11Be and 11Li provide paradigmatic examples of one-and two-
neutron halo systems. Because the reaction 1H(11Li,9Li)3H is dominated by
successive transfer, one can use the quantitative picture emerging from a nu-
clear field theory description of the structure and reaction mechanism of the
above Cooper pair transfer process and of the 2H(10Be,11Be)1H and
1H(11Be,10Be)2H reactions, to shed light on the structure of 10Li. This
analysis provides important support for a parity inverted scenario with a 1/2+
virtual state at about 0.2 MeV.Comment: Proceedings of the 15th Varenna Conference on Nuclear Reaction
Mechanism
Structure and reactions of 11Be: many-body basis for single-neutron halo
The exotic nucleus 11Be has been extensively studied and much experimental
information is available on the structure of this system. Treating, within the
framework of empirically renormalised nuclear field theory in both
configuration and 3D-space, the mixing of bound and continuum single-particle
states through the coupling to collective particle-hole (p,h) and pairing
vibrations of the 10Be core, as well as Pauli principle acting not only between
the particles explicitly considered and those participating in the collective
states, but also between fermions involved in two-phonon virtual states it is
possible, for the first time, to simultaneously and quantitatively account for
the energies of the 1/2+,1/2- low-lying states, the centroid and line shape of
the 5/2+ resonance, the one-nucleon stripping and pickup absolute differential
cross sections involving 11Be as either target or residual nucleus, and the
dipole transitions connecting the 1/2+ and 1/2- parity inverted levels as well
as the charge radius, thus providing a unified and exhaustive characterisation
of the many-body effects which are at the basis of this paradigmatic
one-neutron halo system.Comment: Supplemental materials include
The 9Li(d,p) reaction, a specific probe of 10Li, paradigm of parity--inverted nuclei around N=6 closed shell
We show, within the framework of renormalized nuclear field theory and of the
induced reaction surrogate formalism, that the highly debated Li
structure, observed in a recent Li(d,p)Li one--neutron transfer
experiment is consistent with or better, requires the presence of a virtual
state of similar single--particle strength than that of the
resonance at 0.45 0.03 MeV. Based on continuum spectroscopy self-energy
techniques, we find that the physical mechanism responsible for parity
inversion in Li is the same as that at the basis of the similar
phenomenon observed in Be and to that needed in Li to have an
important --wave ground state component. Furthermore, it is also consistent
with the (normal) sequence of the and levels in the
isotones B and C.Comment: Revised text and figures. The paper includes supplemental materia
Inversion Formulas for the Dunkl Intertwining Operator and Its Dual on Spaces of Functions and Distributions
In this paper we prove inversion formulas for the Dunkl intertwining operator
and for its dual and we deduce the expression of the
representing distributions of the inverse operators and
, and we give some applications.Comment: This is a contribution to the Special Issue on Dunkl Operators and
Related Topics, published in SIGMA (Symmetry, Integrability and Geometry:
Methods and Applications) at http://www.emis.de/journals/SIGMA
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