3,129 research outputs found
Charge and matter distributions and form factors of light, medium and heavy neutron-rich nuclei
Results of charge form factors calculations for several unstable neutron-rich
isotopes of light, medium and heavy nuclei (He, Li, Ni, Kr, Sn) are presented
and compared to those of stable isotopes in the same isotopic chain. For the
lighter isotopes (He and Li) the proton and neutron densities are obtained
within a microscopic large-scale shell-model, while for heavier ones Ni, Kr and
Sn the densities are calculated in deformed self-consistent mean-field Skyrme
HF+BCS method. We also compare proton densities to matter densities together
with their rms radii and diffuseness parameter values. Whenever possible
comparison of form factors, densities and rms radii with available experimental
data is also performed. Calculations of form factors are carried out both in
plane wave Born approximation (PWBA) and in distorted wave Born approximation
(DWBA). These form factors are suggested as predictions for the future
experiments on the electron-radioactive beam colliders where the effect of the
neutron halo or skin on the proton distributions in exotic nuclei is planned to
be studied and thereby the various theoretical models of exotic nuclei will be
tested.Comment: 26 pages, 11 figures, 3 tables, accepted for publication in Phys.
Rev.
Relativistic current densities for bound spin-orbit partners and the longitudinal-transverse response in (e,ép) processes
Scalar, baryon and vector-current densities in coordinate and momentum space are calculated within a relativistic mean-field model. The role of the low components of the bound nucleon wave function is investigated in detail for different spin-orbit partner shells. We show that the relative importance of the negative-energy projection components can be explained from the different quantum numbers involved in the relativistic wave function. This fact has proved to be important in the analysis of various electron scattering observables even for low-medium values of the bound nucleon momentum.DGICYT PB/95–0123 PB/95–0533–
New ground-based observational methods and instrumentation for asteroseismology
Space instrumentation like SOHO, MOST, CoRoT and Kepler has been and is being
built to attain very high precision data to be used for asteroseismic analysis.
Nonetheless, there is a very strong need for providing additional information,
especially on mode identification. With this contribution I will review the
efforts been put on new ground-based instrumentation and the methodology that
can be used to achieve this aim.Comment: 6 pages. Review contribution to be published in Astrophysics and
Space Science Proceedings series (ASSP), in the proceedings of "20th Stellar
Pulsation Conference Series: Impact of new instrumentation and new insights
in stellar pulsations", 5-9 September 2011, Granada, Spai
Scaling Function, Spectral Function and Nucleon Momentum Distribution in Nuclei
The link between the scaling function extracted from the analysis of (e,e')
cross sections and the spectral function/momentum distribution in nuclei is
revisited. Several descriptions of the spectral function based on the
independent particle model are employed, together with the inclusion of nucleon
correlations, and effects of the energy dependence arising from the width of
the hole states are investigated. Although some of these approaches provide
rough overall agreement with data, they are not found to be capable of
reproducing one of the distinctive features of the experimental scaling
function, namely its asymmetry. However, the addition of final-state
interactions, incorporated in the present study using either relativistic mean
field theory or via a complex optical potential, does lead to asymmetric
scaling functions in accordance with data. The present analysis seems to
indicate that final-state interactions constitute an essential ingredient and
are required to provide a proper description of the experimental scaling
function.Comment: 29 pages, 13 figures, accepted for publication in Physical Review
Analysis of polarized 16O(e→,e′p→) observables within the relativistic distorted wave impulse approximation
15 págs.; 9 figs. ; PACS number(s): 25.30.Rw, 14.20.Gk, 24.10.Jv, 24.30.GdRecoil nucleon transferred polarization observables in coincidence quasielastic electron scattering are studied within the relativistic distorted wave impulse approximation. Results for response functions and polarization asymmetries are discussed for proton knockout from p1/2, p 3/2, and s1/2 shells in 16O. The impact of spinor distortion is examined by comparing the fully relativistic calculation with results obtained by projecting out the negative-energy components. In particular, a careful analysis of effects linked to the description of the bound and scattered relativistic nucleon wave functions is presented. The high sensitivity of some polarization observables to the dynamical enhancement of the lower components, already shown within the relativistic plane wave impulse approximation, is proven to be maintained in the relativistic distorted wave approach. Semi-relativistic approaches based on the effective momentum approximation are also studied. Finally, comparison with experimental data and a brief analysis of effects linked to medium modified form factors is presented. ©2004 American Physical SocietyThis work was partially supported by funds provided by
DGI (Spain) and FEDER funds, under Contract Nos.
BFM2002-03315, BFM2002-03562, FPA2002-04181-C04-
04, and BFM2000-0600 and by the Junta de Andalucía
(Spain) and in part by the U.S. Department of Energy under
Cooperative Research Agreement No. DE-FC02-
94ER40818. M.C.M. and J.R.V. acknowledge financial support
from the Fundación Cámara (University of Sevilla) and
the Consejería de Educación de la Comunidad de Madrid,
respectivelyPeer Reviewe
Symplectic evolution of Wigner functions in markovian open systems
The Wigner function is known to evolve classically under the exclusive action
of a quadratic hamiltonian. If the system does interact with the environment
through Lindblad operators that are linear functions of position and momentum,
we show that the general evolution is the convolution of the classically
evolving Wigner function with a phase space gaussian that broadens in time. We
analyze the three generic cases of elliptic, hyperbolic and parabolic
Hamiltonians. The Wigner function always becomes positive in a definite time,
which is shortest in the hyperbolic case. We also derive an exact formula for
the evolving linear entropy as the average of a narrowing gaussian taken over a
probability distribution that depends only on the initial state. This leads to
a long time asymptotic formula for the growth of linear entropy.Comment: this new version treats the dissipative cas
Effects of T=0 two body matrix elements on M1 and Gamow-Teller transitions: isospin decomposition
We perform calculations for M1 transitions and allowed Gamow Teller (GT)
transitions in the even-even Titanium isotopes - Ti, Ti, and
Ti. We first do calculations with the FPD6 interaction. Then to study
the effect of T=0 matrix elements on the M1 and GT rates we introduce a second
interaction in which all the T=0 matrix elements are set equal to zero and a
third in which all the T=0 matrix elements are set to a constant. For the
latter two interactions the T=1 matrix elements are the same as for FPD6. We
are thus able to study the effects of the fluctuating T=0 matrix elements on M1
and GT rates
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