1,020 research outputs found
Comparison of Transfer-to-Continuum and Eikonal Models of Projectile Fragmentation Reactions
Spectroscopic properties of nuclei are accessible with projectile
fragmentation reactions, but approximations made in the reaction theory can
limit the accuracy of the determinations. We examine here two models that have
rather different approximations for the nucleon wave function, the target
interaction, and the treatment of the finite duration of the reaction. The
nucleon-target interaction is treated differently in the eikonal and the
transfer-to-continuum model, but the differences are more significant for light
targets. We propose a new parameterization with that in mind. We also propose a
new formula to calculate the amplitude that combines the better treatment of
the wave function in the eikonal model with the better treatment of the target
interaction in the transfer-to-continuum model.Comment: 21 pages, latex file including 3 tables. 5 figures. Submitted to
Phys. Rev.
Initial State Dependence of the Breakup of Weakly Bound Carbon Isotopes
The one-neutron nuclear breakup from the Carbon isotopes C and
C, is calculated as an example of application of the theory of transfer
to the continuum reactions in the formulation which includes spin coupling.
The effect of the energy sharing between the parallel and transverse neutron
momentum distributions is taken into account thus resulting in a theory which
is more general than sudden eikonal approaches. Both effects are necessary to
understand properly the breakup from not too weakly bound orbitals.
Breakup which leaves the core into an excited state below particle threshold is
also considered. The core-target interaction is treated in the smooth cut-off
approximation. By comparing to presently available experimental data we show
how to make some hypothesis on the quantum numbers and occupancy of the neutron
initial state. Possible ambiguities in the interpretation of inclusive cross
sections are discussed.Comment: 22 RevTeX pages,3 ps figures. Phys. Rev. C, accepte
Particle-particle random phase approximation applied to Beryllium isotopes
This work is dedicated to the study of even-even 8-14 Be isotopes using the
particle-particle Random Phase Approximation that accounts for two-body
correlations in the core nucleus. A better description of energies and
two-particle amplitudes is obtained in comparison with models assuming a
neutron closed-shell (or subshell) core. A Wood-Saxon potential corrected by a
phenomenological particle-vibration coupling term has been used for the
neutron-core interaction and the D1S Gogny force for the neutron-neutron
interaction. Calculated ground state properties as well as excited state ones
are discussed and compared to experimental data. In particular, results suggest
the same 2s_1/2-1p_1/2 shell inversion in 13Be as in 11Be.Comment: to appear in Phys. Rev.
Reconstruction of turbulent data with deep generative models for semantic inpainting from TURB-Rot database
We study the applicability of tools developed by the computer vision
community for features learning and semantic image inpainting to perform data
reconstruction of fluid turbulence configurations. The aim is twofold. First,
we explore on a quantitative basis, the capability of Convolutional Neural
Networks embedded in a Deep Generative Adversarial Model (Deep-GAN) to generate
missing data in turbulence, a paradigmatic high dimensional chaotic system. In
particular, we investigate their use in reconstructing two-dimensional damaged
snapshots extracted from a large database of numerical configurations of 3d
turbulence in the presence of rotation, a case with multi-scale random features
where both large-scale organised structures and small-scale highly intermittent
and non-Gaussian fluctuations are present. Second, following a reverse
engineering approach, we aim to rank the input flow properties (features) in
terms of their qualitative and quantitative importance to obtain a better set
of reconstructed fields. We present two approaches both based on Context
Encoders. The first one infers the missing data via a minimization of the L2
pixel-wise reconstruction loss, plus a small adversarial penalisation. The
second searches for the closest encoding of the corrupted flow configuration
from a previously trained generator. Finally, we present a comparison with a
different data assimilation tool, based on Nudging, an equation-informed
unbiased protocol, well known in the numerical weather prediction community.
The TURB-Rot database, http://smart-turb.roma2.infn.it, of roughly 300K 2d
turbulent images is released and details on how to download it are given
Lava effusion â A slow fuse for paroxysms at Stromboli volcano?
International audienceThe 2007 effusive eruption of Stromboli followed a similar pattern to the previous 2002â2003 episode. In both cases, magma ascent led to breaching of the uppermost part of the conduit forming an eruptive fissure that discharged lava down the Sciara del Fuoco depression. Both eruptions also displayed a âparoxysmal' explosive event during lava flow output. From daily effusion rate measurements retrieved from helicopter- and satellite-based infrared imaging, we deduce that the cumulative volume of lava erupted before each of the two paroxysms was similar. Based on this finding, we propose a conceptual model to explain why both paroxysms occurred after this âthreshold' cumulative volume of magma was erupted. The gradual decompression of the deep plumbing system induced by magma withdrawal and eruption, drew deeper volatile-rich magma into the conduit, leading to the paroxysms. The proposed model might provide a basis for forecasting paroxysmal explosions during future effusive eruptions of Stromboli
Core excitation in Coulomb breakup reactions
Within the pure Coulomb breakup mechanism, we investigate the one-neutron
removal reaction of the type A(a,b)X with Be and C
projectiles on a heavy target nucleus Pb at the beam energy of 60
MeV/nucleon. Our intention is to examine the prospective of using these
reactions to study the structure of neutron rich nuclei. Integrated partial
cross sections and momentum distributions for the ground as well as excited
bound states of core nuclei are calculated within the finite range distorted
wave Born approximation as well as within the adiabatic model of the Coulomb
breakup. Our results are compared with those obtained in the studies of the
reactions on a light target where the breakup proceeds via the pure nuclear
mechanism. We find that the transitions to excited states of the core are quite
weak in the Coulomb dominated process as compared to the pure nuclear breakup.Comment: Revtex format, five postscript figures included, to appear in Phys.
Rev.
Lava effusion â a slow fuse for paroxysms at Stromboli volcano?
The 2007 effusive eruption of Stromboli followed a similar pattern to the previous 2002-3 episode. In both cases, magma ascent led to breaching of the uppermost part of the conduit forming an eruptive fissure that discharged lava down the Sciara del Fuoco depression. Both eruptions also displayed a âparoxysmalâ explosive event during lava flow output. From daily effusion rate measurements retrieved from helicopter- and satellite-based infrared imaging, we deduce that the cumulative volume of lava erupted before each of the two paroxysms was similar. Based on this finding, we propose a conceptual model to explain why both paroxysms occurred after this âthresholdâ cumulative volume of magma was erupted. The gradual decompression of the deep plumbing system induced by magma withdrawal and eruption, drew deeper volatile-rich magma into the conduit, leading to the paroxysms. The proposed model might provide a basis for forecasting paroxysmal explosions during future effusive eruptions of Stromboli
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