1,154 research outputs found
New potentialities of the Liège intranuclear cascade (INCL) model for reactions induced by nucleons and light charged particles
The new version (INCL4.6) of the Li`ege intranuclear cascade (INC) model for
the description of spallation reactions is presented in detail. Compared to the
standard version (INCL4.2), it incorporates several new features, the most
important of which are: (i) the inclusion of cluster production through a
dynamical phase space coalescence model, (ii) the Coulomb deflection for
entering and outgoing charged particles, (iii) the improvement of the treatment
of Pauli blocking and of soft collisions, (iv) the introduction of experimental
threshold values for the emission of particles, (v) the improvement of pion
dynamics, (vi) a detailed procedure for the treatment of light-cluster induced
reactions taking care of the effects of binding energy of the nucleons inside
the incident cluster and of the possible fusion reaction at low energy.
Performances of the new model concerning nucleon-induced reactions are
illustrated. Whenever necessary, the INCL4.6 model is coupled to the ABLA07
deexcitation model and the respective merits of the two models are then
tentatively disentangled. Good agreement is generally obtained in the 200 MeV-2
GeV range. Below 200 MeV and down to a few tens of MeV, the total reaction
cross section is well reproduced and differential cross sections are reasonably
well described. The model is also tested for light-ion induced reactions at low
energy, below 100 MeV incident energy per nucleon. Beyond presenting the update
of the INCL4.2 model, attention has been paid to applications of the new model
to three topics for which some particular aspects are discussed for the first
time: production of clusters heavier than alpha particles, longitudinal residue
recoil velocity and its fluctuations, total reaction cross section and the
residue production cross sections for low energy incident light ions.Comment: 29 pages, 26 figure
Weak in Space, Log in Time Improvement of the Lady{\v{z}}enskaja-Prodi-Serrin Criteria
In this article we present a Lady{\v{z}}enskaja-Prodi-Serrin Criteria for
regularity of solutions for the Navier-Stokes equation in three dimensions
which incorporates weak norms in the space variables and log improvement
in the time variable.Comment: 14 pages, to appea
The "Symplectic Camel Principle" and Semiclassical Mechanics
Gromov's nonsqueezing theorem, aka the property of the symplectic camel,
leads to a very simple semiclassical quantiuzation scheme by imposing that the
only "physically admissible" semiclassical phase space states are those whose
symplectic capacity (in a sense to be precised) is nh + (1/2)h where h is
Planck's constant. We the construct semiclassical waveforms on Lagrangian
submanifolds using the properties of the Leray-Maslov index, which allows us to
define the argument of the square root of a de Rham form.Comment: no figures. to appear in J. Phys. Math A. (2002
Isotopic and velocity distributions of Bi produced in charge-pickup reactions of 208Pb at 1 A GeV
Isotopically resolved cross sections and velocity distributions have been
measured in charge-pickup reactions of 1 A GeV 208Pb with proton, deuterium and
titanium target. The total and partial charge-pickup cross sections in the
reactions 208Pb + 1H and 208Pb + 2H are measured to be the same in the limits
of the error bars. A weak increase in the total charge-pickup cross section is
seen in the reaction of 208Pb with the titanium target. The measured velocity
distributions show different contributions - quasi-elastic scattering and
Delta-resonance excitation - to the charge-pickup production. Data on total and
partial charge-pickup cross sections from these three reactions are compared
with other existing data and also with model calculations based on the coupling
of different intra-nuclear cascade codes and an evaporation code.Comment: 20 pages, 12 figures, background information on
http://www-w2k.gsi.de/kschmidt
Asymptotic description of solutions of the exterior Navier Stokes problem in a half space
We consider the problem of a body moving within an incompressible fluid at
constant speed parallel to a wall, in an otherwise unbounded domain. This
situation is modeled by the incompressible Navier-Stokes equations in an
exterior domain in a half space, with appropriate boundary conditions on the
wall, the body, and at infinity. We focus on the case where the size of the
body is small. We prove in a very general setup that the solution of this
problem is unique and we compute a sharp decay rate of the solution far from
the moving body and the wall
About Starobinsky inflation
It is believed that soon after the Planck era, space time should have a
semi-classical nature. According to this, the escape from General Relativity
theory is unavoidable. Two geometric counter-terms are needed to regularize the
divergences which come from the expected value. These counter-terms are
responsible for a higher derivative metric gravitation. Starobinsky idea was
that these higher derivatives could mimic a cosmological constant. In this work
it is considered numerical solutions for general Bianchi I anisotropic
space-times in this higher derivative theory. The approach is ``experimental''
in the sense that there is no attempt to an analytical investigation of the
results. It is shown that for zero cosmological constant , there are
sets of initial conditions which form basins of attraction that asymptote
Minkowski space. The complement of this set of initial conditions form basins
which are attracted to some singular solutions. It is also shown, for a
cosmological constant that there are basins of attraction to a
specific de Sitter solution. This result is consistent with Starobinsky's
initial idea. The complement of this set also forms basins that are attracted
to some type of singular solution. Because the singularity is characterized by
curvature scalars, it must be stressed that the basin structure obtained is a
topological invariant, i.e., coordinate independent.Comment: Version accepted for publication in PRD. More references added, a few
modifications and minor correction
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