166 research outputs found
Neutrino-nucleon scattering rate in the relativistic random phase approximation
The in-medium modification to the neutrino-nucleon scattering rate is
calculated in the relativistic random phase approximation in the framework of a
hadronic meson exchange model, in view of applications to neutrino transport in
supernovae and protoneutron starsComment: 4 pages, 2 figures, to appear in the Proceedings of the PANIC02
conference, 30 sept - 4 oct 2002, Osaka, Japa
Neutron stars in a Skyrme model with hyperons
Available Skyrme parametrizations with hyperons are examined from the point
of view of their suitability for applications to neutron stars. It is shown
that the hyperons can attenuate or even remove the problem of ferromagnetic
instability common to (nearly) all Skyrme parametrizations of the
nucleon-nucleon interaction. At high density the results are very sensitive to
the choice of the Lambda-Lambda interaction. The selected parameter sets are
then used to obtain the resulting properties of both cold neutron stars and hot
protoneutron stars. The general features known from other models are recovered.Comment: 27 pages, 9 figure
Relativistic transport equations with generalized mass shell constraints
We reexamine the derivation of relativistic transport equations for fermions
when conserving the most general spinor structure of the interaction and Green
function. Such an extension of the formalism is needed when dealing with {\it
e.g.} spin-polarized nuclear matter or non-parity conserving interactions. It
is shown that some earlier derivations can lead to an incomplete description of
the evolution of the system even in the case of parity-conserving,
spin-saturated systems. The concepts of kinetic equation and mass shell
condition have to be extended, in particular both of them acquire a non trivial
spinor structure which describe a rich polarization dynamics.Comment: 11 pages, submitted to Proceedings KB99 Workshop, September 20-24
1999, Rostock, German
On the Role of Dissipation in the Early Stages of Relativistic Heavy Ion Collisions
The influence of the dissipative terms on the conditions of formation and the
characteristic parameters of shock waves in relativistic nuclear collisions is
investigated for three types of equation of state (non linear QHD-1, resonance
gas and lattice QCD). Energy and velocity profiles are obtained in a
one-dimensional model; the duration of the shock phase and width of the shock
front are calculated. It is shown that the presence of a phase transition
results in a strong enhancement of the width of the shock front, which results
in an increase of transparency. This effect, combined with the fact that the
nuclei have a finite size, prevents the energy density to rise to its maximum
value (full stopping) as would be predicted by a non dissipative shock model.Comment: 30 pages, 18 figures, uuencoded compressed postscript file (with
figures already embedded), submitted to Nucl. Phys.
Neutrino-nucleon scattering rate in proto neutron star matter
We present a calculation of the neutrino-nucleon scattering cross section
which takes into account the nuclear correlations in the relativistic random
phase approximation. Our approach is based on a quantum hadrodynamics model
with exchange of , , , and mesons. In view
of applications to neutrino transport in the final stages of supernova
explosion and protoneutron star cooling, we study the evolution of the neutrino
mean free path as a function of density, proton-neutron asymmetry and
temperature. Special attention was paid to the issues of renormalization of the
Dirac sea, residual interactions in the tensor channel and meson mixing. It is
found that RPA corrections, with respect to the mean field approximation,
amount to only 10% to 15% at high density.Comment: 20 pages, 9 figures, subm. to EPJ
Hyperon ordering in neutron star matter
We explore the possible formation of ordered phases in neutron star matter.
In the framework of a quantum hadrodynamics model where neutrons, protons and
Lambda hyperons interact via the exchange of mesons, we compare the energy of
the usually assumed uniform, liquid phase, to that of a configuration in which
di-lambda pairs immersed in an uniform nucleon fluid are localized on the nodes
of a regular lattice. The confining potential is calculated self-consistently
as resulting from the combined action of the nucleon fluid and the other
hyperons, under the condition of beta equilibrium. We are able to obtain stable
ordered phases for some reasonable sets of values of the model parameters. This
could have important consequences on the structure and cooling of neutron
stars.Comment: 6 pages, 2 figures. To appear in the proceedings of the 4th Catania
Relativistic Ion Studies: Exotic Clustering (CRIS 2002), Catania, Italy,
10-14 Jun 200
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