14 research outputs found
Classical and quantum many-body description of bremsstrahlung in dense matter (Landau - Pomeranchuk - Migdal effect)
Some considerations about the importance of coherence effects for
bremsstrahlung processes in non--equilibrium dense matter (Landau - Pomeranchuk
- Migdal - effect) are presented. They are of particular relevance for the
application to photon - and di-lepton production from high energy nuclear
collisions, to gluon radiation in QCD transport, or parton kinetics and to
neutrino and axion radiation from supernova explosion and from hot neutron
stars. The soft behavior of the bremsstrahlung from a source described by
classical transport models is discussed and pocket correction formulas for the
in-matter radiation cross sections are suggested in terms of standard transport
coefficients. The radiation rates are also discussed within a non--equilibrium
quantum field theory (Schwinger - Kadanoff - Baym - Keldysh) formulation. A
classification of diagrams and corresponding resummation in physically
meaningful terms is proposed, which considers the finite damping width of all
source particles in matter. This way each diagram in this expansion is already
free from the infra--red divergences. Both, the correct quasi--particle and
quasi--classical limits are recovered from this subset of graphs. Explicit
results are given for dense matter in thermal equilibrium. The diagrammatic
description may suggest a formulation of a transport theory that includes the
propagation of off--shell particles in non--equilibrium dense matter.Comment: 50 pages, submitted to Ann. Phys. (N. Y.); diagrams coded as
tex-macros; 5 figures available at:
ftp://tpri6b.gsi.de/pub/knoll/ap-95-fig.uu; paper as postscript file
(compressed and uuencoded) available at:
ftp://tpri6b.gsi.de/pub/knoll/ap-95.p
NON-EQUILIBRIUM DESCRIPTION OF BREMSSTRAHLUNG IN DENSE MATTER (Landau - Pomeranchuk - Migdal Effect)
The soft behavior of the bremsstrahlung from a source is discussed in terms
of classical transport models and within a non--equilibrium quantum field
theory (Schwinger - Kadanoff - Baym - Keldysh) formulation.Comment: 8 pages, latex, no figures (diagrams in latex
Kaon Condensation and the Non-Uniform Nuclear Matter
Non-uniform structures of nuclear matter are studied in a wide density-range.
Using the density functional theory with a relativistic mean-field model, we
examine non-uniform structures at sub-nuclear densities (nuclear ``pastas'')
and at high densities, where kaon condensate is expected. We try to give a
unified view about the change of the matter structure as density increases,
carefully taking into account the Coulomb screening effects from the viewpoint
of first-order phase transition.Comment: Presented at "Tours Symposium on Nuclear Physics V
Coulomb screening effect on the nuclear-pasta structure
Using the density functional theory (DFT) with the relativistic mean field
(RMF) model, we study the non-uniform state of nuclear matter, ``nuclear
pasta''. We self-consistently include the Coulomb interaction together with
other interactions. It is found that the Coulomb screening effect is
significant for each pasta structure but not for the bulk equation of state
(EOS) of the nuclear pasta phase
Finite size effects on kaonic pasta structures
Non-uniform structures of mixed phases at the first-order phase transition to
charged kaon condensation are studied using a density functional theory within
the relativistic mean field model. Including electric field effects and
applying the Gibbs conditions in a proper way, we numerically determine density
profiles of nucleons, electrons and condensed kaons. Importance of charge
screening effects is elucidated and thereby we show that the Maxwell
construction is effectively justified. Surface effect is also studied to figure
out its effect on the density profiles
Nuclear pasta structures and the charge screening effect
Non uniform structures of the nucleon matter at subnuclear densities are
numerically studied by means of the density functional theory with relativistic
mean-fields coupled with the electric field. A particular role of the charge
screening effects is demonstrated.Comment: 11 pages, 9 figures, submitted to PR
Resonance states below pion-nucleon threshold and their consequences for nuclear systems
Regular sequences of narrow peaks have been observed in the missing mass
spectra in the reactions pp --> p pi^+ X and pd --> ppX_1 below pion-production
threshold. They are interpreted in the literature as manifestations of
supernarrow light dibaryons, or nucleon resonances, or light pions forming
resonance states with the nucleon in its ground state. We discuss how existence
of such exotic states would affect properties of nuclear systems. We show that
the neutron star structure is drastically changed in all three cases. We find
that in the presence of dibaryons or nucleon resonances the maximal possible
mass of a neutron star would be smaller than the observational limit. Presence
of light pions does not contradict the observed neutron star masses. Light
pions allow for the existence of extended nuclear objects of arbitrary size,
bound by strong and electromagnetic forces.Comment: preprint ECT*-02-18, 6 pages, 3 figure
Negative Kaons in Dense Baryonic Matter
Kaon polarization operator in dense baryonic matter of arbitrary isotopic
composition is calculated including s- and p-wave kaon-baryon interactions. The
regular part of the polarization operator is extracted from the realistic
kaon-nucleon interaction based on the chiral and 1/N_c expansion. Contributions
of the Lambda(1116), Sigma(1195), Sigma*(1385) resonances are taken explicitly
into account in the pole and regular terms with inclusion of mean-field
potentials. The baryon-baryon correlations are incorporated and fluctuation
contributions are estimated. Results are applied for K- in neutron star matter.
Within our model a second-order phase transition to the s-wave K- condensate
state occurs at rho_c \gsim 4 \rho_0 once the baryon-baryon correlations are
included. We show that the second-order phase transition to the p-wave
condensate state may occur at densities in
dependence on the parameter choice. We demonstrate that a first-order phase
transition to a proton-enriched (approximately isospin-symmetric) nucleon
matter with a p-wave K- condensate can occur at smaller densities, \rho\lsim 2
\rho_0. The transition is accompanied by the suppression of hyperon
concentrations.Comment: 41 pages, 24 figures, revtex4 styl