159 research outputs found
Relativistic Kinetic Equations for Electromagnetic, Scalar and Pseudoscalar Interactions
We derive the kinetic equations for both the covariant and equal-time Wigner
functions of Dirac particles with electromagnetic, scalar and pseudoscalar
interactions. We emphasize the constraint equations for the spinor components
in the equal-time formulation.Comment: 12 pages, no figures, revte
Coherent photon bremsstrahlung and dynamics of heavy-ion collisions: comparison of different models
Differential spectra of coherent photon bremsstrahlung in relativistic heavy
ion collisions are calculated within various schematic models of the
projectile-target stopping. Two versions of the degradation length model, based
on a phenomenological deceleration law, are considered. The simple shock wave
model is studied analytically. The predictions of these models agree in the
soft photon limit, where the spectrum is determined only by the final velocity
distribution of charged particles. The results of these models in the case of
central Au+Au collisions at various bombarding energies are compared with the
predictions of the microscopic transport model UrQMD. It is shown that at the
AGS energy the coherent photon bremsstrahlung exceeds the photon yield from
-decays at photon energies \omega\loo 50 MeV.Comment: 23 pages RevTeX, 9 eps Figure
Color plasma oscillation in strangelets
The dispersion relation and damping rate of longitudinal color plasmons in
finite strange quark matter (strangelets) are evaluated in the limits of weak
coupling, low temperature, and long wavelength. The property of the QCD vacuum
surrounding a strangelet makes the frequency of the plasmons nearly the same as
the color plasma frequency of bulk matter. The plasmons are damped by their
coupling with individual excitations of particle-hole pairs of quarks, of which
the energy levels are discretized by the boundary. For strangelets of
macroscopic size, the lifetime of the plasmons is found to be proportional to
the size, as in the case of the usual plasma oscillations in metal
nanoparticles.Comment: 9 pages (REVTeX), 2 Postscript figures, to be published in Phys. Rev.
Comparison of the NMR solution structure and the x-ray crystal structure of rat metallothionein-2.
A New Non-Perturbative Approach to Quantum Theory in Curved Spacetime Using the Wigner Function
A new non-perturbative approach to quantum theory in curved spacetime and to
quantum gravity, based on a generalisation of the Wigner equation, is proposed.
Our definition for a Wigner equation differs from what have otherwise been
proposed, and does not imply any approximations. It is a completely exact
equation, fully equivalent to the Heisenberg equations of motion. The approach
makes different approximation schemes possible, e.g. it is possible to perform
a systematic calculation of the quantum effects order by order. An iterative
scheme for this is also proposed. The method is illustrated with some simple
examples and applications. A calculation of the trace of the renormalised
energy-momentum tensor is done, and the conformal anomaly is thereby related to
non-conservation of a current in d=2 dimensions and a relationship between a
vector and an axial-vector current in d=4 dimensions.
The corresponding ``hydrodynamic equations'' governing the evolution of
macroscopic quantities are derived by taking appropriate moments. The emphasis
is put on the spin-1/2 case, but it is shown how to extend to arbitrary spins.
Gravity is treated first in the Palatini formalism, which is not very
tractable, and then more successfully in the Ashtekar formalism, where the
constraints lead to infinite order differential equations for the Wigner
functions.Comment: LaTeX2e (uses amssymb), 36 page
Chiral phase properties of finite size quark droplets in the Nambu--Jona-Lasinio model
Chiral phase properties of finite size hadronic systems are investigated
within the Nambu--Jona-Lasinio model. Finite size effects are taken into
account by making use of the multiple reflection expansion. We find that, for
droplets with relatively small baryon numbers, chiral symmetry restoration is
enhanced by the finite size effects. However the radius of the stable droplet
does not change much, as compared to that without the multiple reflection
expansion.Comment: RevTex4, 9 pages, 6 figures, to be published in Phys. Rev.
Physics and Astrophysics of Strange Quark Matter
3-flavor quark matter (strange quark matter; SQM) can be stable or metastable
for a wide range of strong interaction parameters. If so, SQM can play an
important role in cosmology, neutron stars, cosmic ray physics, and
relativistic heavy-ion collisions. As an example of the intimate connections
between astrophysics and heavy-ion collision physics, this Chapter gives an
overview of the physical properties of SQM in bulk and of small-baryon number
strangelets; discusses the possible formation, destruction, and implications of
lumps of SQM (quark nuggets) in the early Universe; and describes the structure
and signature of strange stars, as well as formation and detection of
strangelets in cosmic rays. It is concluded, that astrophysical and laboratory
searches are complementary in many respects, and that both should be pursued to
test the intriguing possibility of a strange ground state for hadronic matter,
and (more generally) to improve our knowledge of the strong interactions.Comment: 45 pages incl. figures. To appear in "Hadrons in Dense Matter and
Hadrosynthesis", Lecture Notes in Physics, Springer Verlag (ed. J.Cleymans
Equal-Time Hierarchies in Quantum Transport Theory
We investigate in the equal-time formalism the derivation and truncation of
infinite hierarchies of equations of motion for the energy moments of the
covariant Wigner function. From these hierarchies we then extract kinetic
equations for the physical distribution functions which are related to
low-order energy moments, and show how to determine the higher order moments in
terms of these lowest order ones. We apply the general formalism to scalar and
spinor QED with classical background fields and compare with the results
derived from the three-dimensional Wigner transformation method.Comment: 44 pages, no figure
The Council of Europe's Approach towards Ageism
In this chapter, I examine the degree of interest in ageism among Council of
Europe members, and the degree of interest in its elimination through the Council
of Europe forum. I also examine the interpretation of the concept of ageism by various
Council of Europe institutions. Finally, I explore the Council’s willingness and
ability to eliminate or at least mitigate ageism effect
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