36 research outputs found
Mean Field Dynamics in Non-Abelian Plasmas from Classical Transport Theory
Based on classical transport theory, we present a general set of covariant
equations describing the dynamics of mean fields and their statistical
fluctuations in a non-Abelian plasma in or out-of-equilibrium. A procedure to
obtain the collision integrals for the Boltzmann equation from the microscopic
theory is described. As an application, we study a hot non-Abelian plasma close
to equilibrium, where the fluctuations are integrated out explicitly. For soft
fields, and at logarithmic accuracy, we obtain B\"odeker's effective theory.Comment: 4 pages, revtex, no figures. Typo removed, a reference updated,
version as to appear in Phys. Rev. Let
Heavy Quark Radiative Energy Loss - Applications to RHIC
Heavy quark energy loss in a hot QCD plasma is computed taking into account
the competing effects due to suppression of zeroth order gluon radiation bellow
the plasma frequency and the enhancement of gluon radiation due to transition
energy loss and medium induced Bremsstrahlung. Heavy quark medium induced
radiative energy loss is derived to all orders in opacity, .
Numerical evaluation of the energy loss suggest small suppression of high
charm quarks, and therefore provide a possible explanation for the
null effects observed by PHENIX in the prompt electron spectrum in as
and 200 AGeV.Comment: 4 pages, 4 figures, Contributed to 17th International Conference on
Ultra Relativistic Nucleus-Nucleus Collisions (Quark Matter 2004), Oakland,
California, 11-17 Jan 200
Transport Theory of Massless Fields
Using the Schwinger-Keldysh technique we discuss how to derive the transport
equations for the system of massless quantum fields. We analyse the scalar
field models with quartic and cubic interaction terms. In the model
the massive quasiparticles appear due to the self-interaction of massless bare
fields. Therefore, the derivation of the transport equations strongly resembles
that one of the massive fields, but the subset of diagrams which provide the
quasiparticle mass has to be resummed. The kinetic equation for the finite
width quasiparticles is found, where, except the mean-field and collision
terms, there are terms which are absent in the standard Boltzmann equation. The
structure of these terms is discussed. In the massless model the
massive quasiparticles do not emerge and presumably there is no transport
theory corresponding to this model. It is not surprising since the
model is anyhow ill defined.Comment: 32 pages, no macro
Non-Abelian Excitations of the Quark-Gluon Plasma
We present new, non-abelian, solutions to the equations of motion which
describe the collective excitations of a quark-gluon plasma at high
temperature. These solutions correspond to spatially uniform color
oscillations.Comment: 8 pages LaTex, 1 figure (not included; available upon request),
Saclay preprint T94/0
Decoherence and energy loss in QCD cascades in nuclear collisions
The medium modifications in the properties of QCD cascades are considered. In
particular, the changes in the intrajet rapidity distributions due to
medium-induced decoherence, collisional losses of cascade gluons and those of
final prehadrons are analyzed
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.
Color conductivity and ladder summation in hot QCD
The color conductivity is computed at leading logarithmic order using a Kubo
formula. We show how to sum an infinite series of planar ladder diagrams,
assuming some approximations based on the dominance of soft scattering
processes between hard particles in the plasma. The result agrees with the one
obtained previously from a kinetical approach.Comment: 15 pages, 4 figures. Explanations enlarged, two figures and some refs
added, typos corrected. Final version to be published in Phys.Rev.
Classical Gluon Radiation in Ultrarelativistic Nuclear Collisions: Space-Time Structure, Instabilities, and Thermalization
We investigate the space-time structure of the classical gluon field produced
in an ultrarelativistic collision between color charges. The classical solution
which was computed previously in a perturbative approach is shown to become
unstable on account of the non-Abelian self-interaction neglected in the
perturbative solution scheme. The time scale for growth of the instabilities is
found to be of the order of the distance between the colliding color charges.
We argue that these instabilities will eventually lead to thermalization of
gluons produced in an ultrarelativistic collision between heavy nuclei. The
rate of thermalization is estimated to be of order , where is the
strong coupling constant and the transverse color charge density of an
ultrarelativistic nucleus.Comment: 11 pages, REVTeX, eps-, aps-, and psfig-style files, 7 figs., figs.
2-5 in gif-format, a uucompressed version of this paper including all figures
(ca. 2.2 Mb) is available at ftp://nt1.phys.columbia.edu/pub/stabil/stab.u
Longitudinal subtleties in diffusive Langevin equations for non-Abelian plasmas
Boedeker has recently argued that non-perturbative processes in very high
temperature non-Abelian plasmas (such as electroweak baryon number violation in
the very hot early Universe) can be quantitatively described, to leading
logarithmic accuracy, by a simple diffusive effective theory. Boedeker's
effective theory is intended to describe the long-distance transverse electric
and magnetic fields which are responsible for non-perturbative dynamics. His
effective theory, however, also contains long-wavelength longitudinal electric
fields. We discuss several subtleties in the treatment of longitudinal dynamics
which were not closely examined in Boedeker's original treatment. Somewhat to
our surprise, we find that within its domain of validity Boedeker's effective
theory does correctly describe both longitudinal and transverse fluctuations.
We also show that, as far as the transverse dynamics of interest is concerned,
Boedeker's effective theory could be replaced by a transverse-only theory that
removes the longitudinal dynamics altogether. In the process, we discuss
several interesting aspects of stochastic field theories.Comment: 29 pages, Section III rewritten, other minor change
From colored glass condensate to gluon plasma: equilibration in high energy heavy ion collisions
The initial distribution of gluons at the very early times after a high
energy heavy ion collision is described by the bulk scale of gluon
saturation in the nuclear wavefunction. The subsequent evolution of the system
towards kinetic equilibrium is described by a non-linear Landau equation for
the single particle distributions \cite{Mueller1,Mueller2}. In this paper, we
solve this equation numerically for the idealized initial conditions proposed
by Mueller, and study the evolution of the system to equilibrium. We discuss
the sensitivity of our results on the dynamical screening of collinear
divergences. In a particular model of dynamical screening, the convergence to
the hydrodynamic limit is seen to be rapid relative to hydrodynamic time
scales. The equilibration time, the initial temperature, and the chemical
potential are shown to have a strong functional dependence on the initial gluon
saturation scale .Comment: 34 pages, 10 figure