1,032 research outputs found
Kinetics of the chiral phase transition in a linear model
We study the dynamics of the chiral phase transition in a linear quark-meson
model using a novel approach based on semiclassical wave-particle
duality. The quarks are treated as test particles in a Monte-Carlo simulation
of elastic collisions and the coupling to the meson, which is treated
as a classical field. The exchange of energy and momentum between particles and
fields is described in terms of appropriate Gaussian wave packets. It has been
demonstrated that energy-momentum conservation and the principle of detailed
balance are fulfilled, and that the dynamics leads to the correct equilibrium
limit. First schematic studies of the dynamics of matter produced in heavy-ion
collisions are presented.Comment: 15 pages, 12 figures, accepted by EPJA, dedicated to memory of Walter
Greiner; v2: corrected typos, added references and an acknowledgmen
Renormalization in Self-Consistent Approximation schemes at Finite Temperature III: Global Symmetries
We investigate the symmetry properties for Baym's -derivable schemes.
We show that in general the solutions of the dynamical equations of motion,
derived from approximations of the -functional, do not fulfill the
Ward-Takahashi identities of the symmetry of the underlying classical action,
although the conservation laws for the expectation values of the corresponding
Noether currents are fulfilled exactly for the approximation. Further we prove
that one can define an effective action functional in terms of the
self-consistent propagators which is invariant under the operation of the same
symmetry group representation as the classical action. The requirements for
this theorem to hold true are the same as for perturbative approximations: The
symmetry has to be realized linearly on the fields and it must be free of
anomalies, i.e., there should exist a symmetry conserving regularization
scheme. In addition, if the theory is renormalizable in Dyson's narrow sense,
it can be renormalized with counter terms which do not violate the symmetry.Comment: 32 papges, 3 figures, uses ReVTeX 4, V2: Added one more reference,
V3: Corrected some typos, added two more sections about the large-N expansio
Physical Activity and Adiposity Markers at Older Ages: Accelerometer Vs Questionnaire Data
Physical activity is critically important for successful aging, but its effect on adiposity markers at older ages is unclear as much of the evidence comes from self-reported data on physical activity. We assessed the associations of questionnaire-assessed and accelerometer-assessed physical activity with adiposity markers in older adults
Renormalization of Self-consistent Approximation schemes Finite Temperature II: Applications to the Sunset Diagram
The theoretical concepts for the renormalization of self-consistent Dyson
resummations, deviced in the first paper of this series, are applied to first
example cases for the -theory. Besides the tadpole (Hartree)
approximation as a novel part the numerical solutions are presented which
includes the sunset self-energy diagram into the self-consistent scheme based
on the -derivable approximation or 2PI effective action concept.Comment: 18 pages, 7 figures Changes in version 2: Adapted title to the first
paper of the series, added one figure and some references. This version was
submitted to Phys. Rev. D; Changes in version 3: added one more reference
Changes in version 4 (accepted for publication by Phys. Rev. D): Added a
paragraph about the massless case and some remarks in the introductio
Non-perturbative construction of counterterms for 2PI-approximation
A concise method is presented for the non-perturbative computation of the
counterterms renormalising 2PI-actions. The procedure is presented for a real
scalar field up to lambda^2 order in the skeleton truncation of Gamma_2PI with
respect to the self-coupling, and in a constant symmetry breaking background.
The method is easily generalizable to field theories with arbitrary global
symmetry.Comment: 4 pages, poster presented at Strong and Electroweak Matter
(SEWM2008), Amsterdam,August 25-29 200
Transport properties and Langevin dynamics of heavy quarks and quarkonia in the Quark Gluon Plasma
Quark Gluon Plasma transport coefficients for heavy quarks and
quark-antiquark pairs are computed through an extension of the results obtained
for a hot QED plasma by describing the heavy-quark propagation in the eikonal
approximation and by weighting the gauge field configurations with the Hard
Thermal Loop effective action. It is shown that such a model allows to
correctly reproduce, at leading logarithmic accuracy, the results obtained by
other independent approaches. The results are then inserted into a relativistic
Langevin equation allowing to follow the evolution of the heavy-quark momentum
spectra. Our numerical findings are also compared with the ones obtained in a
strongly-coupled scenario, namely with the transport coefficients predicted
(though with some limitations and ambiguities) by the AdS/CFT correspondence.Comment: Minor changes. One figure added. Final version accepted for
publication by Nucl. Phys.
Heavy-Quark Diffusion, Flow and Recombination at RHIC
We discuss recent developments in assessing heavy-quark interaction in the
Quark-Gluon Plasma (QGP). While induced gluon radiation is expected to be the
main energy-loss mechanism for fast-moving quarks, we focus on elastic
scattering which prevails toward lower energies, evaluating both perturbative
(gluon-exchange) and nonperturbative (resonance formation) interactions in the
QGP. The latter are treated within an effective model for D- and B-meson
resonances above T_c as motivated by current QCD lattice calculations.
Pertinent diffusion and drag constants, following from a Fokker-Planck
equation, are implemented into an expanding fireball model for Au-Au collisions
at RHIC using relativistic Langevin simulations. Heavy quarks are hadronized in
a combined fragmentation and coalescence framework, and resulting
electron-decay spectra are compared to recent RHIC data. A reasonable
description of both nuclear suppression factors and elliptic flow up to momenta
of ~5 GeV supports the notion of a strongly interacting QGP created at RHIC.
Consequences and further tests of the proposed resonance interactions are
discussed.Comment: 8 pages, 14 figures, contribution to the proceedings for the
"International Conference on Strangeness in Quark Matter 2006
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