8,389 research outputs found
Anomalous Transport Processes in Anisotropically Expanding Quark-Gluon Plasmas
We derive an expression for the anomalous viscosity in an anisotropically
expanding quark-gluon-plasma, which arises from interactions of thermal partons
with dynamically generated color fields. The anomalous viscosity dominates over
the collisional viscosity for large velocity gradients or weak coupling. This
effect may provide an explanation for the apparent ``nearly perfect'' liquidity
of the matter produced in nuclear collisions at RHIC without the assumption
that it is a strongly coupled state.Comment: 31 pages, 1 figure, some typos in published version are correcte
Synthesis of imide/arylene ether copolymers for adhesives and composite matrices
A series of imide/arylene ether copolymers were prepared from the reaction of an amorphous arylene ether oligomer and a semi-crystalline imide oligomer. These copolymers were thermally characterized and mechanical properties were measured. One block copolymer was endcapped and the molecular weight was controlled to provide a material that displayed good compression moldability and attractive adhesion and composite properties
Anomalous Viscosity of an Expanding Quark-Gluon Plasma
We argue that an expanding quark-gluon plasma has an anomalous viscosity,
which arises from interactions with dynamically generated color fields. We
derive an expression for the anomalous viscosity in the turbulent plasma domain
and apply it to the hydrodynamic expansion phase, when the quark-gluon plasma
is near equilibrium. The anomalous viscosity dominates over the collisional
viscosity for weak coupling and not too late times. This effect may provide an
explanation for the apparent ``nearly perfect'' liquidity of the matter
produced in nuclear collisions at the Relativistic Heavy Ion Collider without
the assumption that it is a strongly coupled state.Comment: Final version accepted for publicatio
Transverse Momentum in Semi-Inclusive Polarized Deep Inelastic Scattering and the Spin-Flavor Structure of the Proton
The non-valence spin-flavor structure of the nucleon extracted from
semi-inclusive measurements of polarized deep inelastic scattering depends
strongly on the transverse momentum of the detected hadrons which are used to
determine the individual polarized sea distributions. This physics may explain
the recent HERMES observation of a positively polarized strange sea through
semi-inclusive scattering, in contrast to the negative strange sea polarization
deduced from inclusive polarized deep inelastic scattering.Comment: 4 pages, revtex style, 2 figure
Splittings of generalized Baumslag-Solitar groups
We study the structure of generalized Baumslag-Solitar groups from the point
of view of their (usually non-unique) splittings as fundamental groups of
graphs of infinite cyclic groups. We find and characterize certain
decompositions of smallest complexity (`fully reduced' decompositions) and give
a simplified proof of the existence of deformations. We also prove a finiteness
theorem and solve the isomorphism problem for generalized Baumslag-Solitar
groups with no non-trivial integral moduli.Comment: 20 pages; hyperlinked latex. Version 2: minor change
An explicit KO-degree map and applications
The goal of this note is to study the analog in unstable -homotopy theory of the unit map from the motivic sphere spectrum to the
Hermitian K-theory spectrum, i.e., the degree map in Hermitian K-theory. We
show that "Suslin matrices", which are explicit maps from odd dimensional split
smooth affine quadrics to geometric models of the spaces appearing in Bott
periodicity in Hermitian K-theory, stabilize in a suitable sense to the unit
map. As applications, we deduce that for ,
which can be thought of as an extension of Matsumoto's celebrated theorem
describing of a field. These results provide the first step in a program
aimed at computing the sheaf for .Comment: 36 Pages, Final version, to appear Journal of Topolog
Possible Resolutions of the D-Paradox
We propose possible ways of explaining the net charge event-by-event
fluctuations in Au+Au collisions at the Relativistic Heavy Ion Collider within
a quark recombination model. We discuss various methods of estimating the
number of quarks at recombination and their implications for the predicted net
charge fluctuations. We also discuss the possibility of diquark and
quark-antiquark clustering above the deconfinement temperature.Comment: 5 pages, 2 figure
Intensity interferometry of thermal photons from relativistic heavy ion collisions
Intensity interferometry of thermal photons, having transverse momenta 0.1 -- 2.0 GeV, produced in relativistic collision of heavy nuclei is
studied. It is seen to provide an accurate information about the temporal and
spatial structure of the interacting system. The source dimensions and their
dependence revealed by the photon interferometry, display a richness not
seen in pion interferometry. We attribute this to difference in the source
functions, the fact that photons come out from every stage of the collision and
from every point in the system, and the fact that the rate of production of
photons is different for the quark-gluon plasma, which dominates the early hot
stage, and the hadronic matter which populates the last phase of the collision
dynamics. The usefulness of this procedure is demonstrated by an application to
collision of lead nuclei at the CERN SPS. Prediction for the transverse
momentum dependence of the sizes for SPS, RHIC, and LHC energies are given.Comment: 16 pages, 11 figures. Added discussions and references. To appear in
Phys. Rev.
Event-by-event fluctuations of the charged particle ratio from non-equilibrium transport theory
The event by event fluctuations of the ratio of positively to negatively
charged hadrons are predicted within the UrQMD model. Corrections for finite
acceptance and finite net charge are derived. These corrections are relevant to
compare experimental data and transport model results to previous predictions.
The calculated fluctuations at RHIC and SPS energies are shown to be compatible
with a hadron gas. Thus, deviating by a factor of 3 from the predictions for a
thermalized quark-gluon plasma.Comment: This paper clarifies the previous predictions of Jeon and Koch
(hep-ph/0003168) and addresses issues raised in hep-ph/0006023. 2 Figures,
10pp, uses RevTe
Transverse Velocity Dependence of the Proton-Antiproton Ratio as a Signature of the QCD Critical Endpoint
The presence of a critical point in the QCD phase diagram can deform the
trajectories describing the evolution of the expanding fireball in the
phase diagram. If the average emission time of hadrons is a function
of transverse velocity, as microscopic simulations of the hadronic freeze-out
dynamics suggest, the deformation of the hydrodynamic trajectories will change
the transverse velocity () dependence of the proton-antiproton
ratio when the fireball passes in the vicinity of the critical point. An
unusual -dependence of the ratio in a narrow beam
energy window would thus signal the presence of the critical point.Comment: Final version accepted for publicatio
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