221 research outputs found
Classical Strongly Coupled QGP: VII. Shear Viscosity and Self Diffusion
We construct the Liouville operator for the SU(2) classical colored Coulomb
plasma (cQGP) for arbitrary values of the Coulomb coupling , the
ratio of the mean Coulomb to kinetic energy. We show that its resolvent in the
classical colored phase space obeys a hierarchy of equations. We use a free
streaming approximation to close the hierarchy and derive an integral equation
for the time-dependent structure factor. Its reduction by projection yields
hydrodynamical equations in the long-wavelength limit. We discuss the character
of the hydrodynamical modes at strong coupling. The shear viscosity is shown to
exhibit a minimum at near the liquid point. This minimum
follows from the cross-over between the single particle collisional regime
which drops as and the hydrodynamical collisional regime which
rises as . The self-diffusion constant drops as
irrespective of the regime. We compare our results to molecular dynamics
simulations of the SU(2) colored Coulomb plasma. We also discuss the relevance
of our results for the quantum and strongly coupled quark gluon plasma (sQGP)Comment: 36 pages, 14 figure
Classical Strongly Coupled QGP II: Screening and Equation of State
We analyze the screening and bulk energy of a classical and strongly
interacting plasma of color charges, a model we recently introduced for the
description of a quark-gluon plasma at T=(1-3)Tc. The partition function is
organized around the Debye-Huckel limit. The linear Debye-Huckel limit is
corrected by a virial expansion. For the pressure, the expansion is badly
convergent even in the dilute limit. The non-linear Debye-Huckel theory is
studied numerically as an alternative for moderately strong plasmas. We use
Debye theory of solid to extend the analysis to the crystal phase at very
strong coupling. The analytical results for the bulk energy per particle
compare well with the numerical results from molecular dynamics simulation for
all couplings.Comment: 9 pages, 5 figure
Rethinking the Properties of the Quark-Gluon Plasma at
We argue that although at asymptotically high temperatures the QGP in bulk
behaves as a gas of weakly interacting quasiparticles (modulo long-range
magnetism), at temperatures up to few times the critical temperature it
displays different properties. If the running of the QCD coupling constant
continues in the Coulomb phase till the screening length scale, it reaches the
strong coupling treshold . As a result, the Coulomb phase
supports weakly bound Coulombic s-wave , light quark and even
states.
The existence of shallow bound states dramatically increases the
quasiparticle rescattering at low energies, reducing the viscosity and thereby
explaining why heavy ion collisions at RHIC exhibit robust collective
phenomena. In conformal gauge theories at finite temperature the Coulomb
binding persists further in the strong coupling regime, as found for SUSY YM in the Maldacena regime.Comment: v2 version have one more figure and one more reference, v3 is the
same as v2 except a double-page format (the v2 had corrupted last lines on
the page
Classical Strongly Coupled QGP I: The Model and Molecular Dynamics Simulations
We propose a model for the description of strongly interacting quarks and
gluon quasiparticles at , as a classical and nonrelativistic
colored Coulomb gas. The sign and strength of the inter-particle interactions
are fixed by the scalar product of their classical {\it color vectors} subject
to Wong's equations. The model displays a number of phases as the Coulomb
coupling is increased ranging from a gas, to a liquid, to a crystal with
antiferromagnetic-like color ordering. We analyze the model using Molecular
Dynamics (MD) simulations and discuss the density-density correlator in real
time. We extract pertinent decorrelation times, diffusion and viscosity
constants for all phases. The classical results when extrapolated to the sQGP
suggest that the phase is liquid-like, with a diffusion constant and a bulk viscosity to entropy density ratio .Comment: 11 pages, 14 figure
Potassium channels in cell cycle and cell proliferation
Normal cell-cycle progression is a crucial task for every multicellular organism, as it determines body size and shape, tissue renewal and senescence, and is also crucial for reproduction. On the other hand, dysregulation of the cell-cycle progression leading to uncontrolled cell proliferation is the hallmark of cancer. Therefore, it is not surprising that it is a tightly regulated process, with multifaceted and very complex control mechanisms. It is now well established that one of those mechanisms relies on ion channels, and in many cases specifically on potassium channels. Here, we summarize the possible mechanisms underlying the importance of potassium channels in cell-cycle control and briefly review some of the identified channels that illustrate the multiple ways in which this group of proteins can influence cell proliferation and modulate cell-cycle progression
Classical strongly coupled QGP: VI. Structure Factors
We show that the classical and strongly coupled QGP (cQGP) is characterized
by a multiple of structure factors that obey generalized Orstein-Zernicke
equations. We use the canonical partition function and its associated density
functional to derive analytical equations for the density and charge monopole
structure factors for arbitrary values of , the ratio of the mean
potential to Coulomb energy. The results are compared with SU(2) molecular
dynamics simulations.Comment: 18 pages, 11 figure
Dilepton and Photon Emission Rates from a Hadronic Gas III
We extend our early analyses of the dilepton and photon emission rates from a
hadronic gas to account for strange mesons using a density expansion. The
emission rates are reduced to vacuum correlation functions using three-flavor
chiral reduction formulas, and the latters are assessed in terms of empirical
data. Using a fire-ball, we compare our results to the low and intermediate
mass dilepton data available from CERN. Our results suggest that a baryon free
hadronic gas does not account for the excess of low mass dielectrons observed
at CERES but do well in accounting for the intermediate dimuons at HELIOS. The
same observations apply to the recent low and high dielectron rates from
CERES.Comment: 12 pages LaTeX, 11 eps figure
Semiclassical Double-Pomeron Production of Glueballs and
A semiclassical theory of high energy scattering based on interrupted
tunneling (instantons) or QCD sphaleron production has been recently developed
to describe the growing hadronic cross section and properties of the soft
Pomeron. In this work we address double-pomeron processes in this framework for
the first time. We specifically derive the cross section for central production
of parity even and odd clusters, scalar and pseudoscalar glueballs, and
in parton-parton scattering at high energy. We show that the specific
dependence of the production cross section on all its kinematical variables
compares favorably with the UA8 data on inclusive cluster production, as well
as the WA102 data on exclusive central production of scalar glueball and
, in double-pomeron exchange scattering. The magnitude of the cross
section and its dependece on kinematic variables is correct, explaining in
particular a large deviation from the Pomeron factorization at cluster masses
in the range GeV reported by UA8
Level Crossing Analysis of Growing surfaces
We investigate the average frequency of positive slope ,
crossing the height in the surface growing processes. The
exact level crossing analysis of the random deposition model and the
Kardar-Parisi-Zhang equation in the strong coupling limit before creation of
singularities are given.Comment: 5 pages, two column, latex, three figure
The Skyrme model predictions for the mass spectrum and the - mass splittings
The -plet mass spectrum and the - mass splittings are computed in the framework of the minimal SU(3)
extended Skyrme model. As functions of the Skyrme charge and the SU(3)
symmetry breaking parameters the predictions are presented in tabular form. The
predicted mass splitting - is the smallest among
all SU(3) baryonic multiplets.Comment: 4 pages, 2 tables, version to appear in Phys. Rev.
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