150 research outputs found
A calculation of the transport coefficients of hot and dense hadronic matter based on the event generator URASiMA
We evaluate thermodynamical quantities and the transport coefficients of a
dense and hot hadronic matter based on the event generator URASiMA
(Ultra-Relativistic AA collision Simulator based on Multiple Scattering
Algorithm) with periodic boundary conditions. As the simplest example of the
transport coefficients we investigate the temperature dependence and the
chemical potential dependence of the baryon diffusion constant of a dense and
hot hadronic matter.Comment: To appear in the Proceeding of the International Conference on Quark
Nuclear Physics(QNP2000), 21-25 February 2000, Adelaide, Australi
Analyses of collective flow and space-time evolution based on relativistic hydrodynamical model
We numerically solve fully (3+1)-dimensional relativistic hydrodynamical
equation with the baryon number conservation law. For realistic initial
conditions we adopt the results from the event generator (URASiMA). Using this
model we discuss collective flow.Comment: 4 pages, 11 figures, to apper in Proceedings of Quark Matter '9
Non-Commutativity of the Zero Chemical Potential Limit and the Thermodynamic Limit in Finite Density Systems
Monte Carlo simulations of finite density systems are often plagued by the
complex action problem. We point out that there exists certain
non-commutativity in the zero chemical potential limit and the thermodynamic
limit when one tries to study such systems by reweighting techniques. This is
demonstrated by explicit calculations in a Random Matrix Theory, which is
thought to be a simple qualitative model for finite density QCD. The
factorization method allows us to understand how the non-commutativity, which
appears at the intermediate steps, cancels in the end results for physical
observables.Comment: 7 pages, 9 figure
Effective Model Approach to the Dense State of QCD Matter
The first-principle approach to the dense state of QCD matter, i.e. the
lattice-QCD simulation at finite baryon density, is not under theoretical
control for the moment. The effective model study based on QCD symmetries is a
practical alternative. However the model parameters that are fixed by hadronic
properties in the vacuum may have unknown dependence on the baryon chemical
potential. We propose a new prescription to constrain the effective model
parameters by the matching condition with the thermal Statistical Model. In the
transitional region where thermal quantities blow up in the Statistical Model,
deconfined quarks and gluons should smoothly take over the relevant degrees of
freedom from hadrons and resonances. We use the Polyakov-loop coupled
Nambu--Jona-Lasinio (PNJL) model as an effective description in the quark side
and show how the matching condition is satisfied by a simple ansatz on the
Polyakov loop potential. Our results favor a phase diagram with the chiral
phase transition located at slightly higher temperature than deconfinement
which stays close to the chemical freeze-out points.Comment: 8 pages, 4 figures; Talk at International Workshop on High Density
Nuclear Matter, Cape Town, South Africa, April 6-9, 201
Instantons and Scalar Multiquark States: From Small to Large N_c
We study scalar quark-anti-quark and two-quark-two-anti-quark correlation
functions in the instanton liquid model. We show that the instanton liquid
supports a light scalar-isoscalar (sigma) meson, and that this state is
strongly coupled to both and . The scalar-isovector
meson, on the other hand, is heavy. We also show that these properties
are specific to QCD with three colors. In the large limit the
scalar-isoscalar meson is not light, and it is mainly coupled to .Comment: 24 page
Phase structures of strong coupling lattice QCD with finite baryon and isospin density
Quantum chromodynamics (QCD) at finite temperature (T), baryon chemical
potential (\muB) and isospin chemical potential (\muI) is studied in the strong
coupling limit on a lattice with staggered fermions. With the use of large
dimensional expansion and the mean field approximation, we derive an effective
action written in terms of the chiral condensate and pion condensate as a
function of T, \muB and \muI. The phase structure in the space of T and \muB is
elucidated, and simple analytical formulas for the critical line of the chiral
phase transition and the tricritical point are derived. The effects of a finite
quark mass (m) and finite \muI on the phase diagram are discussed. We also
investigate the phase structure in the space of T, \muI and m, and clarify the
correspondence between color SU(3) QCD with finite isospin density and color
SU(2) QCD with finite baryon density. Comparisons of our results with those
from recent Monte Carlo lattice simulations on finite density QCD are given.Comment: 18 pages, 6 figures, revtex4; some discussions are clarified, version
to appear in Phys. Rev.
Glueballs and the superfluid phase of Two-Color QCD
We present the first results on scalar glueballs in cold, dense matter using
lattice simulations of two color QCD. The simulations are carried out on a lattice and use a standard hybrid molecular dynamics algorithm for
staggered fermions for two values of quark mass. The glueball correlators are
evaluated via a multi-step smearing procedure. The amplitude of the glueball
correlator peaks in correspondence with the zero temperature chiral transition,
, and the propagators change in a significant way in the
superfluid phase, while the Polyakov loop is mearly insensitive to the
transition. Standard analysis suggest that lowest mass in the gluonic
channel decreases in the superfluid phase, but these observations need to be
confirmed on larger and more elongated lattices These results indicate that a
nonzero density induces nontrivial modifications of the gluonic medium.Comment: 26 pages, 13 figures; discussions and one figure added; to appear in
EPJ
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